开云体育

Roy,
Generally, it's best to troubleshoot a problem and solve it.

BUT, in THIS case, what we have here, thanks to all the efforts of these capable and experienced techs here, is that ALL the problems have ALREADY been "Troubleshot", and condensed into ONE bunch of tasks to do now. These problems and defects are now "KNOWN".

So, why try to reinvent the wheel, when somebody else has already travelled the road down which you want to walk, and solved the problem which you have now?

That is the concept of SOLVING "KNOWN" defects, and that is the rationale behind the Recapping exercise (which in the case of my kit, includes not only capacitors, but resistors as well)!

Those capacitor problems of c. 1999 which you mentioned have NOT gone away - there is NO SHORTAGE of Chinese capacitors made in 2025, which still fail in the same way as those 26 years ago, and understanding the Chinese mindset of "profit at any cost", we can expect the no-name and counterfeit components to continue to fail in the future. It's got nothing to do with anti-Chinese prejudice - it's simply the way that China does business.

Therefore the choice of BRAND and Model is very important, far more important than the cost.

And if the tech who does the work is sloppy and unprofessional, then of course the chances of his damaging the PCB and causing catastrophic failure are present and real, and it makes no difference whether he replaces one cap or 50 caps.
By the same token, a thoroughly professional tech will have 100% success, whether he replaces one cap or 50.

Generally most of the techs who are active in this forum have extremely high professional work standards and technique, and can be trusted to do work with 100% success rate.

"Learn from the mistakes of others, because you will not live long enough to solve them all yourself"

Menahem

Ironic that the tek logo looks a bit coarsely digitised for an analog scope

The aging process for 157-0125-00 is documented on page 36 of the tube aging pdf on tekwiki.



It’s also mentioned on page 110 in the tube specification list which shows the tek part numbers of the raw tubes they would have used and later reassign the part number to the selected one



Nothing about specific brand names but still interesting info if you haven’t seen those documents

It's great you've submitted this information here. I'm sure this will help
some folks down the line. Way to go.

On Sat, Apr 12, 2025 at 6:51?PM rich.meyer@... via groups.io
<rich.meyer@...> wrote:

The Tektronix 155-0124-00 is a hard part to find. I was able to repair my
2235 scope with an alternate part. I used a Tektronix 234-1008-20 which
was made by Maxim for Tektronix. The Military version of the 2235 was the
AN/USM488. The Military National Stock Number (NSN) for this part was
5962-01-062-7562, which is also the 234-1008-20. I located this part on
eBay, replaced it, and got my 2235 operational again.

The Tektronix 155-0124-00 is a hard part to find. I was able to repair my 2235 scope with an alternate part. I used a Tektronix 234-1008-20 which was made by Maxim for Tektronix. The Military version of the 2235 was the AN/USM488. The Military National Stock Number (NSN) for this part was 5962-01-062-7562, which is also the 234-1008-20. I located this part on eBay, replaced it, and got my 2235 operational again.

Jim,

I had gotten some of those very tubes in the 1990s. I didn't use them until I (tried) to calibrate my 547 a few years ago and found them a little less than wonderful than actual 6DJ8s to the point that I wondered if they were even related to 6DJ8s. They didn't always work well in place of 6DJ8s. I hope you have better luck with yours.

(As I have only 1A1 plug-ins, I can't help you with the chassis rods.)

All gone, looks like I missed out again.

I recently bought a 3B3 via ebay, that I got cheap because it had been damaged. The only obvious damage was that one of the long, round, chrome plated chassis rods was badly bent. I thought I had some good, salvaged, 3-series rods so I figured this might be an easy fix.

First surprise: I don't find any chassis rods in my stash of Tek spares. I managed to straighten this one. It's not bad, but if someone has a good one they'd like to part with, I'll pay a reasonable price for one. Note that the 3-series chassis spacing rods are ~12-3/16" long, longer than the 1 or Letter series rods. This is a late rod, with the crimped hex at one end.

Second surprise: One of the 6DJ8s has the getter turned completely white. It had been knocked sideways by whatever had bent the rod, so I figured there must be a crack around one of the base pins, which had been bent. No such cracks appeared, but I finally noticed that the pinch tip at the top of the tube had been completely broken off. Sad, but at least I have a few spare 6DJ8s.

However, this dead 6DJ8 is unusual. There is no etched ID anywhere. In typical red ink, it says NATIONAL, with the National logo, then the Tek part number, 157-0125-00, then MADE IN JAPAN. Oddly, 6DJ8 does not appear anywhere.

The 157-0125-00 is an aged and selected version of the 6DJ8. So, with the Tek part number inked onto the glass envelop, the ageing and selecting must have been done in Japan, by the original manufacturer. Or perhaps they were able to control their production carefully enough to make the ageing and selecting unnecessary. I'd love to know how this was done.

Or maybe this was done so late in Tek history that no one cared. There are some additional numbers in red ink on the tube: 51A, 83781, and 8729. The last one might be a date code.

So, at some point in time (1987?) Tek contracted with Richardson Electronics, in the Chicago area, to make 157-0125-00s (6DJ8s) for them, with the National label on them. Then Richardson turned around and subcontracted them to Japan (Toshiba, Matsushita, Hitachi?) to make the actual tube. I have to assume that this was all done with Tek's approval, but it still seems odd, especially with no 6DJ8 marking. This was probably a very nice tube, and probably still is, except for being full of air and the consequently blown getter.

Have you ever seen a National, or any other brand, tube with the 9 digit Tek part number printed right on it?

--
Jim Adney
Madison, WI USA

Hi,
Sorry for this old story but there's some news about my TDS520.
Due to real life it waited since december 2023 for my attention. Last week only took it from its shelf, opened it and I removed the nearly 50 chemical caps on the acq board (A10).
Then A10 went in a friend's dishwasher. I then recapped with Nichicon and put it back. Remember it booted in 2023 and only failed on Acquisition & Attn/Acq interface. Now no boot.
I measured on the new caps and found one supposed +5V to be -0.6V. To make it short there's a through hole just near C1584 and of course it juiced there and now no more continuity. I soldered a small piece of wire and got back that 5V.
But still no boot and no 1kHz on the probe comp signal.
I followed the troubleshooting procedure which told me to "Change A12". Well, thanks but no. That procedure had me disconnect some connectors though and once reconnected the scope booted.
-Fail processor (pass in 2023)
-Pass acquisition (fail in 2023)
-Fail Attn/acq (as in 2023)

There I got myself a little snack away from the darn thing. Came back two hours later and rebooted
Now Fail processor and all the rest pass.
And : "Consult service manual for fault isolation. Press CLEAR MENU to continue" which I did but not with much hope.
I was wrong. I put a probe on CH1 and got the probe comp signal on screen.
I did not proceed recapping A11 (processor) because it booted and I wanted to test A10 first. Now I will.
Also I should "Consult service manual for fault isolation" ! There's still that Fail processor.

Here I am and, as usual, all criticism, comments or advices welcome.
Best
Renaud

SG 503, often needs main frequency range C'AM switches fixed.

Requires special Tek cable for cal into 50 ohms

SG504 needs à leveling head

PG 506 rare and costly, see epay. Often needs repair or cal
PG506A can be $700..2000 see epay

The TM 5000 mainframe takes a 3-4 wide CG5110 that combines the functions of all the TM 500 plugins for cal

Bon chance

J

Hi,

I got one !!!!

Only four left now

Regards, Joe
Joe
Germany

I did some more measurements and there is indeed some ripple on the LV PSU. The worst of it is on the 130V and the 15V rails. The 5V rail which powers the area of the circuit that 'appears' to be problematic is marginal. I'm contemplating replacing all of the caps in the LV while I have it apart.

I scored a TM503 with a TG501 and SG503 and would love to add a 506A to have nice calibration set. Send me a message and let me know! Thx. I'm in NJ.

Hi John! Staying busy. 17 of the 25 demo boards in this batch have sold since I made the post early this afternoon, so I'll need to build more soon.

All proceeds support the VintageTEK Museum.

-Thomas

I am still waiting for some advice.
In the mean time I checked for poor connection solder joints.
Clean the A4 timing board.

On Sun, Mar 30, 2025, 8:42 AM Saroj Pradhan via groups.io <sarojman.Pradhan=
[email protected]> wrote:

I was working on 2230 which has power supply failure.
Changing the main bridge rectifiers CR901... CR904, Q9070 and Cr907
restored the power supply. The scope power ons with an issue CDT issue CDT
value changes from 73 to 77 during different sessions of power on.

After pushing the one of the menu scrolling key CDT goes off.
I have following display issue:
1. No trace
2. Readout tex for volt/div and sec/div display.
3. Intensity and focus works
4. Sec/div switch in A mod doesn't work.
I can see only 50m 5ns and. 2s changing the position of switch.
5. Horizontal position switch works but only for half portion of the
screen.
What I did so far.
1 since there is no trace just a dot I started to
Look for horizontal section.
2 looked for ramp signal at waveform 24 and 29 but I could not see any
just a dc offset.
3 decided to clean the sec/div switch so according to the instruction I
pulled out A4 board which contains sec/div switch. In the A4 boaed I found
strange connection. Collectors of q742 and q732 are tied together and
connected to A sweep input of U760 while B sweep input is left floating.
I will be thankful if some one in this forum suggest on this issue and
guide me to resolve the issue of my scope.
Thanks
Saroj

Hi Thomas. Long time. How are you? Thanks for the link.

New eBay link:



-Thomas

On Wed, Apr 9, 2025 at 11:53 AM, Giuseppe Marullo[iw2jww] wrote:

RECAPPING
Of course, if I have someone to recalibrate it, I may well think of
recalibrating it AFTER recapping.

I'm very interested in the topic of 'recapping.'
I know there was a problem with some brands of electrolytic capacitors, coming from China, circa 1999... and that has an effect on those things manufactured that used them... mostly from China.
Yet...IME... what I have seen is more damage to the PCB, then good.

What's the motivation for ordering a capacitor 'kit'... and doing 'shotgun' replacement of capacitors?

IMO... if one does not take the time to test... for a bad component... and then to identify, and specify the appropriate component....
Well how do you know, you are not replacing something, with something that is worse?
Also... but importantly, using inappropriate de-soldering, and soldering tools, and supplies, risks damage to the pcb... which might not be trivial.

--
Roy Thistle

If you have an A or B series, you can get the calibration values back in the NVRAM with this utility (or with GPIB, if you have the equipment):

/g/TekScopes/files/24xxAB-writecal-1.1.zip

The only way to get them back into a 2445/2465 (plain) that I know of at the moment is via the optional GPIB interface (OPT 10). A similar utility to the above for A/B versions could be developed for 2445/2465 scopes, but ER1400 failures are far and few between (unlike dead batteries), and virtually no one has backed up their 2445/2465 cal data so it can be used with such a utility. If you have a backup of your cal data and are trying to get it back in the ER1400, please speak up!

The above zip archive has demonstration code in ./related/earom.c on how the Tek "spiral add" checksum algorithm works on the 2445/2465, plus how parity is calculated for the range of locations that include parity. So, you might be able to determine the offending entry by putting your EXER 02 data in the code.

If you want to post your 2465 EXER 02 data, we could also look at it together in this thread.

Theoretically, you could force the scope to recalculate the checksum by performing a calibration step, such as CAL 04, where you don't actually modify anything and then exit the cal procedure. I haven't tried this, but keep in mind if you do you're ignoring bad cal data that could affect the scope's operation.

From a reliable source, I am told there is an undocumented screen utility similar to EXER 02 for *entering* the data, but the person I spoke to can't recall how it was done. More work with a better logic analyzer (which I have now), and/or analysis with Siggi's 2465 Ghidra image and 2465 MAME simulator may find the answer. It's on my to-do list.

-mark

Hello Paul
thanks for the info I have just ceck the 100 Mhz oscillator but thats up and running ?
any other problems to check ?
best regards
Hubert