开云体育

Tony, does the value of 5V lights fall below 4.5V when you increase the
load to the point that the PSU shuts off? 5V lights is monitored by the
Inverter Control IC U1275. A fraction of the 5V lights voltage is fed into
the BAL Sense input of U1275. I would monitor TP1302 on the rectifier board
and 5V lights. There is also a sense current from T1310 that enters that
Bal sense node and can shut down the PSU.

On page 3-58 of the manual, it discusses the Balance Sense input.

Best,
John

On Thu, Apr 26, 2018 at 12:05 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi JJ:
TP1625 are normal 40V +/-3V ! ( it must be connected to maim unit , it is
related to CRT HV CKT !
If PSU alone , such voltage reading will more positive ( + 130V ) ).
On the other hand , I did measure the value of R1286 and 1287 , it is OK !
When PSU connected to main unit , I do not understand ,for CR1311 and 1312
, I use HSR208 ( 2A 1KV CJ=14pF ) will shut down PSU . but use FR607 ( 6A
1KV CJ= 80pF ) will not shut down the PSU ! both setting are Control
ILLUM must OFF, and GRAT ILLUM are always turn on ( not controllable ! ).
Still finding the problem !
RegardTony CheungAPR 27 2018

From: JJ <jajustin@...>
To: [email protected]
Sent: Wednesday, April 25, 2018 7:04 PM
Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony, did you do the Power Supply test on page 5-8 of the manual : Adjust
Inverter Control R1293 for a meter reading on TP1625 of +40V? Maybe your
operating point for the Inverter Controller is way off. Mine was way off in
the negative range until I adjusted it.

Best,
John

On Tue, Apr 24, 2018 at 10:52 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi John :
It is overall power handling issue for the PSU , U1275 is the controller
for the shut down action, 5V light is NOT only output, there is feedback
to R1304 to controller too !
On the other hand the total current sampling from T1235 to U1275.
I did check C1316, C1317 and C1318 are normal .
My PSU was damaged by miss-align one pin of SENS input on LV Board (

P1483

) :
pin 1 ------- Beam I Sens input on LV board NO Connection.
pin 2 ------- GND Sens input on LV board connected to P83 pin 1
-------Beam I sens. --------------- Beam I sens short to GND.
pin 3 ------- +5V Sens input on LV board connected to P83 pin 2 -------
GND sens, -------------means +5V short to GND !
pin 4 ------- -50V Sens input on LV board connected to P83 pin 3 --------
+5V sens, ------------- short -50V to +5V !
pin 5 ------- +50V Sens input on LV board connected to P83 pin 4 --------
-50V sens -------------- short +50V to -50V
pin 6 -------- -15V Sens input on LV board connected to P83 pin 5

--------

+50V sens ------------- short -15V to +50V
pin 7 ------- +15V Sens input on LV board connected to P83 pin 6 -------
-15V sens ------------ short +15V to -15V

The results is all ( +5V, -50V, +50V, -50V, -15V, +5V and Beam I sens
short to GND ). may be serious damage for the PSU or main unit ?
Anyway it is under repair for the damage !
RegardTony CheungAPR 25 2018



From: JJ <jajustin@...>
To: [email protected]
Sent: Wednesday, April 25, 2018 5:26 AM
Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony,
If all you can draw is 100ma on 5v lights, you could have a problem with
that power supply's pi section filter - I had to change C1318 to get my

PSU

up. It measured 40uf instead of 100uf. That cap may be right on the edge

of

failure at certain loads. There are also 2 other caps in that filter -
C1316, C1317. Note that 5v lights is not regulated on the LV regulator
board - it just goes through the board to the connectors - so the problem
is localized to the cap rectifier board.

I would first change C1318 with any 100uf cap (doesn't have to be

tantalum

to just test). And, do the same sequentially for the other two - swap out
then test. They're pretty easy to change.

Best,
John



On Tue, Apr 24, 2018 at 2:35 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi John :
Yes, I did put it back to 7904 , but find something NOT working !
1. Graticule Light always on ----------- I did check NO -15V at R1451,

but

PSU was tested with full loading pass .2. Front panel push button's

light

not function.3. For Horizontal Mode Switch ALT , CHOP will shut down

the

PSU. A or B is OK !
Regard
Tony Cheung


From: JJ <jajustin@...>
To: [email protected]
Sent: Wednesday, April 25, 2018 1:21 AM
Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony, have you tried putting the PSU back into the mainframe to see if

it

works in its normal load and interaction environment? You may be

chasing

the proverbial wild goose! :)

Best,
John

On Tue, Apr 24, 2018 at 12:16 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi:
It is a good idea ! But I leave my workshop already ! May check day

after

tomorrow. It is midnight in Hong Kong !
One thing I find at least, I disconnect-15 V loads, it become normal.

So

that my next step to check the resistor!
Regard
Tony Cheung


從我的 iPhone 傳送

dadhills@... 於 2018年4月24日 下午11:40 寫道：

Have you checked R1286, 1K, 5%? It is a carbon composition

resistor

and

if it has drifted high in value, it will lower the "total" load

current

limit threshold.

Dave

On Tue, Apr 24, 2018 at 07:59 am, Yiu On Tony C wrote:


Hi Harvey :
My PSU are test alone and connected to Loading resister and "

sens "

return to

LV board.
For the current limiter was controlled by U1275 , and I find the

zener

VR1297

---- 9V are opened , I replace it and now always shut down again ,

even

I open

the zener again , still shut down ! It means cannot return as

before ,

I did

check all the diodes on A12 , but no defective !
There may be something wrong again !
RegardTony CheungAPR 24 2018

From: Harvey White <madyn@...>
To: [email protected]
Sent: Tuesday, April 24, 2018 9:41 PM
Subject: Re: [TekScopes] 7904 Mainframe damaged

On Tue, 24 Apr 2018 13:27:01 +0000 (UTC), you wrote:

Hi :
My 7904 still have problem for PSU !
+/-50V, +/-15V, +5V , +130V are normal with loading power on !
Once I connect the loading to +5V light , it cannot load even

0.1A

!

it will

shut down PSU. ( If normal , It can output up to 3.5A ! )

The diode for +5V lights are defective ( shorted ) and replaced

by

fast

recovery diode FR607 ( junction Cap 80pF )or HER208 ( junction

cap

14pF ).

Sounds as if the supply is working normally for regulation, but

the

shutdown circuitry is too sensitive. There's a current sense

resistor

in there, and some associated parts. Could the current sense

resistor

be too high in value? That will certainly cause this supply to

shut

down on a lower current. I'd also check the amplifier for that

sense,

to make sure it is working properly.

Harvey

I've been working on my 7603 Mainframe oscilloscope and just finished replacing diodes and some caps in the Intensity and Focus DC Restorer sections of the HV board. Here's a link the an earlier message:
/g/TekScopes/message/146928. After parts replacement Intensity and Focus seem pretty good to this newbie's eye :-)

Now, I'm concerned about Q1152 on the Z-Axis board being almost too hot to touch. The PCB in this area is now brown from years of running hot. The Tek # for this transistor is 151-0406-00. I've checked it and its 'brother' Q1132 with one of those inexpensive ZIF component testers and the hFE on Q1152 shows 207 and on Q1132 it's 136. This doesn't match the device's spec sheet, but I'm sure these testers don't correlate to any published values.

From reading over a few similar posts on this group I checked to make sure R1152 measured 3.9K Ohms and verified the base voltage of Q1152 is at 103V. I got the impression Q1152 does run warm to hot normally. Do you think It's OK to swap Q1152 and Q1132 to see if the heat issue follows the components? They are the same part # and operate in almost identical sections, Z-Axis Amp and Auto Focus Amp.

I haven't done much with board except replace R1146 and R1126, the two 1 Watt, 20k Ohm carbon resistors with newer metal film ones elevated a bit to improve heat dissipation. I also replaced the Astigmatism trim pot, R1193, just because it smelled as if it had been 'cooking' for quite some time.

As stated in the earlier post, the LF power supply voltages are 'pretty darn close' to spec. I do not have a way to measure HV at this point.

I have yet to go through checking all components on the board for obvious out of tolerance values. I've been hunting around for a heatsink that will fit, but I don't think I have one handy at the moment.

I look forward to your thoughts on ways to possibly lowering the heat dissipation of this device. I did read that this transistor can be replaced with a 2N5401. This transistor has an epoxy TO-92 case. Heatsinking these transistors is difficult. It seems like using it as a replacement would create more troubles.

Thanks!!

--Al

Hi Craig :
The Cap for 5V light checked O! the may be some short at Front panel interface board ? from the
switch boards shielding !
I may need to disassembly the front panel to clean the switch boards !
RegardTony CheungAPR 27 2018

Not sure I understand that. It is very unlikely that there is a short on the board which mounts the
switches (vertical mode and horizontal mode). Check that the harmonica connectors are plugged in
correctly, and not one pin along in either direction

Craig

I might be able to find a couple of 8056 but I am not sure of their condition. Changing them changed the DC offset and i have no way to check them right now. friend of mine has a tube tester but i won't see him for some time because of circumstances. (we aren't on the outs it is other things)

I also have a few of those HV rectifier tubes, and one GZ whatever, 1,400 volt version.

Not much, mainly pay for packing and shipping, $ 20 total each or add more to one package cheaper. (maybe $ 10 ? maybe less) And I WILL pack them correctly. They would have to really try to break them. Let's put it this way - I got carpet padding and wood.

Basically I might get a six pack of decent beer out of it. I have no online or Paypal so either postal MO or personal (yes really) check.

Hi Craig :
The Cap for 5V light checked O! the may be some short at Front panel interface board ? from the switch boards shielding !
I may need to disassembly the front panel to clean the switch boards !
RegardTony CheungAPR 27 2018

From: Craig Sawyers <c.sawyers@...>
To: [email protected]
Sent: Wednesday, April 25, 2018 10:14 AM
Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony,
If all you can draw is 100ma on 5v lights, you could have a problem with that power supply's pi
section
filter - I had to change C1318 to get my PSU up. It measured 40uf instead of 100uf. That cap may be
right on the edge of failure at certain loads. There are also 2 other caps in that filter - C1316,
C1317.
Note that 5v lights is not regulated on the LV regulator board - it just goes through the board to
the
connectors - so the problem is localized to the cap rectifier board.

I would first change C1318 with any 100uf cap (doesn't have to be tantalum to just test). And, do
the
same sequentially for the other two - swap out then test. They're pretty easy to change.

OK - I've been on vacation in Australia for nearly 3 weeks, and this thread was running before I left!
So I deleted the zillions of mails on this topic, and my comment might well have been already covered.

The 5V lights is sensed by the Inverter Control chip, U1275. It is added to other signals via R1304.
If resistors around that area have changed value, the 5V lights sensing could be trigger happy.

This was probably identified as a problem area, because two different values are in the parts list -
9k31 for pre B181294 and 8k45 after.

Craig

Stanford Research Systems offers a system similar to the Tektronix TM-500/5000 systems. I've not done an exhaustive comparison between what plug-ins SRS offers and what Tektronix offered; I suspect that SRS does not offer as many plug-ins as Tektronix did. But the SRS system is current and modern. The pieces are also expensive.

DaveD

Go to your other thread on this and do the basic checks I mentioned.

Hi JJ:
TP1625 are normal 40V +/-3V ! ( it must be connected to maim unit , it is related to CRT HV CKT !
If PSU alone , such voltage reading will more positive ( + 130V ) ).
On the other hand , I did measure the value of R1286 and 1287 , it is OK !
When PSU connected to main unit , I do not understand ,for CR1311 and 1312 , I use HSR208 ( 2A 1KV CJ=14pF ) will shut down PSU . but use FR607 ( 6A 1KV? CJ= 80pF ) will not shut down the PSU ! both setting are? Control ILLUM must OFF, and GRAT ILLUM are always turn on ( not controllable ! ).
Still finding the problem !?
RegardTony CheungAPR 27 2018

From: JJ <jajustin@...>
To: [email protected]
Sent: Wednesday, April 25, 2018 7:04 PM
Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony, did you do the Power Supply test on page 5-8 of the manual : Adjust
Inverter Control R1293 for a meter reading on TP1625 of +40V? Maybe your
operating point for the Inverter Controller is way off. Mine was way off in
the negative range until I adjusted it.

Best,
John

On Tue, Apr 24, 2018 at 10:52 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi John :
It is overall power handling issue for the PSU , U1275 is the controller
for the shut down action, 5V light is NOT only output,? there is feedback
to R1304 to controller too !
On the other hand the total current sampling from T1235 to U1275.
I did check C1316, C1317 and C1318 are normal .
My PSU was damaged by miss-align one pin of SENS input on LV Board ( P1483
) :
pin 1 ------- Beam I Sens? input on LV board? NO Connection.
pin 2 ------- GND Sens input on LV board connected to P83 pin 1
-------Beam I sens. --------------- Beam I sens short to GND.
pin 3 ------- +5V Sens input on LV board connected to P83 pin 2 -------
GND sens, -------------means +5V short to GND !
pin 4 ------- -50V Sens input on LV board connected to P83 pin 3 --------
? +5V sens, ------------- short -50V to +5V !
pin 5 ------- +50V Sens input on LV board connected to P83 pin 4 --------
-50V sens? -------------- short +50V to -50V
pin 6 -------- -15V Sens input on LV board connected to P83 pin 5 --------
+50V sens ------------- short -15V to +50V
pin 7 ------- +15V Sens input on LV board connected to P83 pin 6 -------
-15V sens? ------------ short +15V to -15V

The results is all ( +5V, -50V, +50V, -50V, -15V, +5V and Beam I sens
short to GND ). may be serious damage for the PSU or main unit ?
Anyway it is under repair for the damage !
RegardTony CheungAPR 25 2018



? ? ? From: JJ <jajustin@...>
? To: [email protected]
? Sent: Wednesday, April 25, 2018 5:26 AM
? Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony,
If all you can draw is 100ma on 5v lights, you could have a problem with
that power supply's pi section filter - I had to change C1318 to get my PSU
up. It measured 40uf instead of 100uf. That cap may be right on the edge of
failure at certain loads. There are also 2 other caps in that filter -
C1316, C1317. Note that 5v lights is not regulated on the LV regulator
board - it just goes through the board to the connectors - so the problem
is localized to the cap rectifier board.

I would first change C1318 with any 100uf cap (doesn't have to be tantalum
to just test). And, do the same sequentially for the other two - swap out
then test. They're pretty easy to change.

Best,
John



On Tue, Apr 24, 2018 at 2:35 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi John :
Yes, I did put it back to 7904 , but find something NOT working !
1. Graticule Light always on ----------- I did check NO -15V at R1451,

but

PSU was tested with full loading pass .2. Front panel push button's light
not function.3. For Horizontal Mode Switch ALT , CHOP will shut down the
PSU. A or B is OK !
Regard
Tony Cheung


? ? ? From: JJ <jajustin@...>
? To: [email protected]
? Sent: Wednesday, April 25, 2018 1:21 AM
? Subject: Re: [TekScopes] 7904 Mainframe damaged

Tony, have you tried putting the PSU back into the mainframe to see if it
works in its normal load and interaction environment? You may be chasing
the proverbial wild goose! :)

Best,
John

On Tue, Apr 24, 2018 at 12:16 PM, Yiu On Tony C via Groups.Io <
tonycheung_hk@...> wrote:

Hi:
It is a good idea ! But I leave my workshop already ! May check day

after

tomorrow. It is midnight in Hong Kong !
One thing I find at least, I disconnect-15 V loads, it become normal.

So

that my next step to check the resistor!
Regard
Tony Cheung


從我的 iPhone 傳送

dadhills@... 於 2018年4月24日 下午11:40 寫道：

Have you checked R1286, 1K, 5%?? It is a carbon composition resistor

and

if it has drifted high in value, it will lower the "total" load current
limit threshold.

Dave

On Tue, Apr 24, 2018 at 07:59 am, Yiu On Tony C wrote:


Hi Harvey :
My PSU are test alone and connected to Loading resister and " sens "

return to

LV board.
For the current limiter was controlled by U1275 , and I find the

zener

VR1297

---- 9V are opened , I replace it and now always shut down again ,

even

I open

the zener again , still shut down ! It means cannot return as

before ,

I did

check all the diodes on A12 , but no defective !
There may be something wrong again !
RegardTony CheungAPR 24 2018

? ? ? From: Harvey White <madyn@...>
To: [email protected]
Sent: Tuesday, April 24, 2018 9:41 PM
Subject: Re: [TekScopes] 7904 Mainframe damaged

On Tue, 24 Apr 2018 13:27:01 +0000 (UTC), you wrote:

Hi :
My 7904 still have problem for PSU !
+/-50V, +/-15V, +5V , +130V are normal with loading power on !
Once I connect the loading to +5V light , it cannot load even 0.1A

!

it will

shut down PSU. (? If normal , It can output up to 3.5A ! )

The diode for +5V lights are defective ( shorted ) and replaced by

fast

recovery diode FR607? ( junction Cap 80pF )or HER208 ( junction cap

14pF ).

Sounds as if the supply is working normally for regulation, but the
shutdown circuitry is too sensitive.? There's a current sense

resistor

in there, and some associated parts.? Could the current sense

resistor

be too high in value?? That will certainly cause this supply to shut
down on a lower current.? I'd also check the amplifier for that

sense,

to make sure it is working properly.

Harvey

On Wed, Apr 25, 2018 at 10:56 am, vaclav_sal wrote:

I would appreciate some assistance to find out why my 464 has this problem.

Now that all these tertiary issues are disposed of (I hope), on to the problem.

First of all let me make some assumptions here -
You know how to use a triggered scope.
You have tried auto trigger, centering, a beam finder if so equipped and none of this resulted in a trace on the screen.

The nature of your question implies you have not worked on alot of scopes. Now,if you turn the horizontal position to the right or left and then turn the vertical position(s) up and down, does a spot appear on the screen ? Sort of "scan" it that way to see if any combination gets you anything on the screen.

If so, that clears the HV circuit. however it still could be blanking, so it is a positive result, but not a negative for anything else.

If you get no spot or trace at any time the first thing to do is to check the HV. This is usually done best at the CRT cathode which is easy to get to at the socket. You'll have to check the manual to see how much voltage should be there and figure out how to measure it if you meter can't, or at the very least find out if it is there.

I you have HV and absolutely nothing on the screen, then check the deflection plate voltages. Those will be connections on the neck of the CRT. The pair on the side should have about the same voltage on them, and the position control should bring them in to very close, do so and leave the control there and check the other pair of plates. they will either be on top or bottom, usually on top, same deal, try to get the voltages close. Within about 3 volts or so should result in at least a spot on the screen somewhere. If not that leaves CRT bias sources or blanking.

This applies to all scopes. Once we get through that I can download the manual. I will wait because even though I have plenty of HD space it is getting hard to find a particular manual because I have so many, all types of test equipment and audio equipment as well, and all mixed up in different directories depending on where I got them. Once I get it I will probably just leave it open minimized for the duration of the thread. I never reboot. (voluntarily anyway)

If you can't measure the HV get the rest of the info anyway and comeon back y'hear !

One more thing - do you have another scope you can use to troubleshoot this one ?

On Thu, 26 Apr 2018 07:22:05 -0700, you wrote:

I'm finally getting around to fixing, updating and working on my 500 plug in collection.
I have a, apparently, rare TM504A chassis that was modified by a previous owner so not all modules work in all slots and sources do not talk to destinations. It also has an oscillation in the power supply that I need to fix (Classic issue with how they did the feedback on the power supply). It is finally time for me to understand the back programing header and how to use it so that say my freq counter can read the oscillator or the volt meter read the power supply though the back plane while still being able to swap out modules.

Mine is a TM504. There's a backplane programming book, and you will
need the manual for each plugin to see what the exported signals are.

I have been unable to find a manual or schematic for this unit, but there are plenty for the TM504. Is there any real difference other than the addition of a fan and switch location? Is the TM504 service manual good enough or if not where can I hunt down a TM504A one?

No idea.

I sure wish there was a modern version of the 500 modules. I have some great modules with no current product options. I use the filter/pre-amp all the time at work and once I updated the op amps it works better than the current version by another vendor. But these things sure are getting old and I wonder if it is worth my time to keep them working for bench work any longer. For now I'll keep trying.

You could update them by re-designing some of the modules and adding
microprocessors. It would be an undertaking, though, so I'd recommend
the TM5000 series if that's a way you want to go.

You'll find that the TM500 modules are decent enough, but as you note,
the technology is old. You can upgrade some of it, but short of
redesigning the entire module, I suspecte your options are limited.

in terms of keeping them working, I'd ask what other similar equipment
you have, and if it's that much better. I have a mixture of
standalone and TM500 modules, each of which has its use.

Harvey

Thanx,
Hawker

What album?

On Thu, Apr 26, 2018 at 07:03 am, Fabio Trevisan wrote:

there's a last problem which I won't be able to solve... the CRT is worn out
:-(

Have you tried boosting the filament voltage ? I have had good luck with that in TVs and now did a scope and it came out fine. It is just a matter of either jumping out a resistor or usually adding a turn to a winding on the HV transformer.

Anyway, back to the topic here. I am pretty adept at boosting CRTs so if you want details contact me, unless you don't want/need to.

Hi,

This is a group, not a forum.

Many members (most?) access this group using the email
function. With that function, messages are emailed to
the member, and display on the member's computer in the
order in which the gods of the internet allowed them to
traverse the internet.... But, not necessarily in the
order in which they appear in the groups.io database.

Further, most members that use the email option, delete,
or move, posts that they have read from their inboxes.

As a result, each message, with a given subject line, has
to be able to stand on its own, or it is just noise.

To help others understand what you are writing about, it
is beneficial to quote some of the post you are addressing.

I see from your email headers, that you posted using the
groups.io website interface to the group.... but alas, with
no quotes...

If you look at the response window on the web interface,
you will see a dialog bubble with a (") in the middle.

If you click on that bubble, the entire message from the
post you are replying to will be pasted into the editor
screen as quoted text.

Trim out any quoted text that doesn't apply to your reply,
but leave enough so that others can tell what you are
replying/commenting to/on, then write your response.

I prefer for the new message to come before the quoted text.

If I can't see your message on the first screen of your
post I prejudge it as not being worth reading and delete
it.

Others prefer scrolling through pages and pages of quoted
text before reading your message... I don't understand that
preference, but then I am not required to.

If you trim out most of the quoted text, it really doesn't
matter which (top post, bottom post) you do, as it will be
mostly on one screen.

Because many new members do not follow the conventions of
this group, it is common for mis-attributions to occur.

This group does not allow attachments. Someone thought
you wanted to attach something, and politely informed that
you can't.

I am sure it wasn't meant to ruffle your feathers...

Usually when you think someone is disrespecting you, it is
best to assume a communication error is happening, and to
let it pass. We have lots of folks from lots of different
cultures, and native languages, here, so 99% of the time you
will be right in that assumption.

-Chuck Harris

vaclav_sal via Groups.Io wrote:

I'm finally getting around to fixing, updating and working on my 500 plug in collection.
I have a, apparently, rare TM504A chassis that was modified by a previous owner so not all modules work in all slots and sources do not talk to destinations. It also has an oscillation in the power supply that I need to fix (Classic issue with how they did the feedback on the power supply). It is finally time for me to understand the back programing header and how to use it so that say my freq counter can read the oscillator or the volt meter read the power supply though the back plane while still being able to swap out modules.

I have been unable to find a manual or schematic for this unit, but there are plenty for the TM504. Is there any real difference other than the addition of a fan and switch location? Is the TM504 service manual good enough or if not where can I hunt down a TM504A one?

I sure wish there was a modern version of the 500 modules. I have some great modules with no current product options. I use the filter/pre-amp all the time at work and once I updated the op amps it works better than the current version by another vendor. But these things sure are getting old and I wonder if it is worth my time to keep them working for bench work any longer. For now I'll keep trying.

Thanx,
Hawker

Hello Vaclav,

Please see my answers just after your questions:
Rgrds,
Fabio

Sorry, perhaps me posting my first one wrong way.

You're welcome... don't need to apologize.

Why is there even a need for attachment?
I did not indicate that in both of my posts.

My mistake... I just assumed there could be a picture because your original message doesn't explain what is the problem that you want help for and because it's so common for newcomers to paste or attach pictures to their first messages.
Since the pictures don't get through to the forum, the messages quite often look like yours, with an open question but without an indication of what the problem is.

I think I am capable carrying on a discussion without pictures - if that was
reason you mentioned attachment.

No bad feelings... One thing you will see in this group is that people from all levels of knowledge (some are really rocket science high level, believe me) and all levels fluency are welcome and treated fairly.
B.T.W. One thing that really *do* annoy many in the group is when people reply to a previous message without quoting the original question or doubt.

Ah... In time, I have myself a 464 that took me about a year to solve all problems... and still there's a last problem which I won't be able to solve... the CRT is worn out :-(

Rgrds,

Fabio

I just uploaded some pictures of the tool.

Mine has the numbers -0755- hand engraved in the handle so the P/N is 003-0755-00.
I added the page from the Tools Catalog to the album.
/H?kan

Sorry, perhaps me posting my first one wrong way.
Why is there even a need for attachment?
I did not indicate that in both of my posts.
I think I am capable carrying on a discussion without pictures - if that was reason you mentioned attachment.

Fabio,

I have looked at the pins you mention on U2232, particularly at pin 12, C1 which is involved in adding zeros. The behaviour of all the pins is consistent with a logic low of around 0.5V and a high level around 3V. The high level has a lot of switching noise looking like analogue ramps with an amplitude of close to 1V and the low level is clean but of very short duration so that you may not see it depending on your sweep speed and trigger settings. The narrow spikes carry the readout information and move and disappear when you change eg from 500mV to 1V per division, the 'noise' on the high logic level is largely unchanged.

Have you tried removing U2232 (and maybe U2244 and U2185 the row and column decoders) and cleaning pins? You may have the notorious TC IC sockets which are very prone to corrosion problems.

Regards,

Roger

Hi Albert,
There are a good few on eBay.co.uk.
Most are in Germany which should be handy for you..
Plenty in the States as well.
Regards
jim
Ei2BB

Used to have some many years ago.?Will check just in case any are still in the drawer but pretty sure I sold mine to someone on eBay.
www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."

On Thursday, 26 April 2018, 09:18:14 BST, Albert Otten <aodiversen@...> wrote:

>

? ? Does anyone have any data on Nuvistors (miniature metal-envelope
tubes), or have any to sell?? I could use an 8056, and have some
7586s...

A useful site is Frank's Electron tube Pages, and its mirrors.
The 8056 pdf for instance via :
.

Albert