|
Hello all,
I am completely new to oscilliscopes, and I just acquired one of these for free, since it was not working. Cool thing is that the technical manual is downloadable and the user manual as well, since this is a military unit.
Now the rub: I have never used an oscilliscope, and might not ever use one, however I'm learning electronics repair and my Dad is telling me that this could be an invaluable piece of troubleshooting equipment. Another problem is that you normally need a couple things to troubleshoot an oscilliscope, such as a frequency generator and - another oscilliscope.
I've used the flow chart on the technical manual and it appears that the horizontal signal board needs to be repaired. The CRT projects a beam only when I press the TEST button and only vertical adjustments are possible. Horizontal adjustments while holding the test? button down do nothing.
Anyone in the San Antonio TX area willing to help a newbie out? I work long hours (3am - 8pm mostly) so the time I get off is usually weekends.
|
Hi there
firstly welcome to the group but could you
please include your name at the end of your posting
Now to your problem?
You are very lucky that the military service
/ operating information includes the CCT diagrams ?I trust you Have
volumes 1 and 2
it appears that the AN/USM 281A is a ruggedized
version of the HP 180? and this is a very good old oscilloscope and very
reparable
?
At this time I suggest you repeat your posting
as HP 180 Oscilloscope needs help with repair this might receive more postings
The horizontal board is next to the tube
and has Very High voltage, The lack
of horizontal deflection is normally due to component frailer
the 2 drive transistors that provide the
deflection to the tube and there drivers are the usual ones that fail
?
regards Paul B????
south cost UK
From:
hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]
Sent: 07 October 2017 16:46
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] HP
AN/USM 281A Oscilliscope needs repair (San
Antonio TX)
?
?
Hello
all,
I am
completely new to oscilliscopes, and I just acquired one of these for free,
since it was not working. Cool thing is that the technical manual is
downloadable and the user manual as well, since this is a military unit.
Now the
rub: I have never used an oscilliscope, and might not ever use one, however I'm
learning electronics repair and my Dad is telling me that this could be an
invaluable piece of troubleshooting equipment. Another problem is that you
normally need a couple things to troubleshoot an oscilliscope, such as a
frequency generator and - another oscilliscope.
I've used
the flow chart on the technical manual and it appears that the horizontal
signal board needs to be repaired. The CRT projects a beam only when I press
the TEST button and only vertical adjustments are possible. Horizontal
adjustments while holding the test? button down do nothing.
Anyone in
the San Antonio TX area willing to help a newbie out? I work
long hours (3am - 8pm mostly) so the time I get off is usually weekends.
No virus found in this message.
Checked by AVG -
Version: 2016.0.8013 / Virus Database: 4782/15015 - Release Date: 10/07/17
|
Look to be sure you have switched to internal sweep, switch settings are good to double check.
Dennis
--------------------------------------------
toggle quoted message
Show quoted text
On Sat, 10/7/17, andremajic@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Saturday, October 7, 2017, 11:45 AM
Hello all,
I am completely new to oscilliscopes,
and I just acquired one of these for free, since it was not
working. Cool thing is that the technical manual is
downloadable and the user manual as well, since this is a
military unit.
Now the rub: I have never used an
oscilliscope, and might not ever use one, however I'm
learning electronics repair and my Dad is telling me that
this could be an invaluable piece of troubleshooting
equipment. Another problem is that you normally need a
couple things to troubleshoot an oscilliscope, such as a
frequency generator and - another
oscilliscope.
I've used the flow chart on the
technical manual and it appears that the horizontal signal
board needs to be repaired. The CRT projects a beam only
when I press the TEST button and only vertical adjustments
are possible. Horizontal adjustments while holding the
test? button down do nothing.
Anyone in the San Antonio TX area
willing to help a newbie out? I work long hours (3am - 8pm
mostly) so the time I get off is usually weekends.
|
"The horizontal board is next to the tube and has Very High voltage, The lack of horizontal deflection is normally due to component frailer the 2 drive transistors that provide the deflection to the tube and there drivers are the usual ones that fail."
I bought a mil surplus Dumont 1060 (dual trace 60 MHz) scope around 1990. A few weeks after the 30 day warranty expired, the horizontal sweep died. After tracing my way through the sweep circuit, the problem turned out to be fractured solder joints. The Dumont was a 60's design with socketed transistors as was the Tek 465 I used to repair the Dumont. Both had problems with bad solder joints and corroded transistor leads. I had an experienced Tek repairman take a look at the 465. He whacked the frame of the scope with a stick. I was a little shocked when he did that, but immediately realized it's the best way to check for intermittent connections. He started out by banging his hands on opposite sides of the instrument before taking the covers off. Just be careful that you don't damage anything when you hit it. I learned enough from the Tek guy to do the repairs on the 465 myself once I'd fixed the Dumont.
If the sweep appears for even a instant when you whack the scope frame you're hunting an intermittent. It's tedious, but it means you don't need to replace parts.
Whatever you do, do NOT spray tuner cleaner on the vertical input switches. That's very bad for the capacitors. I learned this AFTER I had done it and spent a lot of effort cleaning things with 99% isopropyl alcohol.
Good luck and have fun!
Reg
|
The troubleshooting flowchart on the manual says to replace two gallium transistors on that board.
I tried the whack test. Nothing.
I'm just thinking that maybe I don't have the settings right on the unit, because I'd feel really dumb to put work into replacing a board only to find I didn't have a switch turned on or a knob in the right setting.
Andrew
--------------------------------------------
toggle quoted message
Show quoted text
On Sun, 10/8/17, Reginald Beardsley pulaskite@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 9:19 AM
?
"The horizontal board is next to the tube and has Very
High voltage, The lack of horizontal deflection is normally
due to component frailer the 2 drive transistors that
provide the deflection to the tube and there drivers are the
usual ones that fail."
I bought a mil surplus Dumont 1060 (dual trace 60 MHz) scope
around 1990. A few weeks after the 30 day warranty expired,
the horizontal sweep died. After tracing my way through the
sweep circuit, the problem turned out to be fractured solder
joints. The Dumont was a 60's design with socketed
transistors as was the Tek 465 I used to repair the Dumont.
Both had problems with bad solder joints and corroded
transistor leads. I had an experienced Tek repairman take a
look at the 465. He whacked the frame of the scope with a
stick. I was a little shocked when he did that, but
immediately realized it's the best way to check for
intermittent connections. He started out by banging his
hands on opposite sides of the instrument before taking the
covers off. Just be careful that you don't damage
anything when you hit it. I learned enough from the Tek guy
to do the repairs on the 465 myself once I'd fixed the
Dumont.
If the sweep appears for even a instant when you whack the
scope frame you're hunting an intermittent. It's
tedious, but it means you don't need to replace
parts.
Whatever you do, do NOT spray tuner cleaner on the vertical
input switches. That's very bad for the capacitors. I
learned this AFTER I had done it and spent a lot of effort
cleaning things with 99% isopropyl alcohol.
Good luck and have fun!
Reg
#yiv1074488942 #yiv1074488942 --
#yiv1074488942ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv1074488942 #yiv1074488942ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv1074488942 #yiv1074488942ygrp-mkp #yiv1074488942hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv1074488942 #yiv1074488942ygrp-mkp #yiv1074488942ads {
margin-bottom:10px;}
#yiv1074488942 #yiv1074488942ygrp-mkp .yiv1074488942ad {
padding:0 0;}
#yiv1074488942 #yiv1074488942ygrp-mkp .yiv1074488942ad p {
margin:0;}
#yiv1074488942 #yiv1074488942ygrp-mkp .yiv1074488942ad a {
color:#0000ff;text-decoration:none;}
#yiv1074488942 #yiv1074488942ygrp-sponsor
#yiv1074488942ygrp-lc {
font-family:Arial;}
#yiv1074488942 #yiv1074488942ygrp-sponsor
#yiv1074488942ygrp-lc #yiv1074488942hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv1074488942 #yiv1074488942ygrp-sponsor
#yiv1074488942ygrp-lc .yiv1074488942ad {
margin-bottom:10px;padding:0 0;}
#yiv1074488942 #yiv1074488942actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv1074488942 #yiv1074488942activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv1074488942 #yiv1074488942activity span {
font-weight:700;}
#yiv1074488942 #yiv1074488942activity span:first-child {
text-transform:uppercase;}
#yiv1074488942 #yiv1074488942activity span a {
color:#5085b6;text-decoration:none;}
#yiv1074488942 #yiv1074488942activity span span {
color:#ff7900;}
#yiv1074488942 #yiv1074488942activity span
.yiv1074488942underline {
text-decoration:underline;}
#yiv1074488942 .yiv1074488942attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv1074488942 .yiv1074488942attach div a {
text-decoration:none;}
#yiv1074488942 .yiv1074488942attach img {
border:none;padding-right:5px;}
#yiv1074488942 .yiv1074488942attach label {
display:block;margin-bottom:5px;}
#yiv1074488942 .yiv1074488942attach label a {
text-decoration:none;}
#yiv1074488942 blockquote {
margin:0 0 0 4px;}
#yiv1074488942 .yiv1074488942bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv1074488942 .yiv1074488942bold a {
text-decoration:none;}
#yiv1074488942 dd.yiv1074488942last p a {
font-family:Verdana;font-weight:700;}
#yiv1074488942 dd.yiv1074488942last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv1074488942 dd.yiv1074488942last p
span.yiv1074488942yshortcuts {
margin-right:0;}
#yiv1074488942 div.yiv1074488942attach-table div div a {
text-decoration:none;}
#yiv1074488942 div.yiv1074488942attach-table {
width:400px;}
#yiv1074488942 div.yiv1074488942file-title a, #yiv1074488942
div.yiv1074488942file-title a:active, #yiv1074488942
div.yiv1074488942file-title a:hover, #yiv1074488942
div.yiv1074488942file-title a:visited {
text-decoration:none;}
#yiv1074488942 div.yiv1074488942photo-title a,
#yiv1074488942 div.yiv1074488942photo-title a:active,
#yiv1074488942 div.yiv1074488942photo-title a:hover,
#yiv1074488942 div.yiv1074488942photo-title a:visited {
text-decoration:none;}
#yiv1074488942 div#yiv1074488942ygrp-mlmsg
#yiv1074488942ygrp-msg p a span.yiv1074488942yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv1074488942 .yiv1074488942green {
color:#628c2a;}
#yiv1074488942 .yiv1074488942MsoNormal {
margin:0 0 0 0;}
#yiv1074488942 o {
font-size:0;}
#yiv1074488942 #yiv1074488942photos div {
float:left;width:72px;}
#yiv1074488942 #yiv1074488942photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv1074488942 #yiv1074488942photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv1074488942 #yiv1074488942reco-category {
font-size:77%;}
#yiv1074488942 #yiv1074488942reco-desc {
font-size:77%;}
#yiv1074488942 .yiv1074488942replbq {
margin:4px;}
#yiv1074488942 #yiv1074488942ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg select,
#yiv1074488942 input, #yiv1074488942 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg pre, #yiv1074488942
code {
font:115% monospace;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg * {
line-height:1.22em;}
#yiv1074488942 #yiv1074488942ygrp-mlmsg #yiv1074488942logo {
padding-bottom:10px;}
#yiv1074488942 #yiv1074488942ygrp-msg p a {
font-family:Verdana;}
#yiv1074488942 #yiv1074488942ygrp-msg
p#yiv1074488942attach-count span {
color:#1E66AE;font-weight:700;}
#yiv1074488942 #yiv1074488942ygrp-reco
#yiv1074488942reco-head {
color:#ff7900;font-weight:700;}
#yiv1074488942 #yiv1074488942ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv1074488942 #yiv1074488942ygrp-sponsor #yiv1074488942ov
li a {
font-size:130%;text-decoration:none;}
#yiv1074488942 #yiv1074488942ygrp-sponsor #yiv1074488942ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv1074488942 #yiv1074488942ygrp-sponsor #yiv1074488942ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv1074488942 #yiv1074488942ygrp-text {
font-family:Georgia;}
#yiv1074488942 #yiv1074488942ygrp-text p {
margin:0 0 1em 0;}
#yiv1074488942 #yiv1074488942ygrp-text tt {
font-size:120%;}
#yiv1074488942 #yiv1074488942ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv1074488942
|
?
The troubleshooting flowchart on the manual says to replace two gallium transistors on that board.
I tried the whack test. Nothing.
I'm just thinking that maybe I don't have the settings right on the unit, because I'd feel really dumb to put work into replacing a board only to find I didn't have a switch turned on or a knob in the right setting.
Andrew
Hey Andrew,
I don't know anything about your specific scope. However, while this is a Tektronix document <> it has good general advice on how to troubleshoot any analog scope. The older versions of XYZs of Oscilloscopes <> are also very appropriate for learning about the general workings of scopes of this vintage.
Siggi?
|
What test gear do you have? That will help people advise you. Did it come with a probe?
The manual suggests approaches appropriate to a commercial environment where labor is expensive and parts are readily obtained. In your case labor is actually what you're after. Except you'll call it "experience" after you're done. Being able to say you have repaired a 100 MHz analog scope is non-trivial. That's a good scope, though old age will make it a bit cranky. It will serve you well even when you get newer gear.
You can make a limited test of the transistors by measuring the forward resistance of the B-E and B-C junctions with an ohmmeter. The B-C resistance will be smaller than the B-E resistance because the larger area of the collector trumps the higher doping level of the emitter. Use the highest resistance ranges. You may encounter problems with DMMs that don't supply sufficient voltage to turn on the transistor. I learned this trick using an analog VOM. It doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that they give away, measure hFE with it. That should suffice for testing the two transistors, But beware of the crappy transistor sockets, You should probably solder some leads with grabbers or alligator clips. I just tried two red ones. One worked, the other didn't, but both were intermittent. An old yellow HF DMM had a better socket and worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing. Make sure you know where the high voltages are and stay away from them. I've heard it's rather painful at best and lethal at worst. If you do need to work near it, keep your left hand in your pocket and wear rubber sole shoes. HF nitrile gloves might not be a bad idea, though I don't know how good they'd be. Not quite sure what is recommended for southpaws. Be aware that the HV capacitors and the CRT can hold a charge for quite a while. Before you EVER touch anything in the HV section, ground it with a screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over a week to fix the horizontal section in my Dumont working a couple of hours each evening.
Most important....
Have Fun!
Reg
|
I have a fluke digital multimeter, a weller soldering station, and not much else. I'm slowly building up what I can when I have a specific need or find a good deal.
I bought a set of probes for it off ebay
There's no rush for me to fix it, so I can take the next 10 years if need be. Should I de-solder the transistors for testing?
I heard that with very high voltages, the thickness of the gloves are what's important. That's why lineman's gloves and spark plug boots are so thick.
I have a thick pair of rubber gloves that I'll probably be wearing for safety after leaving it unplugged for a while.
I also need to make a high resistance capacitor discharge tool. I believe I have some high capacity resistors I've salvaged from some equipment.
Thanks for the tips. Any further help is appreciated.
Andrew
--------------------------------------------
toggle quoted message
Show quoted text
On Sun, 10/8/17, Reginald Beardsley pulaskite@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 11:30 AM
?
What test gear do you have? That will help people
advise you. Did it come with a probe?
The manual suggests approaches appropriate to a commercial
environment where labor is expensive and parts are readily
obtained. In your case labor is actually what you're
after. Except you'll call it "experience"
after you're done. Being able to say you have repaired
a 100 MHz analog scope is non-trivial. That's a good
scope, though old age will make it a bit cranky. It will
serve you well even when you get newer gear.
You can make a limited test of the transistors by measuring
the forward resistance of the B-E and B-C junctions with an
ohmmeter. The B-C resistance will be smaller than the B-E
resistance because the larger area of the collector trumps
the higher doping level of the emitter. Use the highest
resistance ranges. You may encounter problems with DMMs
that don't supply sufficient voltage to turn on the
transistor. I learned this trick using an analog VOM. It
doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that they
give away, measure hFE with it. That should suffice for
testing the two transistors, But beware of the crappy
transistor sockets, You should probably solder some leads
with grabbers or alligator clips. I just tried two red
ones. One worked, the other didn't, but both were
intermittent. An old yellow HF DMM had a better socket and
worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing. Make
sure you know where the high voltages are and stay away from
them. I've heard it's rather painful at best and
lethal at worst. If you do need to work near it, keep your
left hand in your pocket and wear rubber sole shoes. HF
nitrile gloves might not be a bad idea, though I don't
know how good they'd be. Not quite sure what is
recommended for southpaws. Be aware that the HV capacitors
and the CRT can hold a charge for quite a while. Before you
EVER touch anything in the HV section, ground it with a
screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over a
week to fix the horizontal section in my Dumont working a
couple of hours each evening.
Most important....
Have Fun!
Reg
#yiv4333658034 #yiv4333658034 --
#yiv4333658034ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034ads {
margin-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad {
padding:0 0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad p {
margin:0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad a {
color:#0000ff;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc {
font-family:Arial;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc #yiv4333658034hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc .yiv4333658034ad {
margin-bottom:10px;padding:0 0;}
#yiv4333658034 #yiv4333658034actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4333658034 #yiv4333658034activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4333658034 #yiv4333658034activity span {
font-weight:700;}
#yiv4333658034 #yiv4333658034activity span:first-child {
text-transform:uppercase;}
#yiv4333658034 #yiv4333658034activity span a {
color:#5085b6;text-decoration:none;}
#yiv4333658034 #yiv4333658034activity span span {
color:#ff7900;}
#yiv4333658034 #yiv4333658034activity span
.yiv4333658034underline {
text-decoration:underline;}
#yiv4333658034 .yiv4333658034attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4333658034 .yiv4333658034attach div a {
text-decoration:none;}
#yiv4333658034 .yiv4333658034attach img {
border:none;padding-right:5px;}
#yiv4333658034 .yiv4333658034attach label {
display:block;margin-bottom:5px;}
#yiv4333658034 .yiv4333658034attach label a {
text-decoration:none;}
#yiv4333658034 blockquote {
margin:0 0 0 4px;}
#yiv4333658034 .yiv4333658034bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4333658034 .yiv4333658034bold a {
text-decoration:none;}
#yiv4333658034 dd.yiv4333658034last p a {
font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p
span.yiv4333658034yshortcuts {
margin-right:0;}
#yiv4333658034 div.yiv4333658034attach-table div div a {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034attach-table {
width:400px;}
#yiv4333658034 div.yiv4333658034file-title a, #yiv4333658034
div.yiv4333658034file-title a:active, #yiv4333658034
div.yiv4333658034file-title a:hover, #yiv4333658034
div.yiv4333658034file-title a:visited {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034photo-title a,
#yiv4333658034 div.yiv4333658034photo-title a:active,
#yiv4333658034 div.yiv4333658034photo-title a:hover,
#yiv4333658034 div.yiv4333658034photo-title a:visited {
text-decoration:none;}
#yiv4333658034 div#yiv4333658034ygrp-mlmsg
#yiv4333658034ygrp-msg p a span.yiv4333658034yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4333658034 .yiv4333658034green {
color:#628c2a;}
#yiv4333658034 .yiv4333658034MsoNormal {
margin:0 0 0 0;}
#yiv4333658034 o {
font-size:0;}
#yiv4333658034 #yiv4333658034photos div {
float:left;width:72px;}
#yiv4333658034 #yiv4333658034photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4333658034 #yiv4333658034photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4333658034 #yiv4333658034reco-category {
font-size:77%;}
#yiv4333658034 #yiv4333658034reco-desc {
font-size:77%;}
#yiv4333658034 .yiv4333658034replbq {
margin:4px;}
#yiv4333658034 #yiv4333658034ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg select,
#yiv4333658034 input, #yiv4333658034 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg pre, #yiv4333658034
code {
font:115% monospace;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg * {
line-height:1.22em;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg #yiv4333658034logo {
padding-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-msg p a {
font-family:Verdana;}
#yiv4333658034 #yiv4333658034ygrp-msg
p#yiv4333658034attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco
#yiv4333658034reco-head {
color:#ff7900;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
li a {
font-size:130%;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4333658034 #yiv4333658034ygrp-text {
font-family:Georgia;}
#yiv4333658034 #yiv4333658034ygrp-text p {
margin:0 0 1em 0;}
#yiv4333658034 #yiv4333658034ygrp-text tt {
font-size:120%;}
#yiv4333658034 #yiv4333658034ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv4333658034
|
The resistors in the deflection amplifier output stages (in this case the horizontal deflection amplifier) have an annoying tendency to drift much higher in value and eventually fail open. This is also an issue with the HP853A, I have repaired three or four of these with essentially the same failure. You can check the resistors easily with an ohmmeter - if you measure higher resistance than the value shown in the schematic, then the resistor has failed. Suitable replacements are available from DigiKey or Mouser at low cost. If you find a failed resistor of a specific type, then change all of the resistors of that type in the deflection amplifier output stage (even the "good" ones). I have repaired at least one unit where all of the deflection amplifier output stage resistors were open-circuit on both the horizontal and vertical amplifiers.
|
Hi re fixing 180 from memory
Before removing the transistors a simple
test
Have you tested all the power supply rails
on the pcb for the main frame for this test I would remove the plugging just in
case they are causing any problems ?
?
Display switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier into external with the intensity
turned up you should have a spot
turning the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one down magnifier
should be set to 1 )
now connect a signal into the external ?BNC
input below ?I just held a length of wire and put into the bnc socket ?you
should see a horizontal line if not it is probably the drive transistors
if you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots one on left one
on right if one hasten moved then it is that pare of transistors that has a
fault
?
this was my first HP scope to repair ?Paul
B
From:
hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]
Sent: 08 October 2017 18:02
To: hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
?
?
I have a fluke digital multimeter, a weller soldering
station, and not much else. I'm slowly building up what I can when I have a
specific need or find a good deal.
I bought a set of probes for it off ebay
http://www.ebay.com/itm/P6100-2PCS-Oscilloscope-Probe-Kit-100-MHz-Clip-Test-Probe-For-Tektronix-HP-Rigol/322409718031?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
There's no rush for me to fix it, so I can take the next 10 years if need be. Should
I de-solder the transistors for testing?
I heard that with very high voltages, the thickness of the gloves are what's
important. That's why lineman's gloves and spark plug boots are so thick.
I have a thick pair of rubber gloves that I'll probably be wearing for safety
after leaving it unplugged for a while.
I also need to make a high resistance capacitor discharge tool. I believe I
have some high capacity resistors I've salvaged from some equipment.
Thanks for the tips. Any further help is appreciated.
Andrew
--------------------------------------------
On Sun, 10/8/17, Reginald Beardsley pulaskite@... [hp_agilent_equipment]
<hp_agilent_equipment@...>
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 11:30 AM
?
What test gear do you have? That will help people
advise you. Did it come with a probe?
The manual suggests approaches appropriate to a commercial
environment where labor is expensive and parts are readily
obtained. In your case labor is actually what you're
after. Except you'll call it "experience"
after you're done. Being able to say you have repaired
a 100 MHz analog scope is non-trivial. That's a good
scope, though old age will make it a bit cranky. It will
serve you well even when you get newer gear.
You can make a limited test of the transistors by measuring
the forward resistance of the B-E and B-C junctions with an
ohmmeter. The B-C resistance will be smaller than the B-E
resistance because the larger area of the collector trumps
the higher doping level of the emitter. Use the highest
resistance ranges. You may encounter problems with DMMs
that don't supply sufficient voltage to turn on the
transistor. I learned this trick using an analog VOM. It
doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that they
give away, measure hFE with it. That should suffice for
testing the two transistors, But beware of the crappy
transistor sockets, You should probably solder some leads
with grabbers or alligator clips. I just tried two red
ones. One worked, the other didn't, but both were
intermittent. An old yellow HF DMM had a better socket and
worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing. Make
sure you know where the high voltages are and stay away from
them. I've heard it's rather painful at best and
lethal at worst. If you do need to work near it, keep your
left hand in your pocket and wear rubber sole shoes. HF
nitrile gloves might not be a bad idea, though I don't
know how good they'd be. Not quite sure what is
recommended for southpaws. Be aware that the HV capacitors
and the CRT can hold a charge for quite a while. Before you
EVER touch anything in the HV section, ground it with a
screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over a
week to fix the horizontal section in my Dumont
working a
couple of hours each evening.
Most important....
Have Fun!
Reg
#yiv4333658034 #yiv4333658034 --
#yiv4333658034ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034ads {
margin-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad {
padding:0 0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad p {
margin:0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad a {
color:#0000ff;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc {
font-family:Arial;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc #yiv4333658034hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc .yiv4333658034ad {
margin-bottom:10px;padding:0 0;}
#yiv4333658034 #yiv4333658034actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4333658034 #yiv4333658034activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4333658034 #yiv4333658034activity span {
font-weight:700;}
#yiv4333658034 #yiv4333658034activity span:first-child {
text-transform:uppercase;}
#yiv4333658034 #yiv4333658034activity span a {
color:#5085b6;text-decoration:none;}
#yiv4333658034 #yiv4333658034activity span span {
color:#ff7900;}
#yiv4333658034 #yiv4333658034activity span
.yiv4333658034underline {
text-decoration:underline;}
#yiv4333658034 .yiv4333658034attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4333658034 .yiv4333658034attach div a {
text-decoration:none;}
#yiv4333658034 .yiv4333658034attach img {
border:none;padding-right:5px;}
#yiv4333658034 .yiv4333658034attach label {
display:block;margin-bottom:5px;}
#yiv4333658034 .yiv4333658034attach label a {
text-decoration:none;}
#yiv4333658034 blockquote {
margin:0 0 0 4px;}
#yiv4333658034 .yiv4333658034bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4333658034 .yiv4333658034bold a {
text-decoration:none;}
#yiv4333658034 dd.yiv4333658034last p a {
font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p
span.yiv4333658034yshortcuts {
margin-right:0;}
#yiv4333658034 div.yiv4333658034attach-table div div a {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034attach-table {
width:400px;}
#yiv4333658034 div.yiv4333658034file-title a, #yiv4333658034
div.yiv4333658034file-title a:active, #yiv4333658034
div.yiv4333658034file-title a:hover, #yiv4333658034
div.yiv4333658034file-title a:visited {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034photo-title a,
#yiv4333658034 div.yiv4333658034photo-title a:active,
#yiv4333658034 div.yiv4333658034photo-title a:hover,
#yiv4333658034 div.yiv4333658034photo-title a:visited {
text-decoration:none;}
#yiv4333658034 div#yiv4333658034ygrp-mlmsg
#yiv4333658034ygrp-msg p a span.yiv4333658034yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4333658034 .yiv4333658034green {
color:#628c2a;}
#yiv4333658034 .yiv4333658034MsoNormal {
margin:0 0 0 0;}
#yiv4333658034 o {
font-size:0;}
#yiv4333658034 #yiv4333658034photos div {
float:left;width:72px;}
#yiv4333658034 #yiv4333658034photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4333658034 #yiv4333658034photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4333658034 #yiv4333658034reco-category {
font-size:77%;}
#yiv4333658034 #yiv4333658034reco-desc {
font-size:77%;}
#yiv4333658034 .yiv4333658034replbq {
margin:4px;}
#yiv4333658034 #yiv4333658034ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg select,
#yiv4333658034 input, #yiv4333658034 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg pre, #yiv4333658034
code {
font:115% monospace;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg * {
line-height:1.22em;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg #yiv4333658034logo {
padding-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-msg p a {
font-family:Verdana;}
#yiv4333658034 #yiv4333658034ygrp-msg
p#yiv4333658034attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco
#yiv4333658034reco-head {
color:#ff7900;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
li a {
font-size:130%;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4333658034 #yiv4333658034ygrp-sponsor #yiv4333658034ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4333658034 #yiv4333658034ygrp-text {
font-family:Georgia;}
#yiv4333658034 #yiv4333658034ygrp-text p {
margin:0 0 1em 0;}
#yiv4333658034 #yiv4333658034ygrp-text tt {
font-size:120%;}
#yiv4333658034 #yiv4333658034ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv4333658034
No virus found in this message.
Checked by AVG -
Version: 2016.0.8013 / Virus Database: 4782/15018 - Release Date: 10/08/17
|
Andrew,
Give it a few days for other people to check in before you DO anything. There are some VERY knowledgeable people on this list who know far more than I do. Spend your spare time studying the schematic for the horizontal section and where things are on the board. And most importantly, what the voltage levels are at various points with particular attention to anything over 50 V. Then start with the easy stuff and keep going until you find the actual problem. Trouble shooting is an art. The thought process is the same no matter what the particular technology or context. It's a very valuable skill.
I tossed in the bit about rubber gloves without any factual basis. Probably a bad idea as it might give a false sense of security. I never wear gloves for anything if it's reasonable. So for HV I just made damn sure I knew what not to touch. Insulation is a function of both material and thickness. So there is no blanket answer and HV gets weirder the higher you go. But I'm old enough that to remember when everything I saw had tubes and there was a self service tester at the drugstore. I also blew up an AC/DC tube radio by connecting a ground when I was about 12. It *really* helped me get those late night long distance AM broadcast band stations. After I got a new radio. :-)
HF ads have coupons for free screwdrivers, DMMs and other stuff. Keep an eye out for them. A complete crap screwdriver with a resistor and alligator clip will do just fine for discharging caps. There's no harm in just using a junk screwdriver without the resistor. Unless, of course, you melt a push on terminal so the lead won't fit, Then you have something else to fix with a file. You can avoid that by making contact with the potential HV source first so that the arc is to ground. And lots of people have habitually used their good screwdrivers by making sure the arc was not at the tip where it could cause damage.
If your Fluke doesn't have an hFE test, the HF DMM suitably modified will do nicely for basic transistor function tests. I've got a better meter, though it's not a Fluke. But most of the time I use the HF units. I've got lots of them and often not interested in getting an accurate answer. I don't care if the meter says 110 V or 115 V. All I care about is that there is line voltage present at that point.
Have Fun!
Reg
|
Thanks for the help. What can I use for a signal? I don't have a signal generator. I tried testing it with a 3v 800ma wall wart using the EXT INPUT and didn't get a dot or anything.
I tried using a 1.5v battery on the lower left input probe and, while holding the test button down I could see the dot jump up and down 1.5 square up each time I contacted the battery terminal. I can't get a dot to appear without holding the test button, so I feel like the knobs and switches probably aren't adjusted correctly.
It worked the same way with the lower left INPUT when I tried the wall wart. The dot jumped up 3 squares, but only when holding the test beam button.
Do you think I'm doing the test correctly, or are there other switches and knobs I need to try different settings with?
Thank again!
Andrew
--------------------------------------------
toggle quoted message
Show quoted text
On Sun, 10/8/17, 'Paul Bicknell' paul@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 1:05 PM
?
Hi re
fixing 180 from memory
Before
removing the transistors a simple
test
Have
you tested all the power supply rails
on the pcb for the main frame for this test I would remove
the plugging just in
case they are causing any problems ?
?
Display
switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier into
external with the intensity
turned up you should have a spot
turning
the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one
down magnifier
should be set to 1 )
now
connect a signal into the external ?BNC
input below ?I just held a length of wire and put into the
bnc socket ?you
should see a horizontal line if not it is probably the drive
transistors
if
you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots
one on left one
on right if one hasten moved then it is that pare of
transistors that has a
fault
?
this
was my first HP scope to repair ?Paul
B
From:
hp_agilent_equipment@...
[mailto: hp_agilent_equipment@... ]
Sent: 08
October 2017 18:02
To:
hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs
repair ( San Antonio TX )
?
?
I have a fluke
digital multimeter, a weller soldering
station, and not much else. I'm slowly building up what
I can when I have a
specific need or find a good deal.
I bought a set of probes for it off ebay
There's no rush for me to fix it, so I can take the next
10 years if need be. Should
I de-solder the transistors for testing?
I heard that with very high voltages, the thickness of the
gloves are what's
important. That's why lineman's gloves and spark
plug boots are so thick.
I have a thick pair of rubber gloves that I'll probably
be wearing for safety
after leaving it unplugged for a while.
I also need to make a high resistance capacitor discharge
tool. I believe I
have some high capacity resistors I've salvaged from
some equipment.
Thanks for the tips. Any further help is appreciated.
Andrew
--------------------------------------------
On Sun, 10/8/17, Reginald Beardsley pulaskite@...
[hp_agilent_equipment]
< hp_agilent_equipment@... >
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A
Oscilliscope needs repair ( San Antonio TX )
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 11:30 AM
?
What test gear do you have? That will help people
advise you. Did it come with a probe?
The manual suggests approaches appropriate to a
commercial
environment where labor is expensive and parts are
readily
obtained. In your case labor is actually what you're
after. Except you'll call it "experience"
after you're done. Being able to say you have
repaired
a 100 MHz analog scope is non-trivial. That's a good
scope, though old age will make it a bit cranky. It will
serve you well even when you get newer gear.
You can make a limited test of the transistors by
measuring
the forward resistance of the B-E and B-C junctions with
an
ohmmeter. The B-C resistance will be smaller than the B-E
resistance because the larger area of the collector
trumps
the higher doping level of the emitter. Use the highest
resistance ranges. You may encounter problems with DMMs
that don't supply sufficient voltage to turn on the
transistor. I learned this trick using an analog VOM. It
doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that
they
give away, measure hFE with it. That should suffice for
testing the two transistors, But beware of the crappy
transistor sockets, You should probably solder some leads
with grabbers or alligator clips. I just tried two red
ones. One worked, the other didn't, but both were
intermittent. An old yellow HF DMM had a better socket
and
worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing.
Make
sure you know where the high voltages are and stay away
from
them. I've heard it's rather painful at best and
lethal at worst. If you do need to work near it, keep
your
left hand in your pocket and wear rubber sole shoes. HF
nitrile gloves might not be a bad idea, though I
don't
know how good they'd be. Not quite sure what is
recommended for southpaws. Be aware that the HV
capacitors
and the CRT can hold a charge for quite a while. Before
you
EVER touch anything in the HV section, ground it with a
screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over
a
week to fix the horizontal section in my Dumont
working a
couple of hours each evening.
Most important....
Have Fun!
Reg
#yiv4333658034 #yiv4333658034 --
#yiv4333658034ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034ads {
margin-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad {
padding:0 0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad p
{
margin:0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad a
{
color:#0000ff;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc {
font-family:Arial;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc #yiv4333658034hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc .yiv4333658034ad {
margin-bottom:10px;padding:0 0;}
#yiv4333658034 #yiv4333658034actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4333658034 #yiv4333658034activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4333658034 #yiv4333658034activity span {
font-weight:700;}
#yiv4333658034 #yiv4333658034activity span:first-child {
text-transform:uppercase;}
#yiv4333658034 #yiv4333658034activity span a {
color:#5085b6;text-decoration:none;}
#yiv4333658034 #yiv4333658034activity span span {
color:#ff7900;}
#yiv4333658034 #yiv4333658034activity span
.yiv4333658034underline {
text-decoration:underline;}
#yiv4333658034 .yiv4333658034attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4333658034 .yiv4333658034attach div a {
text-decoration:none;}
#yiv4333658034 .yiv4333658034attach img {
border:none;padding-right:5px;}
#yiv4333658034 .yiv4333658034attach label {
display:block;margin-bottom:5px;}
#yiv4333658034 .yiv4333658034attach label a {
text-decoration:none;}
#yiv4333658034 blockquote {
margin:0 0 0 4px;}
#yiv4333658034 .yiv4333658034bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4333658034 .yiv4333658034bold a {
text-decoration:none;}
#yiv4333658034 dd.yiv4333658034last p a {
font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p
span.yiv4333658034yshortcuts {
margin-right:0;}
#yiv4333658034 div.yiv4333658034attach-table div div a {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034attach-table {
width:400px;}
#yiv4333658034 div.yiv4333658034file-title a,
#yiv4333658034
div.yiv4333658034file-title a:active, #yiv4333658034
div.yiv4333658034file-title a:hover, #yiv4333658034
div.yiv4333658034file-title a:visited {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034photo-title a,
#yiv4333658034 div.yiv4333658034photo-title a:active,
#yiv4333658034 div.yiv4333658034photo-title a:hover,
#yiv4333658034 div.yiv4333658034photo-title a:visited {
text-decoration:none;}
#yiv4333658034 div#yiv4333658034ygrp-mlmsg
#yiv4333658034ygrp-msg p a span.yiv4333658034yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4333658034 .yiv4333658034green {
color:#628c2a;}
#yiv4333658034 .yiv4333658034MsoNormal {
margin:0 0 0 0;}
#yiv4333658034 o {
font-size:0;}
#yiv4333658034 #yiv4333658034photos div {
float:left;width:72px;}
#yiv4333658034 #yiv4333658034photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4333658034 #yiv4333658034photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4333658034 #yiv4333658034reco-category {
font-size:77%;}
#yiv4333658034 #yiv4333658034reco-desc {
font-size:77%;}
#yiv4333658034 .yiv4333658034replbq {
margin:4px;}
#yiv4333658034 #yiv4333658034ygrp-actbar div a:first-child
{
margin-right:2px;padding-right:5px;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg select,
#yiv4333658034 input, #yiv4333658034 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg pre,
#yiv4333658034
code {
font:115% monospace;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg * {
line-height:1.22em;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg #yiv4333658034logo
{
padding-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-msg p a {
font-family:Verdana;}
#yiv4333658034 #yiv4333658034ygrp-msg
p#yiv4333658034attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco
#yiv4333658034reco-head {
color:#ff7900;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li a {
font-size:130%;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4333658034 #yiv4333658034ygrp-text {
font-family: Georgia ;}
#yiv4333658034 #yiv4333658034ygrp-text p {
margin:0 0 1em 0;}
#yiv4333658034 #yiv4333658034ygrp-text tt {
font-size:120%;}
#yiv4333658034 #yiv4333658034ygrp-vital ul li:last-child
{
border-right:none !important;
}
#yiv4333658034
No virus found in this
message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15018 - Release
Date: 10/08/17
#yiv7282166702 #yiv7282166702 --
#yiv7282166702ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702ads {
margin-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad {
padding:0 0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad p {
margin:0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad a {
color:#0000ff;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc {
font-family:Arial;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc #yiv7282166702hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc .yiv7282166702ad {
margin-bottom:10px;padding:0 0;}
#yiv7282166702 #yiv7282166702actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv7282166702 #yiv7282166702activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv7282166702 #yiv7282166702activity span {
font-weight:700;}
#yiv7282166702 #yiv7282166702activity span:first-child {
text-transform:uppercase;}
#yiv7282166702 #yiv7282166702activity span a {
color:#5085b6;text-decoration:none;}
#yiv7282166702 #yiv7282166702activity span span {
color:#ff7900;}
#yiv7282166702 #yiv7282166702activity span
.yiv7282166702underline {
text-decoration:underline;}
#yiv7282166702 .yiv7282166702attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv7282166702 .yiv7282166702attach div a {
text-decoration:none;}
#yiv7282166702 .yiv7282166702attach img {
border:none;padding-right:5px;}
#yiv7282166702 .yiv7282166702attach label {
display:block;margin-bottom:5px;}
#yiv7282166702 .yiv7282166702attach label a {
text-decoration:none;}
#yiv7282166702 blockquote {
margin:0 0 0 4px;}
#yiv7282166702 .yiv7282166702bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv7282166702 .yiv7282166702bold a {
text-decoration:none;}
#yiv7282166702 dd.yiv7282166702last p a {
font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p
span.yiv7282166702yshortcuts {
margin-right:0;}
#yiv7282166702 div.yiv7282166702attach-table div div a {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702attach-table {
width:400px;}
#yiv7282166702 div.yiv7282166702file-title a, #yiv7282166702
div.yiv7282166702file-title a:active, #yiv7282166702
div.yiv7282166702file-title a:hover, #yiv7282166702
div.yiv7282166702file-title a:visited {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702photo-title a,
#yiv7282166702 div.yiv7282166702photo-title a:active,
#yiv7282166702 div.yiv7282166702photo-title a:hover,
#yiv7282166702 div.yiv7282166702photo-title a:visited {
text-decoration:none;}
#yiv7282166702 div#yiv7282166702ygrp-mlmsg
#yiv7282166702ygrp-msg p a span.yiv7282166702yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv7282166702 .yiv7282166702green {
color:#628c2a;}
#yiv7282166702 .yiv7282166702MsoNormal {
margin:0 0 0 0;}
#yiv7282166702 o {
font-size:0;}
#yiv7282166702 #yiv7282166702photos div {
float:left;width:72px;}
#yiv7282166702 #yiv7282166702photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv7282166702 #yiv7282166702photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv7282166702 #yiv7282166702reco-category {
font-size:77%;}
#yiv7282166702 #yiv7282166702reco-desc {
font-size:77%;}
#yiv7282166702 .yiv7282166702replbq {
margin:4px;}
#yiv7282166702 #yiv7282166702ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg select,
#yiv7282166702 input, #yiv7282166702 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg pre, #yiv7282166702
code {
font:115% monospace;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg * {
line-height:1.22em;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg #yiv7282166702logo {
padding-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-msg p a {
font-family:Verdana;}
#yiv7282166702 #yiv7282166702ygrp-msg
p#yiv7282166702attach-count span {
color:#1E66AE;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco
#yiv7282166702reco-head {
color:#ff7900;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
li a {
font-size:130%;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv7282166702 #yiv7282166702ygrp-text {
font-family:Georgia;}
#yiv7282166702 #yiv7282166702ygrp-text p {
margin:0 0 1em 0;}
#yiv7282166702 #yiv7282166702ygrp-text tt {
font-size:120%;}
#yiv7282166702 #yiv7282166702ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv7282166702
|
Cool. Thank you for the tip on where to check.
I'm still trying to figure out if there are any settings I need to try without cracking the case open. I'll save this email for reference when I open it up.
Andrew
--------------------------------------------
toggle quoted message
Show quoted text
On Sun, 10/8/17, knener@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 12:44 PM
?
The resistors in the deflection amplifier output
stages (in this case the horizontal deflection amplifier)
have an annoying tendency to drift much higher in value and
eventually fail open. This is also an issue with the HP853A,
I have repaired three or four of these with essentially the
same failure. You can check the resistors easily with an
ohmmeter - if you measure higher resistance than the value
shown in the schematic, then the resistor has failed.
Suitable replacements are available from DigiKey or Mouser
at low cost. If you find a failed resistor of a specific
type, then change all of the resistors of that type in the
deflection amplifier output stage (even the "good"
ones). I have repaired at least one unit where all of the
deflection amplifier output stage resistors were
open-circuit on both the horizontal and vertical
amplifiers.
#yiv0798676708 #yiv0798676708 --
#yiv0798676708ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv0798676708 #yiv0798676708ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv0798676708 #yiv0798676708ygrp-mkp #yiv0798676708hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv0798676708 #yiv0798676708ygrp-mkp #yiv0798676708ads {
margin-bottom:10px;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad {
padding:0 0;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad p {
margin:0;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad a {
color:#0000ff;text-decoration:none;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc {
font-family:Arial;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc #yiv0798676708hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc .yiv0798676708ad {
margin-bottom:10px;padding:0 0;}
#yiv0798676708 #yiv0798676708actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv0798676708 #yiv0798676708activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv0798676708 #yiv0798676708activity span {
font-weight:700;}
#yiv0798676708 #yiv0798676708activity span:first-child {
text-transform:uppercase;}
#yiv0798676708 #yiv0798676708activity span a {
color:#5085b6;text-decoration:none;}
#yiv0798676708 #yiv0798676708activity span span {
color:#ff7900;}
#yiv0798676708 #yiv0798676708activity span
.yiv0798676708underline {
text-decoration:underline;}
#yiv0798676708 .yiv0798676708attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv0798676708 .yiv0798676708attach div a {
text-decoration:none;}
#yiv0798676708 .yiv0798676708attach img {
border:none;padding-right:5px;}
#yiv0798676708 .yiv0798676708attach label {
display:block;margin-bottom:5px;}
#yiv0798676708 .yiv0798676708attach label a {
text-decoration:none;}
#yiv0798676708 blockquote {
margin:0 0 0 4px;}
#yiv0798676708 .yiv0798676708bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv0798676708 .yiv0798676708bold a {
text-decoration:none;}
#yiv0798676708 dd.yiv0798676708last p a {
font-family:Verdana;font-weight:700;}
#yiv0798676708 dd.yiv0798676708last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv0798676708 dd.yiv0798676708last p
span.yiv0798676708yshortcuts {
margin-right:0;}
#yiv0798676708 div.yiv0798676708attach-table div div a {
text-decoration:none;}
#yiv0798676708 div.yiv0798676708attach-table {
width:400px;}
#yiv0798676708 div.yiv0798676708file-title a, #yiv0798676708
div.yiv0798676708file-title a:active, #yiv0798676708
div.yiv0798676708file-title a:hover, #yiv0798676708
div.yiv0798676708file-title a:visited {
text-decoration:none;}
#yiv0798676708 div.yiv0798676708photo-title a,
#yiv0798676708 div.yiv0798676708photo-title a:active,
#yiv0798676708 div.yiv0798676708photo-title a:hover,
#yiv0798676708 div.yiv0798676708photo-title a:visited {
text-decoration:none;}
#yiv0798676708 div#yiv0798676708ygrp-mlmsg
#yiv0798676708ygrp-msg p a span.yiv0798676708yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv0798676708 .yiv0798676708green {
color:#628c2a;}
#yiv0798676708 .yiv0798676708MsoNormal {
margin:0 0 0 0;}
#yiv0798676708 o {
font-size:0;}
#yiv0798676708 #yiv0798676708photos div {
float:left;width:72px;}
#yiv0798676708 #yiv0798676708photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv0798676708 #yiv0798676708photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv0798676708 #yiv0798676708reco-category {
font-size:77%;}
#yiv0798676708 #yiv0798676708reco-desc {
font-size:77%;}
#yiv0798676708 .yiv0798676708replbq {
margin:4px;}
#yiv0798676708 #yiv0798676708ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg select,
#yiv0798676708 input, #yiv0798676708 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg pre, #yiv0798676708
code {
font:115% monospace;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg * {
line-height:1.22em;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg #yiv0798676708logo {
padding-bottom:10px;}
#yiv0798676708 #yiv0798676708ygrp-msg p a {
font-family:Verdana;}
#yiv0798676708 #yiv0798676708ygrp-msg
p#yiv0798676708attach-count span {
color:#1E66AE;font-weight:700;}
#yiv0798676708 #yiv0798676708ygrp-reco
#yiv0798676708reco-head {
color:#ff7900;font-weight:700;}
#yiv0798676708 #yiv0798676708ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv0798676708 #yiv0798676708ygrp-sponsor #yiv0798676708ov
li a {
font-size:130%;text-decoration:none;}
#yiv0798676708 #yiv0798676708ygrp-sponsor #yiv0798676708ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv0798676708 #yiv0798676708ygrp-sponsor #yiv0798676708ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv0798676708 #yiv0798676708ygrp-text {
font-family:Georgia;}
#yiv0798676708 #yiv0798676708ygrp-text p {
margin:0 0 1em 0;}
#yiv0798676708 #yiv0798676708ygrp-text tt {
font-size:120%;}
#yiv0798676708 #yiv0798676708ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv0798676708
|
One last question for the night. Is there a component failure that would cause the beam/dot not to show on the screen when I apply low voltage to the test leads (1.5v battery) I have to hold the TEST button to find the FIND BEAM button to see anything other than the backlight, and I wish I had 3 hands, but this shouldn't be necessary.
It might just be a switch or knob that I haven't adjusted correctly, so I'm trying to set it up correctly for testing in order to figure out if there is anything malfunctioning.
Best Regards,
Andrew
--------------------------------------------
toggle quoted message
Show quoted text
On Tue, 10/10/17, Andrew Maich andremajic@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Tuesday, October 10, 2017, 8:15 PM
?
Cool. Thank you for the tip on where to check.
I'm still trying to figure out if there are any settings
I need to try without cracking the case open. I'll save
this email for reference when I open it up.
Andrew
--------------------------------------------
On Sun, 10/8/17, knener@... [hp_agilent_equipment]
<hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A
Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 12:44 PM
?
The resistors in the deflection amplifier output
stages (in this case the horizontal deflection
amplifier)
have an annoying tendency to drift much higher in value
and
eventually fail open. This is also an issue with the
HP853A,
I have repaired three or four of these with essentially
the
same failure. You can check the resistors easily with an
ohmmeter - if you measure higher resistance than the
value
shown in the schematic, then the resistor has failed.
Suitable replacements are available from DigiKey or
Mouser
at low cost. If you find a failed resistor of a specific
type, then change all of the resistors of that type in
the
deflection amplifier output stage (even the
"good"
ones). I have repaired at least one unit where all of
the
deflection amplifier output stage resistors were
open-circuit on both the horizontal and vertical
amplifiers.
#yiv0798676708 #yiv0798676708 --
#yiv0798676708ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv0798676708 #yiv0798676708ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv0798676708 #yiv0798676708ygrp-mkp #yiv0798676708hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv0798676708 #yiv0798676708ygrp-mkp #yiv0798676708ads
{
margin-bottom:10px;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad {
padding:0 0;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad p
{
margin:0;}
#yiv0798676708 #yiv0798676708ygrp-mkp .yiv0798676708ad a
{
color:#0000ff;text-decoration:none;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc {
font-family:Arial;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc #yiv0798676708hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ygrp-lc .yiv0798676708ad {
margin-bottom:10px;padding:0 0;}
#yiv0798676708 #yiv0798676708actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv0798676708 #yiv0798676708activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv0798676708 #yiv0798676708activity span {
font-weight:700;}
#yiv0798676708 #yiv0798676708activity span:first-child {
text-transform:uppercase;}
#yiv0798676708 #yiv0798676708activity span a {
color:#5085b6;text-decoration:none;}
#yiv0798676708 #yiv0798676708activity span span {
color:#ff7900;}
#yiv0798676708 #yiv0798676708activity span
.yiv0798676708underline {
text-decoration:underline;}
#yiv0798676708 .yiv0798676708attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv0798676708 .yiv0798676708attach div a {
text-decoration:none;}
#yiv0798676708 .yiv0798676708attach img {
border:none;padding-right:5px;}
#yiv0798676708 .yiv0798676708attach label {
display:block;margin-bottom:5px;}
#yiv0798676708 .yiv0798676708attach label a {
text-decoration:none;}
#yiv0798676708 blockquote {
margin:0 0 0 4px;}
#yiv0798676708 .yiv0798676708bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv0798676708 .yiv0798676708bold a {
text-decoration:none;}
#yiv0798676708 dd.yiv0798676708last p a {
font-family:Verdana;font-weight:700;}
#yiv0798676708 dd.yiv0798676708last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv0798676708 dd.yiv0798676708last p
span.yiv0798676708yshortcuts {
margin-right:0;}
#yiv0798676708 div.yiv0798676708attach-table div div a {
text-decoration:none;}
#yiv0798676708 div.yiv0798676708attach-table {
width:400px;}
#yiv0798676708 div.yiv0798676708file-title a,
#yiv0798676708
div.yiv0798676708file-title a:active, #yiv0798676708
div.yiv0798676708file-title a:hover, #yiv0798676708
div.yiv0798676708file-title a:visited {
text-decoration:none;}
#yiv0798676708 div.yiv0798676708photo-title a,
#yiv0798676708 div.yiv0798676708photo-title a:active,
#yiv0798676708 div.yiv0798676708photo-title a:hover,
#yiv0798676708 div.yiv0798676708photo-title a:visited {
text-decoration:none;}
#yiv0798676708 div#yiv0798676708ygrp-mlmsg
#yiv0798676708ygrp-msg p a span.yiv0798676708yshortcuts
{
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv0798676708 .yiv0798676708green {
color:#628c2a;}
#yiv0798676708 .yiv0798676708MsoNormal {
margin:0 0 0 0;}
#yiv0798676708 o {
font-size:0;}
#yiv0798676708 #yiv0798676708photos div {
float:left;width:72px;}
#yiv0798676708 #yiv0798676708photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv0798676708 #yiv0798676708photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv0798676708 #yiv0798676708reco-category {
font-size:77%;}
#yiv0798676708 #yiv0798676708reco-desc {
font-size:77%;}
#yiv0798676708 .yiv0798676708replbq {
margin:4px;}
#yiv0798676708 #yiv0798676708ygrp-actbar div a:first-child
{
margin-right:2px;padding-right:5px;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg select,
#yiv0798676708 input, #yiv0798676708 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg pre,
#yiv0798676708
code {
font:115% monospace;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg * {
line-height:1.22em;}
#yiv0798676708 #yiv0798676708ygrp-mlmsg #yiv0798676708logo
{
padding-bottom:10px;}
#yiv0798676708 #yiv0798676708ygrp-msg p a {
font-family:Verdana;}
#yiv0798676708 #yiv0798676708ygrp-msg
p#yiv0798676708attach-count span {
color:#1E66AE;font-weight:700;}
#yiv0798676708 #yiv0798676708ygrp-reco
#yiv0798676708reco-head {
color:#ff7900;font-weight:700;}
#yiv0798676708 #yiv0798676708ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ov
li a {
font-size:130%;text-decoration:none;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv0798676708 #yiv0798676708ygrp-sponsor
#yiv0798676708ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv0798676708 #yiv0798676708ygrp-text {
font-family:Georgia;}
#yiv0798676708 #yiv0798676708ygrp-text p {
margin:0 0 1em 0;}
#yiv0798676708 #yiv0798676708ygrp-text tt {
font-size:120%;}
#yiv0798676708 #yiv0798676708ygrp-vital ul li:last-child
{
border-right:none !important;
}
#yiv0798676708
#yiv4312101745 #yiv4312101745 --
#yiv4312101745ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4312101745 #yiv4312101745ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4312101745 #yiv4312101745ygrp-mkp #yiv4312101745hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4312101745 #yiv4312101745ygrp-mkp #yiv4312101745ads {
margin-bottom:10px;}
#yiv4312101745 #yiv4312101745ygrp-mkp .yiv4312101745ad {
padding:0 0;}
#yiv4312101745 #yiv4312101745ygrp-mkp .yiv4312101745ad p {
margin:0;}
#yiv4312101745 #yiv4312101745ygrp-mkp .yiv4312101745ad a {
color:#0000ff;text-decoration:none;}
#yiv4312101745 #yiv4312101745ygrp-sponsor
#yiv4312101745ygrp-lc {
font-family:Arial;}
#yiv4312101745 #yiv4312101745ygrp-sponsor
#yiv4312101745ygrp-lc #yiv4312101745hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4312101745 #yiv4312101745ygrp-sponsor
#yiv4312101745ygrp-lc .yiv4312101745ad {
margin-bottom:10px;padding:0 0;}
#yiv4312101745 #yiv4312101745actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4312101745 #yiv4312101745activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4312101745 #yiv4312101745activity span {
font-weight:700;}
#yiv4312101745 #yiv4312101745activity span:first-child {
text-transform:uppercase;}
#yiv4312101745 #yiv4312101745activity span a {
color:#5085b6;text-decoration:none;}
#yiv4312101745 #yiv4312101745activity span span {
color:#ff7900;}
#yiv4312101745 #yiv4312101745activity span
.yiv4312101745underline {
text-decoration:underline;}
#yiv4312101745 .yiv4312101745attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4312101745 .yiv4312101745attach div a {
text-decoration:none;}
#yiv4312101745 .yiv4312101745attach img {
border:none;padding-right:5px;}
#yiv4312101745 .yiv4312101745attach label {
display:block;margin-bottom:5px;}
#yiv4312101745 .yiv4312101745attach label a {
text-decoration:none;}
#yiv4312101745 blockquote {
margin:0 0 0 4px;}
#yiv4312101745 .yiv4312101745bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4312101745 .yiv4312101745bold a {
text-decoration:none;}
#yiv4312101745 dd.yiv4312101745last p a {
font-family:Verdana;font-weight:700;}
#yiv4312101745 dd.yiv4312101745last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4312101745 dd.yiv4312101745last p
span.yiv4312101745yshortcuts {
margin-right:0;}
#yiv4312101745 div.yiv4312101745attach-table div div a {
text-decoration:none;}
#yiv4312101745 div.yiv4312101745attach-table {
width:400px;}
#yiv4312101745 div.yiv4312101745file-title a, #yiv4312101745
div.yiv4312101745file-title a:active, #yiv4312101745
div.yiv4312101745file-title a:hover, #yiv4312101745
div.yiv4312101745file-title a:visited {
text-decoration:none;}
#yiv4312101745 div.yiv4312101745photo-title a,
#yiv4312101745 div.yiv4312101745photo-title a:active,
#yiv4312101745 div.yiv4312101745photo-title a:hover,
#yiv4312101745 div.yiv4312101745photo-title a:visited {
text-decoration:none;}
#yiv4312101745 div#yiv4312101745ygrp-mlmsg
#yiv4312101745ygrp-msg p a span.yiv4312101745yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4312101745 .yiv4312101745green {
color:#628c2a;}
#yiv4312101745 .yiv4312101745MsoNormal {
margin:0 0 0 0;}
#yiv4312101745 o {
font-size:0;}
#yiv4312101745 #yiv4312101745photos div {
float:left;width:72px;}
#yiv4312101745 #yiv4312101745photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4312101745 #yiv4312101745photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4312101745 #yiv4312101745reco-category {
font-size:77%;}
#yiv4312101745 #yiv4312101745reco-desc {
font-size:77%;}
#yiv4312101745 .yiv4312101745replbq {
margin:4px;}
#yiv4312101745 #yiv4312101745ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg select,
#yiv4312101745 input, #yiv4312101745 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg pre, #yiv4312101745
code {
font:115% monospace;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg * {
line-height:1.22em;}
#yiv4312101745 #yiv4312101745ygrp-mlmsg #yiv4312101745logo {
padding-bottom:10px;}
#yiv4312101745 #yiv4312101745ygrp-msg p a {
font-family:Verdana;}
#yiv4312101745 #yiv4312101745ygrp-msg
p#yiv4312101745attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4312101745 #yiv4312101745ygrp-reco
#yiv4312101745reco-head {
color:#ff7900;font-weight:700;}
#yiv4312101745 #yiv4312101745ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4312101745 #yiv4312101745ygrp-sponsor #yiv4312101745ov
li a {
font-size:130%;text-decoration:none;}
#yiv4312101745 #yiv4312101745ygrp-sponsor #yiv4312101745ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4312101745 #yiv4312101745ygrp-sponsor #yiv4312101745ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4312101745 #yiv4312101745ygrp-text {
font-family:Georgia;}
#yiv4312101745 #yiv4312101745ygrp-text p {
margin:0 0 1em 0;}
#yiv4312101745 #yiv4312101745ygrp-text tt {
font-size:120%;}
#yiv4312101745 #yiv4312101745ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv4312101745
|
Again, this could be related to open resistors in the horizontal deflection amplifier output stage. Specifically I would check R238, R239, and R275. These are the component references from the 8558B Operation and Service Manual (not the military version). The most common failure that I have encountered is R238 and/or R275 either open, or waaaaay off from the correct value (12.1K ohms).
|
Woops - forget my reference to the 8558B in my prior response - too many threads. :)? The remainder of the post is correct (i.e. look a the non-military manual for the unit).
Ken
|
Hi Andrew
?
You seam to be going in circles as you say
I don't have a signal generator I
posted text below on Sunday 8 oct
Basically you do have a signal
generator on the scope it is called the calibrator and if working produces a 10
volt square wave
From you posting to date it appears the vertical amps are working
But you say the horizontal control has no effect if so then the text
below will help narrow down the fault
?
There are a number of different plug ins so it might help if you posted
the plug in numbers there should be one for the left vertical and one for the
right time base
we can explain about x time base triggering after you have proved the
simple test below
?
Hi re fixing 180 from memory
Before removing the transistors a simple
test
Have you tested all the power supply rails
on the pcb for the main frame for this test I would remove the plugging just in
case they are causing any problems ?
?
Display switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier into external with the
intensity turned up you should have a spot
turning the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one down magnifier
should be set to 1 )
now connect a signal into the external
?BNC input below ?I just held a length of wire and put into the bnc
socket ?you should see a horizontal line if not it is probably the drive
transistors
if you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots one on left one
on right if one hasten moved then it is that pare of transistors that has a
fault
?
this was my first HP scope to repair
?Paul B
?
From:
hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]
Sent: 11 October 2017 02:11
To: hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
?
?
Thanks for the help. What can I use for a signal? I
don't have a signal generator. I tried testing it with a 3v 800ma wall wart
using the EXT INPUT and didn't get a dot or anything.
I tried using a 1.5v battery on the lower left input probe and, while holding
the test button down I could see the dot jump up and down 1.5 square up each
time I contacted the battery terminal. I can't get a dot to appear without
holding the test button, so I feel like the knobs and switches probably aren't
adjusted correctly.
It worked the same way with the lower left INPUT when I tried the wall wart.
The dot jumped up 3 squares, but only when holding the test beam button.
Do you think I'm doing the test correctly, or are there other switches and
knobs I need to try different settings with?
Thank again!
Andrew
--------------------------------------------
On Sun, 10/8/17, 'Paul
Bicknell' paul@...
[hp_agilent_equipment] <hp_agilent_equipment@...>
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 1:05 PM
?
Hi re
fixing 180 from memory
Before
removing the transistors a simple
test
Have
you tested all the power supply rails
on the pcb for the main frame for this test I would remove
the plugging just in
case they are causing any problems ?
?
Display
switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier into
external with the intensity
turned up you should have a spot
turning
the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one
down magnifier
should be set to 1 )
now
connect a signal into the external ?BNC
input below ?I just held a length of wire and put into the
bnc socket ?you
should see a horizontal line if not it is probably the drive
transistors
if
you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots
one on left one
on right if one hasten moved then it is that pare of
transistors that has a
fault
?
this
was my first HP scope to repair ?Paul
B
From:
hp_agilent_equipment@...
[mailto: hp_agilent_equipment@...
]
Sent: 08
October 2017 18:02
To:
hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs
repair ( San Antonio TX )
?
?
I have a fluke
digital multimeter, a weller soldering
station, and not much else. I'm slowly building up what
I can when I have a
specific need or find a good deal.
I bought a set of probes for it off ebay
http://www.ebay.com/itm/P6100-2PCS-Oscilloscope-Probe-Kit-100-MHz-Clip-Test-Probe-For-Tektronix-HP-Rigol/322409718031?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
There's no rush for me to fix it, so I can take the next
10 years if need be. Should
I de-solder the transistors for testing?
I heard that with very high voltages, the thickness of the
gloves are what's
important. That's why lineman's gloves and spark
plug boots are so thick.
I have a thick pair of rubber gloves that I'll probably
be wearing for safety
after leaving it unplugged for a while.
I also need to make a high resistance capacitor discharge
tool. I believe I
have some high capacity resistors I've salvaged from
some equipment.
Thanks for the tips. Any further help is appreciated.
Andrew
--------------------------------------------
On Sun, 10/8/17, Reginald Beardsley pulaskite@...
[hp_agilent_equipment]
< hp_agilent_equipment@...
>
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A
Oscilliscope needs repair ( San
Antonio TX )
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 11:30 AM
?
What test gear do you have? That will help people
advise you. Did it come with a probe?
The manual suggests approaches appropriate to a
commercial
environment where labor is expensive and parts are
readily
obtained. In your case labor is actually what you're
after. Except you'll call it "experience"
after you're done. Being able to say you have
repaired
a 100 MHz analog scope is non-trivial. That's a good
scope, though old age will make it a bit cranky. It will
serve you well even when you get newer gear.
You can make a limited test of the transistors by
measuring
the forward resistance of the B-E and B-C junctions with
an
ohmmeter. The B-C resistance will be smaller than the B-E
resistance because the larger area of the collector
trumps
the higher doping level of the emitter. Use the highest
resistance ranges. You may encounter problems with DMMs
that don't supply sufficient voltage to turn on the
transistor. I learned this trick using an analog VOM. It
doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that
they
give away, measure hFE with it. That should suffice for
testing the two transistors, But beware of the crappy
transistor sockets, You should probably solder some leads
with grabbers or alligator clips. I just tried two red
ones. One worked, the other didn't, but both were
intermittent. An old yellow HF DMM had a better socket
and
worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing.
Make
sure you know where the high voltages are and stay away
from
them. I've heard it's rather painful at best and
lethal at worst. If you do need to work near it, keep
your
left hand in your pocket and wear rubber sole shoes. HF
nitrile gloves might not be a bad idea, though I
don't
know how good they'd be. Not quite sure what is
recommended for southpaws. Be aware that the HV
capacitors
and the CRT can hold a charge for quite a while. Before
you
EVER touch anything in the HV section, ground it with a
screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over
a
week to fix the horizontal section in my Dumont
working a
couple of hours each evening.
Most important....
Have Fun!
Reg
#yiv4333658034 #yiv4333658034 --
#yiv4333658034ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034ads {
margin-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad {
padding:0 0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad p
{
margin:0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad a
{
color:#0000ff;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc {
font-family:Arial;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc #yiv4333658034hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc .yiv4333658034ad {
margin-bottom:10px;padding:0 0;}
#yiv4333658034 #yiv4333658034actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4333658034 #yiv4333658034activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4333658034 #yiv4333658034activity span {
font-weight:700;}
#yiv4333658034 #yiv4333658034activity span:first-child {
text-transform:uppercase;}
#yiv4333658034 #yiv4333658034activity span a {
color:#5085b6;text-decoration:none;}
#yiv4333658034 #yiv4333658034activity span span {
color:#ff7900;}
#yiv4333658034 #yiv4333658034activity span
.yiv4333658034underline {
text-decoration:underline;}
#yiv4333658034 .yiv4333658034attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4333658034 .yiv4333658034attach div a {
text-decoration:none;}
#yiv4333658034 .yiv4333658034attach img {
border:none;padding-right:5px;}
#yiv4333658034 .yiv4333658034attach label {
display:block;margin-bottom:5px;}
#yiv4333658034 .yiv4333658034attach label a {
text-decoration:none;}
#yiv4333658034 blockquote {
margin:0 0 0 4px;}
#yiv4333658034 .yiv4333658034bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4333658034 .yiv4333658034bold a {
text-decoration:none;}
#yiv4333658034 dd.yiv4333658034last p a {
font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p
span.yiv4333658034yshortcuts {
margin-right:0;}
#yiv4333658034 div.yiv4333658034attach-table div div a {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034attach-table {
width:400px;}
#yiv4333658034 div.yiv4333658034file-title a,
#yiv4333658034
div.yiv4333658034file-title a:active, #yiv4333658034
div.yiv4333658034file-title a:hover, #yiv4333658034
div.yiv4333658034file-title a:visited {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034photo-title a,
#yiv4333658034 div.yiv4333658034photo-title a:active,
#yiv4333658034 div.yiv4333658034photo-title a:hover,
#yiv4333658034 div.yiv4333658034photo-title a:visited {
text-decoration:none;}
#yiv4333658034 div#yiv4333658034ygrp-mlmsg
#yiv4333658034ygrp-msg p a span.yiv4333658034yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4333658034 .yiv4333658034green {
color:#628c2a;}
#yiv4333658034 .yiv4333658034MsoNormal {
margin:0 0 0 0;}
#yiv4333658034 o {
font-size:0;}
#yiv4333658034 #yiv4333658034photos div {
float:left;width:72px;}
#yiv4333658034 #yiv4333658034photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4333658034 #yiv4333658034photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4333658034 #yiv4333658034reco-category {
font-size:77%;}
#yiv4333658034 #yiv4333658034reco-desc {
font-size:77%;}
#yiv4333658034 .yiv4333658034replbq {
margin:4px;}
#yiv4333658034 #yiv4333658034ygrp-actbar div a:first-child
{
margin-right:2px;padding-right:5px;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg select,
#yiv4333658034 input, #yiv4333658034 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg pre,
#yiv4333658034
code {
font:115% monospace;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg * {
line-height:1.22em;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg #yiv4333658034logo
{
padding-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-msg p a {
font-family:Verdana;}
#yiv4333658034 #yiv4333658034ygrp-msg
p#yiv4333658034attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco
#yiv4333658034reco-head {
color:#ff7900;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li a {
font-size:130%;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4333658034 #yiv4333658034ygrp-text {
font-family: Georgia
;}
#yiv4333658034 #yiv4333658034ygrp-text p {
margin:0 0 1em 0;}
#yiv4333658034 #yiv4333658034ygrp-text tt {
font-size:120%;}
#yiv4333658034 #yiv4333658034ygrp-vital ul li:last-child
{
border-right:none !important;
}
#yiv4333658034
No virus found in this
message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15018 - Release
Date: 10/08/17
#yiv7282166702 #yiv7282166702 --
#yiv7282166702ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702ads {
margin-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad {
padding:0 0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad p {
margin:0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad a {
color:#0000ff;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc {
font-family:Arial;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc #yiv7282166702hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc .yiv7282166702ad {
margin-bottom:10px;padding:0 0;}
#yiv7282166702 #yiv7282166702actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv7282166702 #yiv7282166702activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv7282166702 #yiv7282166702activity span {
font-weight:700;}
#yiv7282166702 #yiv7282166702activity span:first-child {
text-transform:uppercase;}
#yiv7282166702 #yiv7282166702activity span a {
color:#5085b6;text-decoration:none;}
#yiv7282166702 #yiv7282166702activity span span {
color:#ff7900;}
#yiv7282166702 #yiv7282166702activity span
.yiv7282166702underline {
text-decoration:underline;}
#yiv7282166702 .yiv7282166702attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv7282166702 .yiv7282166702attach div a {
text-decoration:none;}
#yiv7282166702 .yiv7282166702attach img {
border:none;padding-right:5px;}
#yiv7282166702 .yiv7282166702attach label {
display:block;margin-bottom:5px;}
#yiv7282166702 .yiv7282166702attach label a {
text-decoration:none;}
#yiv7282166702 blockquote {
margin:0 0 0 4px;}
#yiv7282166702 .yiv7282166702bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv7282166702 .yiv7282166702bold a {
text-decoration:none;}
#yiv7282166702 dd.yiv7282166702last p a {
font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p
span.yiv7282166702yshortcuts {
margin-right:0;}
#yiv7282166702 div.yiv7282166702attach-table div div a {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702attach-table {
width:400px;}
#yiv7282166702 div.yiv7282166702file-title a, #yiv7282166702
div.yiv7282166702file-title a:active, #yiv7282166702
div.yiv7282166702file-title a:hover, #yiv7282166702
div.yiv7282166702file-title a:visited {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702photo-title a,
#yiv7282166702 div.yiv7282166702photo-title a:active,
#yiv7282166702 div.yiv7282166702photo-title a:hover,
#yiv7282166702 div.yiv7282166702photo-title a:visited {
text-decoration:none;}
#yiv7282166702 div#yiv7282166702ygrp-mlmsg
#yiv7282166702ygrp-msg p a span.yiv7282166702yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv7282166702 .yiv7282166702green {
color:#628c2a;}
#yiv7282166702 .yiv7282166702MsoNormal {
margin:0 0 0 0;}
#yiv7282166702 o {
font-size:0;}
#yiv7282166702 #yiv7282166702photos div {
float:left;width:72px;}
#yiv7282166702 #yiv7282166702photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv7282166702 #yiv7282166702photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv7282166702 #yiv7282166702reco-category {
font-size:77%;}
#yiv7282166702 #yiv7282166702reco-desc {
font-size:77%;}
#yiv7282166702 .yiv7282166702replbq {
margin:4px;}
#yiv7282166702 #yiv7282166702ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg select,
#yiv7282166702 input, #yiv7282166702 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg pre, #yiv7282166702
code {
font:115% monospace;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg * {
line-height:1.22em;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg #yiv7282166702logo {
padding-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-msg p a {
font-family:Verdana;}
#yiv7282166702 #yiv7282166702ygrp-msg
p#yiv7282166702attach-count span {
color:#1E66AE;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco
#yiv7282166702reco-head {
color:#ff7900;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
li a {
font-size:130%;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv7282166702 #yiv7282166702ygrp-sponsor #yiv7282166702ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv7282166702 #yiv7282166702ygrp-text {
font-family:Georgia;}
#yiv7282166702 #yiv7282166702ygrp-text p {
margin:0 0 1em 0;}
#yiv7282166702 #yiv7282166702ygrp-text tt {
font-size:120%;}
#yiv7282166702 #yiv7282166702ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv7282166702
No virus found in this message.
Checked by AVG -
Version: 2016.0.8013 / Virus Database: 4782/15026 - Release Date: 10/10/17
|
Ok, I re-read your original post. Thank you for your patience.
I used the calibrator sockets on the left side of the screen with 1 piece of wire in the negative and 1 piece of wire in the 10v socket and tested with the upper right hand probe input. Nothing yet. Then I tried the same hookup with the lower left probe and got two dots, one about two grid lines above the other. They are not moving.
So that would suggest that the transistors are at fault, correct?
Best Regards, Andrew
-------------------------------------------
toggle quoted message
Show quoted text
On Wed, 10/11/17, 'Paul Bicknell' paul@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Wednesday, October 11, 2017, 1:00 PM
?
Hi
Andrew
?
You
seam to be going in circles as you say
I don't have a signal generator I
posted text below on Sunday 8 oct
Basically
you do have a signal
generator on the scope it is called the calibrator and if
working produces a 10
volt square wave
From you posting
to date it appears the vertical amps are working
But you say the
horizontal control has no effect if so then the text
below will help narrow down the fault
?
There are a
number of different plug ins so it might help if you posted
the plug in numbers there should be one for the left
vertical and one for the
right time base
we can explain
about x time base triggering after you have proved the
simple test below
?
Hi re
fixing 180 from memory
Before
removing the transistors a simple
test
Have
you tested all the power supply rails
on the pcb for the main frame for this test I would remove
the plugging just in
case they are causing any problems ?
?
Display
switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier into
external with the
intensity turned up you should have a spot
turning
the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one
down magnifier
should be set to 1 )
now
connect a signal into the external
?BNC input below ?I just held a length of wire and put
into the bnc
socket ?you should see a horizontal line if not it is
probably the drive
transistors
if
you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots
one on left one
on right if one hasten moved then it is that pare of
transistors that has a
fault
?
this
was my first HP scope to repair
?Paul B
?
From:
hp_agilent_equipment@...
[mailto: hp_agilent_equipment@... ]
Sent: 11
October 2017 02:11
To:
hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs
repair ( San Antonio TX )
?
?
Thanks for the
help. What can I use for a signal? I
don't have a signal generator. I tried testing it with a
3v 800ma wall wart
using the EXT INPUT and didn't get a dot or anything.
I tried using a 1.5v battery on the lower left input probe
and, while holding
the test button down I could see the dot jump up and down
1.5 square up each
time I contacted the battery terminal. I can't get a dot
to appear without
holding the test button, so I feel like the knobs and
switches probably aren't
adjusted correctly.
It worked the same way with the lower left INPUT when I
tried the wall wart.
The dot jumped up 3 squares, but only when holding the test
beam button.
Do you think I'm doing the test correctly, or are there
other switches and
knobs I need to try different settings with?
Thank again!
Andrew
--------------------------------------------
On Sun, 10/8/17, ' Paul
Bicknell ' paul@...
[hp_agilent_equipment] <
hp_agilent_equipment@... >
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A
Oscilliscope needs repair ( San Antonio TX )
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 1:05 PM
?
Hi re
fixing 180 from memory
Before
removing the transistors a simple
test
Have
you tested all the power supply rails
on the pcb for the main frame for this test I would
remove
the plugging just in
case they are causing any problems ?
?
Display
switch on right hand side 3rd
one down turn it clock wise this puts the X amplifier
into
external with the intensity
turned up you should have a spot
turning
the pot fully clock wise gives
maximum sensitivity ?( right hand side 2rd one
down magnifier
should be set to 1 )
now
connect a signal into the external ?BNC
input below ?I just held a length of wire and put into
the
bnc socket ?you
should see a horizontal line if not it is probably the
drive
transistors
if
you have movement connect the BNC input
below ?to the calibration terminal you should see 2 dots
one on left one
on right if one hasten moved then it is that pare of
transistors that has a
fault
?
this
was my first HP scope to repair ?Paul
B
From:
hp_agilent_equipment@...
[mailto: hp_agilent_equipment@...
]
Sent: 08
October 2017 18:02
To:
hp_agilent_equipment@...
Subject: RE:
[hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs
repair ( San Antonio TX )
?
?
I have a fluke
digital multimeter, a weller soldering
station, and not much else. I'm slowly building up
what
I can when I have a
specific need or find a good deal.
I bought a set of probes for it off ebay
There's no rush for me to fix it, so I can take the
next
10 years if need be. Should
I de-solder the transistors for testing?
I heard that with very high voltages, the thickness of
the
gloves are what's
important. That's why lineman's gloves and spark
plug boots are so thick.
I have a thick pair of rubber gloves that I'll
probably
be wearing for safety
after leaving it unplugged for a while.
I also need to make a high resistance capacitor discharge
tool. I believe I
have some high capacity resistors I've salvaged from
some equipment.
Thanks for the tips. Any further help is appreciated.
Andrew
--------------------------------------------
On Sun, 10/8/17, Reginald Beardsley pulaskite@...
[hp_agilent_equipment]
< hp_agilent_equipment@...
>
wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A
Oscilliscope needs repair ( San
Antonio TX )
To: hp_agilent_equipment@...
Date: Sunday, October 8, 2017, 11:30 AM
?
What test gear do you have? That will help people
advise you. Did it come with a probe?
The manual suggests approaches appropriate to a
commercial
environment where labor is expensive and parts are
readily
obtained. In your case labor is actually what you're
after. Except you'll call it "experience"
after you're done. Being able to say you have
repaired
a 100 MHz analog scope is non-trivial. That's a good
scope, though old age will make it a bit cranky. It will
serve you well even when you get newer gear.
You can make a limited test of the transistors by
measuring
the forward resistance of the B-E and B-C junctions with
an
ohmmeter. The B-C resistance will be smaller than the B-E
resistance because the larger area of the collector
trumps
the higher doping level of the emitter. Use the highest
resistance ranges. You may encounter problems with DMMs
that don't supply sufficient voltage to turn on the
transistor. I learned this trick using an analog VOM. It
doesn't work with the Harbor Freight cheapy DMMs.
If you've got one of the Harbor Freight DMMs that
they
give away, measure hFE with it. That should suffice for
testing the two transistors, But beware of the crappy
transistor sockets, You should probably solder some leads
with grabbers or alligator clips. I just tried two red
ones. One worked, the other didn't, but both were
intermittent. An old yellow HF DMM had a better socket
and
worked just fine (once I plugged it in correctly ;-)
Connect to the probe compensation signal for testing.
Make
sure you know where the high voltages are and stay away
from
them. I've heard it's rather painful at best and
lethal at worst. If you do need to work near it, keep
your
left hand in your pocket and wear rubber sole shoes. HF
nitrile gloves might not be a bad idea, though I
don't
know how good they'd be. Not quite sure what is
recommended for southpaws. Be aware that the HV
capacitors
and the CRT can hold a charge for quite a while. Before
you
EVER touch anything in the HV section, ground it with a
screwdriver first with the unit unplugged.
Whenever you get tired or confused, stop. It took me over
a
week to fix the horizontal section in my Dumont
working a
couple of hours each evening.
Most important....
Have Fun!
Reg
#yiv4333658034 #yiv4333658034 --
#yiv4333658034ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv4333658034 #yiv4333658034ygrp-mkp #yiv4333658034ads {
margin-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad {
padding:0 0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad p
{
margin:0;}
#yiv4333658034 #yiv4333658034ygrp-mkp .yiv4333658034ad a
{
color:#0000ff;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc {
font-family:Arial;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc #yiv4333658034hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ygrp-lc .yiv4333658034ad {
margin-bottom:10px;padding:0 0;}
#yiv4333658034 #yiv4333658034actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv4333658034 #yiv4333658034activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv4333658034 #yiv4333658034activity span {
font-weight:700;}
#yiv4333658034 #yiv4333658034activity span:first-child {
text-transform:uppercase;}
#yiv4333658034 #yiv4333658034activity span a {
color:#5085b6;text-decoration:none;}
#yiv4333658034 #yiv4333658034activity span span {
color:#ff7900;}
#yiv4333658034 #yiv4333658034activity span
.yiv4333658034underline {
text-decoration:underline;}
#yiv4333658034 .yiv4333658034attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv4333658034 .yiv4333658034attach div a {
text-decoration:none;}
#yiv4333658034 .yiv4333658034attach img {
border:none;padding-right:5px;}
#yiv4333658034 .yiv4333658034attach label {
display:block;margin-bottom:5px;}
#yiv4333658034 .yiv4333658034attach label a {
text-decoration:none;}
#yiv4333658034 blockquote {
margin:0 0 0 4px;}
#yiv4333658034 .yiv4333658034bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv4333658034 .yiv4333658034bold a {
text-decoration:none;}
#yiv4333658034 dd.yiv4333658034last p a {
font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv4333658034 dd.yiv4333658034last p
span.yiv4333658034yshortcuts {
margin-right:0;}
#yiv4333658034 div.yiv4333658034attach-table div div a {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034attach-table {
width:400px;}
#yiv4333658034 div.yiv4333658034file-title a,
#yiv4333658034
div.yiv4333658034file-title a:active, #yiv4333658034
div.yiv4333658034file-title a:hover, #yiv4333658034
div.yiv4333658034file-title a:visited {
text-decoration:none;}
#yiv4333658034 div.yiv4333658034photo-title a,
#yiv4333658034 div.yiv4333658034photo-title a:active,
#yiv4333658034 div.yiv4333658034photo-title a:hover,
#yiv4333658034 div.yiv4333658034photo-title a:visited {
text-decoration:none;}
#yiv4333658034 div#yiv4333658034ygrp-mlmsg
#yiv4333658034ygrp-msg p a span.yiv4333658034yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv4333658034 .yiv4333658034green {
color:#628c2a;}
#yiv4333658034 .yiv4333658034MsoNormal {
margin:0 0 0 0;}
#yiv4333658034 o {
font-size:0;}
#yiv4333658034 #yiv4333658034photos div {
float:left;width:72px;}
#yiv4333658034 #yiv4333658034photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv4333658034 #yiv4333658034photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv4333658034 #yiv4333658034reco-category {
font-size:77%;}
#yiv4333658034 #yiv4333658034reco-desc {
font-size:77%;}
#yiv4333658034 .yiv4333658034replbq {
margin:4px;}
#yiv4333658034 #yiv4333658034ygrp-actbar div
a:first-child
{
margin-right:2px;padding-right:5px;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg select,
#yiv4333658034 input, #yiv4333658034 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg pre,
#yiv4333658034
code {
font:115% monospace;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg * {
line-height:1.22em;}
#yiv4333658034 #yiv4333658034ygrp-mlmsg
#yiv4333658034logo
{
padding-bottom:10px;}
#yiv4333658034 #yiv4333658034ygrp-msg p a {
font-family:Verdana;}
#yiv4333658034 #yiv4333658034ygrp-msg
p#yiv4333658034attach-count span {
color:#1E66AE;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco
#yiv4333658034reco-head {
color:#ff7900;font-weight:700;}
#yiv4333658034 #yiv4333658034ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li a {
font-size:130%;text-decoration:none;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv4333658034 #yiv4333658034ygrp-sponsor
#yiv4333658034ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv4333658034 #yiv4333658034ygrp-text {
font-family: Georgia
;}
#yiv4333658034 #yiv4333658034ygrp-text p {
margin:0 0 1em 0;}
#yiv4333658034 #yiv4333658034ygrp-text tt {
font-size:120%;}
#yiv4333658034 #yiv4333658034ygrp-vital ul li:last-child
{
border-right:none !important;
}
#yiv4333658034
No virus found in this
message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15018 -
Release
Date: 10/08/17
#yiv7282166702 #yiv7282166702 --
#yiv7282166702ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv7282166702 #yiv7282166702ygrp-mkp #yiv7282166702ads {
margin-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad {
padding:0 0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad p
{
margin:0;}
#yiv7282166702 #yiv7282166702ygrp-mkp .yiv7282166702ad a
{
color:#0000ff;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc {
font-family:Arial;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc #yiv7282166702hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ygrp-lc .yiv7282166702ad {
margin-bottom:10px;padding:0 0;}
#yiv7282166702 #yiv7282166702actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv7282166702 #yiv7282166702activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv7282166702 #yiv7282166702activity span {
font-weight:700;}
#yiv7282166702 #yiv7282166702activity span:first-child {
text-transform:uppercase;}
#yiv7282166702 #yiv7282166702activity span a {
color:#5085b6;text-decoration:none;}
#yiv7282166702 #yiv7282166702activity span span {
color:#ff7900;}
#yiv7282166702 #yiv7282166702activity span
.yiv7282166702underline {
text-decoration:underline;}
#yiv7282166702 .yiv7282166702attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv7282166702 .yiv7282166702attach div a {
text-decoration:none;}
#yiv7282166702 .yiv7282166702attach img {
border:none;padding-right:5px;}
#yiv7282166702 .yiv7282166702attach label {
display:block;margin-bottom:5px;}
#yiv7282166702 .yiv7282166702attach label a {
text-decoration:none;}
#yiv7282166702 blockquote {
margin:0 0 0 4px;}
#yiv7282166702 .yiv7282166702bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv7282166702 .yiv7282166702bold a {
text-decoration:none;}
#yiv7282166702 dd.yiv7282166702last p a {
font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv7282166702 dd.yiv7282166702last p
span.yiv7282166702yshortcuts {
margin-right:0;}
#yiv7282166702 div.yiv7282166702attach-table div div a {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702attach-table {
width:400px;}
#yiv7282166702 div.yiv7282166702file-title a,
#yiv7282166702
div.yiv7282166702file-title a:active, #yiv7282166702
div.yiv7282166702file-title a:hover, #yiv7282166702
div.yiv7282166702file-title a:visited {
text-decoration:none;}
#yiv7282166702 div.yiv7282166702photo-title a,
#yiv7282166702 div.yiv7282166702photo-title a:active,
#yiv7282166702 div.yiv7282166702photo-title a:hover,
#yiv7282166702 div.yiv7282166702photo-title a:visited {
text-decoration:none;}
#yiv7282166702 div#yiv7282166702ygrp-mlmsg
#yiv7282166702ygrp-msg p a span.yiv7282166702yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv7282166702 .yiv7282166702green {
color:#628c2a;}
#yiv7282166702 .yiv7282166702MsoNormal {
margin:0 0 0 0;}
#yiv7282166702 o {
font-size:0;}
#yiv7282166702 #yiv7282166702photos div {
float:left;width:72px;}
#yiv7282166702 #yiv7282166702photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv7282166702 #yiv7282166702photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv7282166702 #yiv7282166702reco-category {
font-size:77%;}
#yiv7282166702 #yiv7282166702reco-desc {
font-size:77%;}
#yiv7282166702 .yiv7282166702replbq {
margin:4px;}
#yiv7282166702 #yiv7282166702ygrp-actbar div a:first-child
{
margin-right:2px;padding-right:5px;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg select,
#yiv7282166702 input, #yiv7282166702 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg pre,
#yiv7282166702
code {
font:115% monospace;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg * {
line-height:1.22em;}
#yiv7282166702 #yiv7282166702ygrp-mlmsg #yiv7282166702logo
{
padding-bottom:10px;}
#yiv7282166702 #yiv7282166702ygrp-msg p a {
font-family:Verdana;}
#yiv7282166702 #yiv7282166702ygrp-msg
p#yiv7282166702attach-count span {
color:#1E66AE;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco
#yiv7282166702reco-head {
color:#ff7900;font-weight:700;}
#yiv7282166702 #yiv7282166702ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ov
li a {
font-size:130%;text-decoration:none;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv7282166702 #yiv7282166702ygrp-sponsor
#yiv7282166702ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv7282166702 #yiv7282166702ygrp-text {
font-family: Georgia ;}
#yiv7282166702 #yiv7282166702ygrp-text p {
margin:0 0 1em 0;}
#yiv7282166702 #yiv7282166702ygrp-text tt {
font-size:120%;}
#yiv7282166702 #yiv7282166702ygrp-vital ul li:last-child
{
border-right:none !important;
}
#yiv7282166702
No virus found in this
message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15026 - Release
Date: 10/10/17
#yiv2109808339 #yiv2109808339 --
#yiv2109808339ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv2109808339 #yiv2109808339ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv2109808339 #yiv2109808339ygrp-mkp #yiv2109808339hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv2109808339 #yiv2109808339ygrp-mkp #yiv2109808339ads {
margin-bottom:10px;}
#yiv2109808339 #yiv2109808339ygrp-mkp .yiv2109808339ad {
padding:0 0;}
#yiv2109808339 #yiv2109808339ygrp-mkp .yiv2109808339ad p {
margin:0;}
#yiv2109808339 #yiv2109808339ygrp-mkp .yiv2109808339ad a {
color:#0000ff;text-decoration:none;}
#yiv2109808339 #yiv2109808339ygrp-sponsor
#yiv2109808339ygrp-lc {
font-family:Arial;}
#yiv2109808339 #yiv2109808339ygrp-sponsor
#yiv2109808339ygrp-lc #yiv2109808339hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv2109808339 #yiv2109808339ygrp-sponsor
#yiv2109808339ygrp-lc .yiv2109808339ad {
margin-bottom:10px;padding:0 0;}
#yiv2109808339 #yiv2109808339actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv2109808339 #yiv2109808339activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv2109808339 #yiv2109808339activity span {
font-weight:700;}
#yiv2109808339 #yiv2109808339activity span:first-child {
text-transform:uppercase;}
#yiv2109808339 #yiv2109808339activity span a {
color:#5085b6;text-decoration:none;}
#yiv2109808339 #yiv2109808339activity span span {
color:#ff7900;}
#yiv2109808339 #yiv2109808339activity span
.yiv2109808339underline {
text-decoration:underline;}
#yiv2109808339 .yiv2109808339attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv2109808339 .yiv2109808339attach div a {
text-decoration:none;}
#yiv2109808339 .yiv2109808339attach img {
border:none;padding-right:5px;}
#yiv2109808339 .yiv2109808339attach label {
display:block;margin-bottom:5px;}
#yiv2109808339 .yiv2109808339attach label a {
text-decoration:none;}
#yiv2109808339 blockquote {
margin:0 0 0 4px;}
#yiv2109808339 .yiv2109808339bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv2109808339 .yiv2109808339bold a {
text-decoration:none;}
#yiv2109808339 dd.yiv2109808339last p a {
font-family:Verdana;font-weight:700;}
#yiv2109808339 dd.yiv2109808339last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv2109808339 dd.yiv2109808339last p
span.yiv2109808339yshortcuts {
margin-right:0;}
#yiv2109808339 div.yiv2109808339attach-table div div a {
text-decoration:none;}
#yiv2109808339 div.yiv2109808339attach-table {
width:400px;}
#yiv2109808339 div.yiv2109808339file-title a, #yiv2109808339
div.yiv2109808339file-title a:active, #yiv2109808339
div.yiv2109808339file-title a:hover, #yiv2109808339
div.yiv2109808339file-title a:visited {
text-decoration:none;}
#yiv2109808339 div.yiv2109808339photo-title a,
#yiv2109808339 div.yiv2109808339photo-title a:active,
#yiv2109808339 div.yiv2109808339photo-title a:hover,
#yiv2109808339 div.yiv2109808339photo-title a:visited {
text-decoration:none;}
#yiv2109808339 div#yiv2109808339ygrp-mlmsg
#yiv2109808339ygrp-msg p a span.yiv2109808339yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv2109808339 .yiv2109808339green {
color:#628c2a;}
#yiv2109808339 .yiv2109808339MsoNormal {
margin:0 0 0 0;}
#yiv2109808339 o {
font-size:0;}
#yiv2109808339 #yiv2109808339photos div {
float:left;width:72px;}
#yiv2109808339 #yiv2109808339photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv2109808339 #yiv2109808339photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv2109808339 #yiv2109808339reco-category {
font-size:77%;}
#yiv2109808339 #yiv2109808339reco-desc {
font-size:77%;}
#yiv2109808339 .yiv2109808339replbq {
margin:4px;}
#yiv2109808339 #yiv2109808339ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg select,
#yiv2109808339 input, #yiv2109808339 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg pre, #yiv2109808339
code {
font:115% monospace;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg * {
line-height:1.22em;}
#yiv2109808339 #yiv2109808339ygrp-mlmsg #yiv2109808339logo {
padding-bottom:10px;}
#yiv2109808339 #yiv2109808339ygrp-msg p a {
font-family:Verdana;}
#yiv2109808339 #yiv2109808339ygrp-msg
p#yiv2109808339attach-count span {
color:#1E66AE;font-weight:700;}
#yiv2109808339 #yiv2109808339ygrp-reco
#yiv2109808339reco-head {
color:#ff7900;font-weight:700;}
#yiv2109808339 #yiv2109808339ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv2109808339 #yiv2109808339ygrp-sponsor #yiv2109808339ov
li a {
font-size:130%;text-decoration:none;}
#yiv2109808339 #yiv2109808339ygrp-sponsor #yiv2109808339ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv2109808339 #yiv2109808339ygrp-sponsor #yiv2109808339ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv2109808339 #yiv2109808339ygrp-text {
font-family:Georgia;}
#yiv2109808339 #yiv2109808339ygrp-text p {
margin:0 0 1em 0;}
#yiv2109808339 #yiv2109808339ygrp-text tt {
font-size:120%;}
#yiv2109808339 #yiv2109808339ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv2109808339
|
Great. Thank you!
--------------------------------------------
toggle quoted message
Show quoted text
On Tue, 10/10/17, knener@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Subject: RE: [hp_agilent_equipment] HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
To: hp_agilent_equipment@...
Date: Tuesday, October 10, 2017, 10:23 PM
?
Again, this could be related to open resistors in
the horizontal deflection amplifier output stage.
Specifically I would check R238, R239, and R275. These are
the component references from the 8558B Operation and
Service Manual (not the military version). The most common
failure that I have encountered is R238 and/or R275 either
open, or waaaaay off from the correct value (12.1K
ohms).
Ken
#yiv0689356414 #yiv0689356414 --
#yiv0689356414ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}
#yiv0689356414 #yiv0689356414ygrp-mkp hr {
border:1px solid #d8d8d8;}
#yiv0689356414 #yiv0689356414ygrp-mkp #yiv0689356414hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}
#yiv0689356414 #yiv0689356414ygrp-mkp #yiv0689356414ads {
margin-bottom:10px;}
#yiv0689356414 #yiv0689356414ygrp-mkp .yiv0689356414ad {
padding:0 0;}
#yiv0689356414 #yiv0689356414ygrp-mkp .yiv0689356414ad p {
margin:0;}
#yiv0689356414 #yiv0689356414ygrp-mkp .yiv0689356414ad a {
color:#0000ff;text-decoration:none;}
#yiv0689356414 #yiv0689356414ygrp-sponsor
#yiv0689356414ygrp-lc {
font-family:Arial;}
#yiv0689356414 #yiv0689356414ygrp-sponsor
#yiv0689356414ygrp-lc #yiv0689356414hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}
#yiv0689356414 #yiv0689356414ygrp-sponsor
#yiv0689356414ygrp-lc .yiv0689356414ad {
margin-bottom:10px;padding:0 0;}
#yiv0689356414 #yiv0689356414actions {
font-family:Verdana;font-size:11px;padding:10px 0;}
#yiv0689356414 #yiv0689356414activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}
#yiv0689356414 #yiv0689356414activity span {
font-weight:700;}
#yiv0689356414 #yiv0689356414activity span:first-child {
text-transform:uppercase;}
#yiv0689356414 #yiv0689356414activity span a {
color:#5085b6;text-decoration:none;}
#yiv0689356414 #yiv0689356414activity span span {
color:#ff7900;}
#yiv0689356414 #yiv0689356414activity span
.yiv0689356414underline {
text-decoration:underline;}
#yiv0689356414 .yiv0689356414attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}
#yiv0689356414 .yiv0689356414attach div a {
text-decoration:none;}
#yiv0689356414 .yiv0689356414attach img {
border:none;padding-right:5px;}
#yiv0689356414 .yiv0689356414attach label {
display:block;margin-bottom:5px;}
#yiv0689356414 .yiv0689356414attach label a {
text-decoration:none;}
#yiv0689356414 blockquote {
margin:0 0 0 4px;}
#yiv0689356414 .yiv0689356414bold {
font-family:Arial;font-size:13px;font-weight:700;}
#yiv0689356414 .yiv0689356414bold a {
text-decoration:none;}
#yiv0689356414 dd.yiv0689356414last p a {
font-family:Verdana;font-weight:700;}
#yiv0689356414 dd.yiv0689356414last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}
#yiv0689356414 dd.yiv0689356414last p
span.yiv0689356414yshortcuts {
margin-right:0;}
#yiv0689356414 div.yiv0689356414attach-table div div a {
text-decoration:none;}
#yiv0689356414 div.yiv0689356414attach-table {
width:400px;}
#yiv0689356414 div.yiv0689356414file-title a, #yiv0689356414
div.yiv0689356414file-title a:active, #yiv0689356414
div.yiv0689356414file-title a:hover, #yiv0689356414
div.yiv0689356414file-title a:visited {
text-decoration:none;}
#yiv0689356414 div.yiv0689356414photo-title a,
#yiv0689356414 div.yiv0689356414photo-title a:active,
#yiv0689356414 div.yiv0689356414photo-title a:hover,
#yiv0689356414 div.yiv0689356414photo-title a:visited {
text-decoration:none;}
#yiv0689356414 div#yiv0689356414ygrp-mlmsg
#yiv0689356414ygrp-msg p a span.yiv0689356414yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}
#yiv0689356414 .yiv0689356414green {
color:#628c2a;}
#yiv0689356414 .yiv0689356414MsoNormal {
margin:0 0 0 0;}
#yiv0689356414 o {
font-size:0;}
#yiv0689356414 #yiv0689356414photos div {
float:left;width:72px;}
#yiv0689356414 #yiv0689356414photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}
#yiv0689356414 #yiv0689356414photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}
#yiv0689356414 #yiv0689356414reco-category {
font-size:77%;}
#yiv0689356414 #yiv0689356414reco-desc {
font-size:77%;}
#yiv0689356414 .yiv0689356414replbq {
margin:4px;}
#yiv0689356414 #yiv0689356414ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg table {
font-size:inherit;font:100%;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg select,
#yiv0689356414 input, #yiv0689356414 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg pre, #yiv0689356414
code {
font:115% monospace;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg * {
line-height:1.22em;}
#yiv0689356414 #yiv0689356414ygrp-mlmsg #yiv0689356414logo {
padding-bottom:10px;}
#yiv0689356414 #yiv0689356414ygrp-msg p a {
font-family:Verdana;}
#yiv0689356414 #yiv0689356414ygrp-msg
p#yiv0689356414attach-count span {
color:#1E66AE;font-weight:700;}
#yiv0689356414 #yiv0689356414ygrp-reco
#yiv0689356414reco-head {
color:#ff7900;font-weight:700;}
#yiv0689356414 #yiv0689356414ygrp-reco {
margin-bottom:20px;padding:0px;}
#yiv0689356414 #yiv0689356414ygrp-sponsor #yiv0689356414ov
li a {
font-size:130%;text-decoration:none;}
#yiv0689356414 #yiv0689356414ygrp-sponsor #yiv0689356414ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}
#yiv0689356414 #yiv0689356414ygrp-sponsor #yiv0689356414ov
ul {
margin:0;padding:0 0 0 8px;}
#yiv0689356414 #yiv0689356414ygrp-text {
font-family:Georgia;}
#yiv0689356414 #yiv0689356414ygrp-text p {
margin:0 0 1em 0;}
#yiv0689356414 #yiv0689356414ygrp-text tt {
font-size:120%;}
#yiv0689356414 #yiv0689356414ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv0689356414
|
Paul Bicknell