Free for postage: Texscan VS-90B sweep generator instruction and operating manual
Hello--
Not for an HP nor a Tektronix product, this manual consists of a commercially-sold
and bound copy of the manual for Texscan's VS-90B sweep generator (covering 5 MHz to 2.35 GHz in three bands).
The manual includes copies of the instrument's schematics-- quality of these "copies of copies" varies from good to somewhat legible.
Questions welcomed, PayPal honored for postage.
73--
brad AA1IP
|
Re: [TekScopes] Re: Chinese-made reflow soldering ovens
I found this:
On Sunday, October 8, 2017 1:43 PM, "Bryce Schroeder bryce.schroeder@... [TekScopes]" <TekScopes@...> wrote:
?
Yes, I have one, it works okay after a third-party firmware mod and some
minor hardware modifications (notably the firmware mod supports a
temperature reference; the stock firmware just assumes iirc that the cold
junction is always 21C or thereabouts, which is definitely not the case, as
it is positioned over the oven...)
The one I got also had masking tape used inside it to hold the insulation,
I replaced it with kapton tape. I don't know if they still come with
masking tape. The earthing connection to the case was also iffy looking and
I improved it a bit. There was a tutorial about modding these things online
somewhere which was important to do at the time I got mine, I don't know if
the stock machine has improved in the couple years since I got mine.
Good luck.
On 8 October 2017 at 16:40, 'Dave M' dgminala@...
[hp_agilent_equipment]
>
>
> Anyone have any experience or have colleagues who have experience using
> the Chinese-made reflow soldering ovens such as those being sold on the
> evil auction place? The one I've looked at is item number:262955348183
> (Model T962).
>
> My eyes have become the major challenge to producing the one- or two-off
> projects, since many of the parts that are available today are only made in
> SMD packages. I realize that placing them onto the board still remains a
> challenge, but at least with a proper oven, I won't have to hold a
> soldering iron steady enough to build the boards.
>
> This model seems to be big enough to handle all the boards that I want to
> make, so that is a plus. Just wondering if this model produces good boards
> with no unsoldered areas, damaged components, etc. If it can consistently
> produce good boards, I'll take a chance on one of them. Reading the
> Chinglish instructions is scary enough , but maybe I can figure it out well
> enough to make it work.
>
> Hope someone can give good advice
>
> Dave M
>
>
>
>
|
Re: Chinese-made reflow soldering ovens
Yes, I have one, it works okay after a third-party firmware mod and some minor hardware modifications (notably the firmware mod supports a temperature reference; the stock firmware just assumes iirc that the cold junction is always 21C or thereabouts, which is definitely not the case, as it is positioned over the oven...)
The one I got also had masking tape used inside it to hold the insulation, I replaced it with kapton tape. I don't know if they still come with masking tape. The earthing connection to the case was also iffy looking and I improved it a bit. There was a tutorial about modding these things online somewhere which was important to do at the time I got mine, I don't know if the stock machine has improved in the couple years since I got mine. Good luck.
On 8 October 2017 at 16:40, 'Dave M' dgminala@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Anyone have any experience or have colleagues who have experience using the
Chinese-made reflow soldering ovens such as those being sold on the evil auction
place?? The one I've looked at is?item number:262955348183 (Model
T962).?
?
My eyes have become the major challenge?to producing the one- or
two-off projects, since many of the parts that?are available today?are
only made in SMD packages.?? I realize that placing them onto the
board still remains a challenge, but at least with a proper oven, I won't have
to hold a soldering iron steady enough to build the boards.
?
This model seems to be big enough to?handle all the boards that I want
to make, so that is a plus.? Just wondering if this model produces good
boards with no unsoldered areas, damaged components, etc.? If it can
consistently produce good boards, I'll take a chance on one of them.?
Reading the Chinglish instructions is scary enough , but maybe I can figure it
out well enough to make it work.
?
Hope someone can give good advice
Dave M
|
Chinese-made reflow soldering ovens
Anyone have any experience or have colleagues who have experience using the
Chinese-made reflow soldering ovens such as those being sold on the evil auction
place?? The one I've looked at is?item number:262955348183 (Model
T962).?
?
My eyes have become the major challenge?to producing the one- or
two-off projects, since many of the parts that?are available today?are
only made in SMD packages.?? I realize that placing them onto the
board still remains a challenge, but at least with a proper oven, I won't have
to hold a soldering iron steady enough to build the boards.
?
This model seems to be big enough to?handle all the boards that I want
to make, so that is a plus.? Just wondering if this model produces good
boards with no unsoldered areas, damaged components, etc.? If it can
consistently produce good boards, I'll take a chance on one of them.?
Reading the Chinglish instructions is scary enough , but maybe I can figure it
out well enough to make it work.
?
Hope someone can give good advice
Dave M
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
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
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
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
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|
Re: HP854A Test Oscillator with worn out attenuator
Hi Alan Thank you for that suggestion. That seems much more sensible than my plan. Perhaps the external attenuator could be made from the 0.25% resistors from the old unit. It is an 654A which only goes up to 10 MHz. My jobs are usually on low noise monitoring and DC stability measurements.?Chris
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
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.
|
Re: HP854A Test Oscillator with worn out attenuator
Oh, I assume you are addressing an 8654A?
On Sunday, October 8, 2017 10:29 AM, "alan victor amvictor88@... [hp_agilent_equipment]" wrote:
?
Hi Chris,
If it were my generator, I would look at the effort involved with your approach as opposed to fixing the power output at a constant level. Will assume the ALC or power leveling is accomplished. Then get a set of 1 dB and 10 dB step attenuator external to the instrument. Continuous 120 dB variable attenuator are available at reasonable prices. For the receiver sensitivity this is what I use vs. the usual step attenuator in the generator. Alan
On Sunday, October 8, 2017 9:29 AM, "krizhz@... [hp_agilent_equipment]" wrote:
?
Hello
I found this 854A on eBay recently and thought I could fix it. Unfortunately the frequency range switch is rather worn and the attenuator seems to be beyond repair. I've tried re-setting some contacts to use a fresh bit of rotor, but most contacts are hard to get at. This attenuator has 18 wafers, mostly double sided and 10 inter-wafer screens which have been used as solder tags. The rest of the machine is amazing quality as you would expect from HP, but the switch is cheap Paxolin (srbf). If I were to replace the whole assembly with 16 DPDT 24 volt reed relays and 2 x 10 way single rotor switches with diode decoding, do you think the minus 26 volt power supply could supply the 480 mA maximum coil current? It's an extra 12 Watts on top of the 32 Watts that the instrument as a whole uses. Any suggestions would be gratefully received. Chris Hayes
|
Re: HP854A Test Oscillator with worn out attenuator
Hi Chris,
If it were my generator, I would look at the effort involved with your approach as opposed to fixing the power output at a constant level. Will assume the ALC or power leveling is accomplished. Then get a set of 1 dB and 10 dB step attenuator external to the instrument. Continuous 120 dB variable attenuator are available at reasonable prices. For the receiver sensitivity this is what I use vs. the usual step attenuator in the generator. Alan
On Sunday, October 8, 2017 9:29 AM, "krizhz@... [hp_agilent_equipment]" wrote:
?
Hello
I found this 854A on eBay recently and thought I could fix it. Unfortunately the frequency range switch is rather worn and the attenuator seems to be beyond repair. I've tried re-setting some contacts to use a fresh bit of rotor, but most contacts are hard to get at. This attenuator has 18 wafers, mostly double sided and 10 inter-wafer screens which have been used as solder tags. The rest of the machine is amazing quality as you would expect from HP, but the switch is cheap Paxolin (srbf). If I were to replace the whole assembly with 16 DPDT 24 volt reed relays and 2 x 10 way single rotor switches with diode decoding, do you think the minus 26 volt power supply could supply the 480 mA maximum coil current? It's an extra 12 Watts on top of the 32 Watts that the instrument as a whole uses. Any suggestions would be gratefully received. Chris Hayes
|
Re: 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
--------------------------------------------
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
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Re: Affordable VNA Cal Kit in 12~15Ghz
Calvin,
For your VNA measurement (12-15 GHz), and considering the budget, I would get a sliding load and a set of HP shorts/opens on ebay. I say "HP" because the calibration constants for those are published. Maury Microwave also made them and those numbers can be obtained too. All this can be purchased at reasonable cost if you get the parts as individual pieces or incomplete kits. Sliding loads are rarely used these days, so they show up at reasonable cost. HP and Maury made them. Also, get the free software for editing and sending calibration coefficients to the 8510 via HPIB. It's called VNA Cal Kit Manager. Your biggest problem will be understanding the terminology and conventions regarding the data entry into the analyzer. They didn't make it simple. Also beware of the "male"/"female" conventions with regard to port connectors. They changed them at some point.
The 8510 was the last of the VNAs with high performance test sets. For many applications, the analyzer was good enough to use without calibration. However the test port cables are always a problem and this is where you are stuck.
Vladan
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
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
|
Re: Slightly off topic puzzle
Seems you have a period where it operates ok until it warms up. How about using some 'canned air' to spray cool/cold air at different things till you find the spurious item....(if you turn the can upside down, it makes a near cryogenic spray)
Dan in Chandler, AZ
|
HP854A Test Oscillator with worn out attenuator
Hello
I found this 854A on eBay recently and thought I could fix it. Unfortunately the frequency range switch is rather worn and the attenuator seems to be beyond repair. I've tried re-setting some contacts to use a fresh bit of rotor, but most contacts are hard to get at. This attenuator has 18 wafers, mostly double sided and 10 inter-wafer screens which have been used as solder tags. The rest of the machine is amazing quality as you would expect from HP, but the switch is cheap Paxolin (srbf). If I were to replace the whole assembly with 16 DPDT 24 volt reed relays and 2 x 10 way single rotor switches with diode decoding, do you think the minus 26 volt power supply could supply the 480 mA maximum coil current? It's an extra 12 Watts on top of the 32 Watts that the instrument as a whole uses. Any suggestions would be gratefully received. Chris Hayes
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
?
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?
|
Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
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
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Re: HP AN/USM 281A Oscilliscope needs repair (San Antonio TX)
"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
|
Re: Affordable VNA Cal Kit in 12~15Ghz
Hello,
contact me offlist with Papers which interest you. I won a lawsuit some years ago...as long as you are Content with paper printouts, Bob should be your uncle.
---
With best regards
Tam HANNA (emailing on a BlackBerry PRIV)
Enjoy electronics? Join 6500 other followers by visiting the Crazy Electronics Lab at Am 8. Oktober 2017 15:55:36 MESZ schrieb "Reginald Beardsley pulaskite@... [hp_agilent_equipment]" :
?
Robert,
I would certainly agree that making an accurate load is the hard part. The techniques I'm referencing bypass that. They were developed by research staff at the various standards institutes and rely on clever algebra and first principles.
Take a look at the paper. It's short and there is no need to read the math. Just look at the figures and read the introduction. The problem with making an accurate load is getting the reflection to be zero. The connector guarantees that it will never be zero. The TRR paper avoids that by allowing the reflection coefficients to be unknowns which are eliminated algebraically. OSL is convenient, but has the serious issue of requiring a calibrated instrument to characterize the load. Before you can do that accurately you need a calibration method that does not depend upon OSL.
There are a slew of techniques that have been published. Most I can't access. Of the ones I could, TRR seemed the easiest to implement. I've not been able to obtain a copy of Engen & Hoer's 6 port paper, but it appears to be a tapped transmission line which should also be easy to implement but I think it requires maintaining tolerances of 0.001" at 15 GHz to achieve ~1% accuracy. Doable, but definitely not easy.
Prior to Joseph Whitworth, no on knew how to make a flat surface. Whitworth became justifiably famous for showing how to do that in the 19th century along with consistent measurements to a millionth of an inch. The construction of a surface plate is a physical exercise in algebra. You have to make 3 at once and compare and correct them in a specific order.
Have Fun!
Reg
|
Re: Affordable VNA Cal Kit in 12~15Ghz
Robert,
I would certainly agree that making an accurate load is the hard part. The techniques I'm referencing bypass that. They were developed by research staff at the various standards institutes and rely on clever algebra and first principles.
Take a look at the paper. It's short and there is no need to read the math. Just look at the figures and read the introduction. The problem with making an accurate load is getting the reflection to be zero. The connector guarantees that it will never be zero. The TRR paper avoids that by allowing the reflection coefficients to be unknowns which are eliminated algebraically. OSL is convenient, but has the serious issue of requiring a calibrated instrument to characterize the load. Before you can do that accurately you need a calibration method that does not depend upon OSL.
There are a slew of techniques that have been published. Most I can't access. Of the ones I could, TRR seemed the easiest to implement. I've not been able to obtain a copy of Engen & Hoer's 6 port paper, but it appears to be a tapped transmission line which should also be easy to implement but I think it requires maintaining tolerances of 0.001" at 15 GHz to achieve ~1% accuracy. Doable, but definitely not easy.
Prior to Joseph Whitworth, no on knew how to make a flat surface. Whitworth became justifiably famous for showing how to do that in the 19th century along with consistent measurements to a millionth of an inch. The construction of a surface plate is a physical exercise in algebra. You have to make 3 at once and compare and correct them in a specific order.
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Paul Bicknell
Chris Hayes