Date   

Re: Newbie with a 466 that won't sweep

Andreas Ragner
 

Hi Richard,
I checked my notes and found the following:

" Tektronix 466 Repair (October 2013):
466 early model, Timing circuit board A7, signal 'A' SWP START LEVEL to Q1002A
C1115 shorted (Tantal, 100µF/20V), replaced by AL-Electrolytic 220µF/35V "

Symptom of the 466 was no horizontal sweep, but vertical deflection was ok.
I chose the capacitor just by looking for a most close value fit in my new parts box.
The solder side of the A7 board is reachable only by dismantling.
As I did not plan to carry the scope around in a car (i.e. no shaking and rattling),
I made the repair process straightforward. The tantalum has been cut just at the body.
I soldered the capacitor to the remaining standoffs.

Regards, Andreas


Re: tek 2215 trace position issues

nanovnauser@...
 

I currently have the crt removed,is it ok to power the cope on with the crt removed,or do i need to connect the anode eht to prevent arcing?


Re: 465B recapping and tantalum caps

pdxareaid
 

On Sat, Oct 23, 2021 at 11:02 AM, Ozan wrote:


It looks like there are two alternate locations for the thermistor.
yep, i see that now. odd but REALLY resolved now. thanks, phil


Re: 465B recapping and tantalum caps

Ozan
 

On Sat, Oct 23, 2021 at 10:12 AM, pdxareaid wrote:


On Sat, Oct 23, 2021 at 10:00 AM, pdxareaid wrote:


"The mysterious cap you mention is a 50 ohm thermistor in parallel with the
27
ohm resistor."

thanks Mark. I have seen no documentation of that thermistor. How do you
know
this? Where can i look? Did i just miss something simple?
Ahhh...i see it now in the circuit diagram. it is just not depicted on the A4
board for some reason. Thanks.
-------

It is RT4373, on A4 board diagram it is shown to the left of R4373 trimpot. In your picture if you look at the same location there are two empty solder islands, instead the thermistor is in the "mystery component" location. Tracing connection in the picture shows it is parallel to R4374 (27-ohm) which matches the schematic. It looks like there are two alternate locations for the thermistor.

Ozan


Re: 465B recapping and tantalum caps

pdxareaid
 

On Sat, Oct 23, 2021 at 10:00 AM, pdxareaid wrote:


"The mysterious cap you mention is a 50 ohm thermistor in parallel with the 27
ohm resistor."

thanks Mark. I have seen no documentation of that thermistor. How do you know
this? Where can i look? Did i just miss something simple?
Ahhh...i see it now in the circuit diagram. it is just not depicted on the A4 board for some reason. Thanks.


Re: 465B recapping and tantalum caps

pdxareaid
 

On Sat, Oct 23, 2021 at 08:00 AM, Mark Vincent wrote:


C4331 is 47mfd. It should be 25V or 35V. Using a larger value, 100mfd 25V ULD
for example, will work.
I agree the V rating should be higher. even 25V seems a little low but 35+ is likely sufficient.


Re: 465B recapping and tantalum caps

pdxareaid
 

"The mysterious cap you mention is a 50 ohm thermistor in parallel with the 27 ohm resistor."

thanks Mark. I have seen no documentation of that thermistor. How do you know this? Where can i look? Did i just miss something simple?


TDS784C early serial number firmware?

Jared Cabot
 

Hi all,
I'm currently running firmware 5.2e on my TDS784C scope, but I've heard there is a version 5.3(x) floating around.
Does anyone have a copy of this firmware, or have a scope with this version that they can dump it from via GPIB? (I can provide the simple commands to do so).
Or even any versions that aren't on tekwiki, we may as well post them up there for future reference.

https://w140.com/tekwiki/wiki/TDS784

Thanks!


Re: TM500 tester switch - Attn. Jared Cabot.

Jared Cabot
 

Hi,

I had the pins and sticker supplied with the switch when I purchased it. Maybe they forgot to include them with the switch when packing them?
All you really need is a two short bits of wire to stick in the holes as shown in the manual to limit the rotation. I think some tinned copper wire, piano wire or even a bit of paperclip could work if it fits.
Some cello-tape would work fine to replace the sticker I think.

Jared


Re: 465B recapping and tantalum caps

Mark Vincent
 

C4331 is 47mfd. It should be 25V or 35V. Using a larger value, 100mfd 25V ULD for example, will work.

The mysterious cap you mention is a 50 ohm thermistor in parallel with the 27 ohm resistor.

Mark


TM500 tester switch - Attn. Jared Cabot.

Colin Herbert
 

Hi Jared,

I have now (eventually) got what all of the parts for this tester seem to
be. I am however a bit puzzled about the Grayhill switch. Mine doesn't seem
to have anything other than the switch, internal tooth lockwasher and
mounting nut present. I see that you used a set of limiter pins and a foil
sticker to retain them, but these items do not appear with my switch. Such
pins and sticker do not appear on the DigiKey list either, as far as I can
see. Did you actually use the proper Grayhill items and do DigiKey stock
them? If not, how might I go about getting the switch to correctly be a
4-pole, 6-turn switch?

Colin.


Re: 465B recapping and tantalum caps

n4buq
 

I do still have some of those boards available.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "pdxareaid via groups.io" <mousterious=yahoo.com@groups.io>
To: "tekscopes" <TekScopes@groups.io>
Sent: Saturday, October 23, 2021 4:29:14 AM
Subject: [TekScopes] 465B recapping and tantalum caps
Greetings 465/465B repairers and recappers.
I have just spent time with a couple of broken 465B's and thought I'd pass along
the experience.

1. Recapping low PS
I recapped the low power supplies and used the ebay discs to install snap-in
caps. https://www.ebay.com/itm/273254508468
I now regret having used those discs.
After I ordered the discs, I noticed a TekScopes member "n4buq" had a much
better solution (bravo!) and may still in fact
offer his standoff board for sale. If not, it could be made with a low tech
copper-clad hole board, resist pen and etch acid.
With that solution, everything is easily accessible.
I did, in fact, break one trace, not discovering it until after the new
discs/caps were installed.
Even though I did a continuity check to avoid exactly this, I think I damaged
the trace when doing some minor work nearby just before cap installation.
I had to jump the trace off the board for a fix. I could have easily fixed it
on the A4 board if I had used his standoff board solution.
n4buq writeup
https://groups.io/g/TekScopes/files/Replacing%20Electrolytic%20Filter%20Capacitors%20in%20a%20Tektronix%20465.pdf

2. Tantalum Caps
Years ago I put together an HTML file identifying the dipped tantalum caps that
tend to fail so often.
I lost access to it in the Yahoo/GroupsIO move but that has been fixed recently.
I have uploaded an updated HTML file with the following addition (as well as
updated contact info):
C4331 47uF 20V with a note. It is a confusing one. Should it be a tant or a
film cap? Read the note.
The file is https://groups.io/g/TekScopes/files/465Btants.html

3. Mysterious Cap
While I was scratching my head over 2. above, I notice a tiny dipped tant on
all three of my (early build) A4 boards. I had missed it in the original
survey. I tried to look it up in the manual (ARTEK early build 465B) but it is
not there. The pads are there but the tant does not show up.
I looked for an add/delete change in the manual but did not see any appropriate.
I think it is a filter cap in the horizonal amplifier circuitry but it is not in
the diagram either.
It physically sits between R4373 and R4374 on the A4 board. The pads are even
on the manual's A4 diagram, but no cap.
If that thing shorts, it is going to be one confusing debug.
Here is a pic of it https://groups.io/g/TekScopes/photo/269282/3324900
Does anyone know what is going on here? Can anyone identify this cap and point
to Tek documentation?



465B recapping and tantalum caps

pdxareaid
 

Greetings 465/465B repairers and recappers.
I have just spent time with a couple of broken 465B's and thought I'd pass along the experience.

1. Recapping low PS
I recapped the low power supplies and used the ebay discs to install snap-in caps. https://www.ebay.com/itm/273254508468
I now regret having used those discs.
After I ordered the discs, I noticed a TekScopes member "n4buq" had a much better solution (bravo!) and may still in fact
offer his standoff board for sale. If not, it could be made with a low tech copper-clad hole board, resist pen and etch acid.
With that solution, everything is easily accessible.
I did, in fact, break one trace, not discovering it until after the new discs/caps were installed.
Even though I did a continuity check to avoid exactly this, I think I damaged the trace when doing some minor work nearby just before cap installation.
I had to jump the trace off the board for a fix. I could have easily fixed it on the A4 board if I had used his standoff board solution.
n4buq writeup https://groups.io/g/TekScopes/files/Replacing%20Electrolytic%20Filter%20Capacitors%20in%20a%20Tektronix%20465.pdf

2. Tantalum Caps
Years ago I put together an HTML file identifying the dipped tantalum caps that tend to fail so often.
I lost access to it in the Yahoo/GroupsIO move but that has been fixed recently.
I have uploaded an updated HTML file with the following addition (as well as updated contact info):
C4331 47uF 20V with a note. It is a confusing one. Should it be a tant or a film cap? Read the note.
The file is https://groups.io/g/TekScopes/files/465Btants.html

3. Mysterious Cap
While I was scratching my head over 2. above, I notice a tiny dipped tant on all three of my (early build) A4 boards. I had missed it in the original
survey. I tried to look it up in the manual (ARTEK early build 465B) but it is not there. The pads are there but the tant does not show up.
I looked for an add/delete change in the manual but did not see any appropriate.
I think it is a filter cap in the horizonal amplifier circuitry but it is not in the diagram either.
It physically sits between R4373 and R4374 on the A4 board. The pads are even on the manual's A4 diagram, but no cap.
If that thing shorts, it is going to be one confusing debug.
Here is a pic of it https://groups.io/g/TekScopes/photo/269282/3324900
Does anyone know what is going on here? Can anyone identify this cap and point to Tek documentation?


TDS500/600/700 option parts wanted

Jared Cabot
 

Hi all,

I recently acquired a TDS784C scope and I'm interested in adding the HDD and video trigger options. Also an early serial number 2M (8M memory) option board too.
If anyone has these parts available, or can pull them from an old scope, I'm interested in purchasing them (and pay for shipping to Japan).

Thanks!
Jared.


Re: Tek 1503C: Display backlight issues

 

Bruce,

Replacing the backlight is apparently easy. Here is an entire thread discussing the topic https://groups.io/g/TekScopes/topic/83184585#183313

The web interface for Groups.io provides an excellent search feature, and this thread is the only hit for “1503 backlight” https://groups.io/g/TekScopes/search?q=1503+backlight

— Jeff Dutky


7B92 no sweep

Bruce Atwood
 

7B92, S/N B052568, No Sweep, Help!

Since it has been almost a year since my 7B92 arrived in my new-to-me 7904 I’ve decided that it is time to make it work.

Test setup
‘92 installed in right-most slot of a 7603. No vertical plug-ins installed. (The 7603 has been tested with a 7B53A in the right-most slot and a 7A26 in the left-most slot.) The side covers have been removed from the ‘92. The side covers are removed from the 7603 giving good access to the main trigger board and the sweep board.
The external trigger is driven by the cal-out of a 7904 set to 1kHz and 0.4 volts. The termination is off. Trigger is set to Auto, DC coupling, External. The “Alt” and “Level” controls are pushed in. Sweep speed set to 20 usec/division. The “Triggered” light is off when powered-up but come on and stays on if single-sweep is selected.

U310 Voltages, taken with Fluke 115, Waveforms observed with 7409/7A26/7B53A combo:
Pin # name Voltage
1. +TD input 1.159
2. -TD input 0.232
3. + TD Auto 0.331
4. - TD Auto 4.890
5. -5V -4.980
6. Auto timing 0.022
7. Trgd Lamp 4.602
8. HO timing 2.239 + Hold-Off ramp, ~4V P-P, 40 usec
9. 0.001
10. HO out 0.289 + 0.5 usec 6V pulses at HO frequency (25kHz)
11. SS ready 4.663
12. 0.013
13. 0.216
14. Reset timing 4.716
15. Reset start 0.762
16. 0.074
17. SWP disable 1.686
18. Lockout input -0.006
19. Auto Mode 0.001
20. +5V 4.889
And:
TP 392 4.367V
TP 321 1.429V
C 1.61V + Hold-off pulses
E 0.115V + Hold-off pulses
CR740 (TD) ~1.5uSec, ~600mv pulses at Hold-Off ramp frequency
Q754 base 0.747V
Q748 base 0.790V


Re: TEK 475: Dead on Start Up.

pdxareaid
 

coincidentally but apropos, on a 465B, i just had a film cap fail that was apparently used by a previous owner to replace a failed tantalum filter cap. he used the same voltage rating.
it was rated 20V in a 15V circuit. i will replace with either a tant or film of same capacitance but at a higher voltage rating.


Tek 1503C: Display backlight issues

Bruce Lane
 

Fellow Tekkies,

I'm on the tail end of my annual run to the Bay Area, and one of my acquisitions is a Tek 1503C TDR. The unit's in outstanding electrical/cosmetic condition, and even has a good battery pack. Only problem is, the display backlight has gone out.

From what I've already found, online, this particular instrument uses EL paneling for the backlight. I can probably replace or repair what's in there, but I'm wondering if anyone's experimented with any other kind of repair/retrofit (LEDs, perhaps?)

In either case -- Repair suggestions and sources for parts would be appreciated. Thanks much!


Re: TEK 475: Dead on Start Up.

Michael W. Lynch
 

Although I have never used film caps myself, I would think that they would be a good alternative to tantalum caps. Much better than aluminum electrolytics, for sure.

--
Michael Lynch
Dardanelle, AR


Re: TEK 475: Dead on Start Up.

Mark Vincent
 

Martin,

Replacing tantalums with film is fine. I have replaced a lot of the axial types that are 1mfd and lower with film. The radial types I also replaced with film. The originals were high ESR. One place that a film replaces a tantalum is the 2400 series. These have three 4,7mfd tantalums that go bad. I have not had any problems with a film replacement. Using film to replace lower value electrolytics works well. Places where I have done it is the crt bias filter, on the primary of the oscillator of the 7000 series power supplies (the 1 and 2mfd electrolytics) and other places. The Wimas you mentioned are great. I have used these. I have used the Kemet R82 series with the suffix DQ60J. These are the long lead types in 5% tolerance. Advantages of film are they are not polarized and will dry out. I measured a new 1mfd tantalum and film. The film was "0" (not literally/shorted) ohms on my meter while the tantalum was several ohms. I have an analogue ESR meter.

Using a higher value tantalum to replace a decoupling tantalum is fine. For example, using a 10-22mfd to replace a 6.8mfd. For areas where the value is for a frequency determining or filter, use the same value, higher voltage is fine. So far using a 25V tantalum on a 15V line has not failed. It is operating 60% of the rated voltage. Paralleling a tantalum with a low ESR electrolytic can be done to get lower ESR and higher capacitance.

Mark

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