Author Topic: Tektronix 2465B oscilloscope teardown  (Read 469284 times)

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Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1400 on: January 06, 2019, 09:56:59 am »


FWIW, none of the 3 2465s I own have that ribbed plastic/rubber/vinyl what-the-fuggever-it-is on the bottom front, though the suggestion that it serves to prevent occlusion of that most important vent over the U800 certainly sounds plausible. Possibly some vendor-added spacer for a 2465 that was assembled into/made part of a larger, special-purpose test gear?

mnem
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I disagree. I think it's a factory piece for all of them. My 2465 DMS came from a small electronics device placement facility in Colorado. As mentioned before my other 2465 came from IBM in New York. Tggzz said he has at least 2 with the piece and he's in the UK. I suspect it's easily damaged or the adhesive gives way and it falls off and is not reinstalled.
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Offline mnementh

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1401 on: January 06, 2019, 04:17:53 pm »
Hmmm... possibly a poorly documented/undocumented late-production revision then?

You'd think with a sample of 3, one of mine would have SOME evidence of that belonging there; at least some adhesive residue. In all honesty... an afterthought peel-n-stick bumper really doesn't feel like Tektronix to me.

mnem
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Offline mnementh

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1402 on: January 06, 2019, 05:45:38 pm »
If there was a TSB for U800 and it's mounting it apparently wasn't known outside Tektronix. And as a side light how come no one, other than that one individual, produced one with that mod?

One of my 2465's was owned by IBM. IBM was very diligent about insuring their test equipment was up to snuff and had it's own instrument labs who's sole responsibility was repair/calibration. Only "tuff nuts" or unable to fix equipment was sent back to Tek which didn't happen very often. The U800 in this 2465 is untouched and the scope would have been back to the instrument lab on a yearly basis for a minimum a calibration. So I'm questioning the validity of this "TSB". IBM has bought literally thousands of instruments from Tek over the past 60 years so my thought in the interest of customer support this "TSB" would have been published and available.

And as another side light the last IBM internal instrument lab was disbanded about 2006 or so and all instrument repairs/calibrations are now contracted to outside cal labs.

Sorry... "TSB" was the wrong term. I'll blame multiple-discipline terminology cross-contamination. ;)  I guess Tek would have called it a "Service procedure" or "Service revision" or something similar.

As I can confirm after just now leafing through EVERY PAGE of my March '85 Version 2465 Service Manual, while Tek provided mind-numbingly detailed documentation regarding the electronic engineering and theory of operation on their 'scopes, mechanical service procedures are glaringly short on detail if not completely absent, particularly where specific unique components are concerned. I would not be surprised that if these procedures were not released outside of their own shop; once upon a time service was as much or more of what Tek offered as the product itself, so such knowledge would be their stock-in-trade.

Short version: I recall a discussion in one of the 2465 threads; I thought it was here somewhere, but more likely on Anatek or alt.sci.repair:

A user posted complaint that he had sent his 'scope in to Tek for repair after a U800 failure, and when they returned it, it had only one nut on the IC. He was furious that Tek service had been so careless. Some discussion ensued, consensus was that Tek knew what they were doing and it was probably supposed to be that way. A week or so later, he posts a followup including quotes from an eMail from his tech at Tek, with reference to a Tek document number outlining the change to only one nut on the IC flange with reduced torque specification as a revision to the service procedure to prevent recurrence of the U800 failure.  In retrospect, it is possible this reference was ONLY for cases where U800 had failed, and they replaced it at Tek.

Of course at this point I can only offer my recollection; so this is all 3rd-party hearsay. I assumed this was common knowledge by now; not a point of contention.  :-//

My ex-NASA 2465 has only that one nut on U800, and I have no intention of replacing the other. My personal opinion is that handling the chip in any way is likelier to cause failure at this point than any reliability gain that might be come from re-mounting.

Cheers,

mnem
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« Last Edit: January 06, 2019, 05:50:11 pm by mnementh »
 

Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1403 on: January 06, 2019, 08:47:47 pm »
I knew what you meant by "TSB". TSB = Service Bulletin.
 
Does your nut less U800 also have that heat sink and warning label?

I think the best advice we can give anyone concerning U800 is two fold....

1. Make sure the fan and cooling system is in good shape (Dust free, etc)

2. Leave U800 the hell alone unless you have an issue. It's been in there +30 years and worked fine, despite the funky engineering.
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Offline mnementh

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1404 on: January 06, 2019, 11:19:21 pm »
"TSB" indicates it was something they would actively broadcast. I'm not sure I believe that was the case. So, still wrong term in this context.  :-[

No, as I said, that pic is of a mod done based on that "Service revision"; not of any 'scope I know was handled by Tek. I just didn't feel like digging mine out of storage, taking it apart, then putting it back together again for a pic.

And add another point; this was also part of the discussion I recalled that service revision from:

3. Don't run your 24xx for too long without the cover on. Without it in place, the fan doesn't pull any air across U800.

mnem
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Offline N3SWR

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1405 on: January 13, 2019, 11:27:54 pm »
Gentlemen,

There's too many of you to list that have helped me get my 2465B back up and running again.   So a big thanks to the community and all other involved.

In summary, I went through the supply re-cap which actually was fun.  The A5 board - well not so fun, but a learning experience somewhat.  I've been around good commercial equipment
for most of my career and each manufacturer is different the way they explain things in their service manuals.  Keep that in mind for a moment.

So, having removed the old Dallas RAM and swapped in a new RAMTRON, all seemed fine for the most part.  I went through the DAC ref voltage saga where the 10K resistor was open
only to be left with a screen full of dots and crazy aberrations haunting me through the cal procedure.  I had to stop - nothing made sense on screen.
Swapping out the Z-axis hybrid was no help - I had a bunch to play with just to be sure it wasn't that hybrid, and it wasn't.  It ended up being the grid bias turned way up by some one before me.

So with the scope back up and running and looking good for a change I did a cal.  So here's my question...

When you're done with the cal and scope is powered on still, is THAT THE TIME to return the jumper back to the no cal state?  Or, do you turn the scope off after completely done, THEN return the jumper to the no cal position?

I did while the scope was on - only to be greeted with a Fail 04 test 10 failure after re-powering the scope.  In essence, there was a checksum error. 

After that, I reloaded another set of cal data onto the RAM (for testing) and didn't touch the jumper (it was in the no cal position).  The scope works fine now.

My problem is in understanding just what they mean in the manual - when to move that jumper specifically.

So can anyone spell it out in no uncertain terms so I don't have to revisit the checksum error once again.  That's a long procedure. only to loose the data in the end....

Thanks guys and keep up the great work you all are doing!!
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Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1406 on: January 13, 2019, 11:54:01 pm »
Power off, then move the jumper back to the "No Cal" position. Power up and you should be OK.  :-+
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Offline N3SWR

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1407 on: January 14, 2019, 12:45:13 am »
I thought that was my error.  Sucks getting old...   :palm:    But at least we have cool equipment to keep our minds busy!

Thanks  :-+
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Online Miti

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1408 on: January 19, 2019, 05:12:39 pm »
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.
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Online tggzzz

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1409 on: January 19, 2019, 06:02:38 pm »
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that?

Mental arithmetic and knowing what I'm probing :)
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online Miti

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1410 on: January 19, 2019, 08:35:38 pm »
Mental arithmetic and knowing what I'm probing :)

Are you saying that you are an engineer and you're not lazy enough not to do mental arithmetic? Come on, you're bragging... ;)
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Offline mnementh

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1411 on: January 19, 2019, 09:46:42 pm »
That's actually pretty clever.  :-+ If you substitute some GP spring contacts scavenged from an old PC motherboard or card edge connector, and solder them to the copper rings, you might be able to improve reliability.

mnem
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Offline jonpaul

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Tektronix 2465B CTT OPT 06 CT TEST 81 Fail 03 OUT OF LIMITS?
« Reply #1412 on: February 08, 2019, 03:02:46 pm »
Hello all:  I am struggling with both models to do a CAL.

Result form normal 2465/7B A5 board problem:

Failed NVRAM Dallas Semi battery, replace with new part, program with default parameters, place new NVRAM on low profile socket.

And removed and replaced all SMD lytics that leaked on the boards, repaired damages.

NEW Issue on 2465B CTT :  CT TEST 81 Fail 03

Using  TEK cal procedure with  1V pk sw wave at 1.00 MHz, to CH 1,

I consistently get  FREQ OUT OF LIMITS message.

I verified the input signal is fine.

Is there an internal clock CAL step? I am just doing this part of the CAL not the entire procedure.

I have the CAL/NO CAL jumper  on A5 board in CAL position.


Any assistance is appreciated!

Many thanks

Jon PAUL

Jon Paul
 

Online med6753

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Re: Tektronix 2465B CTT OPT 06 CT TEST 81 Fail 03 OUT OF LIMITS?
« Reply #1413 on: February 08, 2019, 03:27:32 pm »
Hello all:  I am struggling with both models to do a CAL.

Result form normal 2465/7B A5 board problem:

Failed NVRAM Dallas Semi battery, replace with new part, program with default parameters, place new NVRAM on low profile socket.

And removed and replaced all SMD lytics that leaked on the boards, repaired damages.

NEW Issue on 2465B CTT :  CT TEST 81 Fail 03

Using  TEK cal procedure with  1V pk sw wave at 1.00 MHz, to CH 1,

I consistently get  FREQ OUT OF LIMITS message.

I verified the input signal is fine.

Is there an internal clock CAL step? I am just doing this part of the CAL not the entire procedure.

I have the CAL/NO CAL jumper  on A5 board in CAL position.


Any assistance is appreciated!

Many thanks

Jon PAUL

I can help. I have calibrated the Counter successfully. First, the square wave MUST be 1MHz within 10Hz or so. Verify it with a frequency counter. 2nd, the signal source must have a rise time of at least 1 ns or less. If it's more it may not take. And 3rd...and really important....the square wave must be more or less equal crossing the center line or 0. If it's all negative going or all positive going it will not take the cal.

Hopefully this helps...it should. But if you still have issues post back. 
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Offline jonpaul

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1414 on: February 08, 2019, 05:16:50 pm »
Hello there:

WOW PERFECT, the instructions seem to just specify a 1 uS period and 500 nS 1V pk sq wave, used TM501 time mark gen >>trig pulse gen.

Forgot to center the crossing on middle div!

Also: I can not locate the SERV manual or Adjustment for 2465B CTT opt 06, only for 2465B, and 2465 CTT.

Does it exist? Any differences in the adj procedure? May have to do a full CAL anyway, but hope a partial on just CTT will get it running without the failure errors.

MANY THANKS AGAIN!

Jon Paul
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Offline AMR Labs

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1415 on: February 08, 2019, 05:56:23 pm »
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.

Not ideal, but when in need to use a non-readout pin 10x probe just making a mental note to multiply the readout by a factor of 10 works for me. So basically 100mV/DIV really is 1V/DIV, and so on. After all its not like this is going to affect the calibration of the scope or anything similar. Just the On-screen V/DIV -scale readout- will be wrong. Problem is in the middle of a procedure while my brain is concentrating on something more important, or I get distracted, sometimes I do forget.

Not suggesting you did not know this already, but your question seems to point a bit in the direction that the scope always needs to be told when using a 10x probe in order to stay accurate, or perhaps I just misunderstood your question.
« Last Edit: February 08, 2019, 06:00:56 pm by AMR Labs »
 

Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1416 on: February 08, 2019, 11:03:40 pm »

Also: I can not locate the SERV manual or Adjustment for 2465B CTT opt 06, only for 2465B, and 2465 CTT.

Does it exist? Any differences in the adj procedure? May have to do a full CAL anyway, but hope a partial on just CTT will get it running without the failure errors.

MANY THANKS AGAIN!

Jon Paul

Couldn't tell you about the service manual for the 2565B. I have a 2465 and the procedure is covered under the 2465 Option 06 and 09 Service Manual. Now I would ASSUME that the Counter cal procedure is the same across the 2465, 2465A, and 2465B but you know what happens when you assume.   :palm:
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Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1417 on: February 08, 2019, 11:12:54 pm »
Also, see this post within this thread.......

https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg1937605/#msg1937605

I had forgotten that I posted this.  :-DD
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Online Miti

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1418 on: February 09, 2019, 02:19:21 am »
I have a question about the coding rings on the Tek 24xx series. If you don't use probes with coding pin, your scale factor is wrong. How do you mitigate that? Do you just ignore it? I use a small interposer ring with a 10K 0402 resistor on the edge and a springy ring on top, but it is not always reliable.

Not ideal, but when in need to use a non-readout pin 10x probe just making a mental note to multiply the readout by a factor of 10 works for me. So basically 100mV/DIV really is 1V/DIV, and so on. After all its not like this is going to affect the calibration of the scope or anything similar. Just the On-screen V/DIV -scale readout- will be wrong. Problem is in the middle of a procedure while my brain is concentrating on something more important, or I get distracted, sometimes I do forget.

Not suggesting you did not know this already, but your question seems to point a bit in the direction that the scope always needs to be told when using a 10x probe in order to stay accurate, or perhaps I just misunderstood your question.

No, I'm not saying that the scope is not accurate, is just that the readout is wrong and is about not using a feature that is there just because they didn't add a simple feature to manually select the scale factor.
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Offline AMR Labs

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1419 on: February 09, 2019, 02:47:39 am »
Agree, a manual override for the readout pin sensor would have been useful. Strange Tektronix never though one would use a conventional probe without that pin, even tough quite a bit of the Tek probes don't have them.
 

Offline jonpaul

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Tektronix 2465B oscilloscope teardown
« Reply #1420 on: February 11, 2019, 01:09:47 pm »
Hello  med6753, many thanks for your help!

Big Progress here:  :)

a/ CAL: Your tips re the CTT CAL procedure signal were perfect, I used the TM501 to generate the 1.000000 MHz and  trusty PG502 250 MHz pulse gen to make a +0.5 ..-0.5V 5 uS fast rise squarewave. Freq exact ~ 1 HZ with DC508.

After centering transition and DC, cal CTT proceedure FINALLY worked, no "out of range". 
(note, with good NVRAM data and just CTT needing CAL, failing CAL CTT returns scope to the NVRAM error test 04 fail 10)

The HOR CAL seems OK but CH1 and CH 2 vertical are off 3..5% so VERT CAL is next.
Any tips in that procedure, (have PG506)? Even if other functions CAL seem OK, should I still do a full CAL?

b/  old issue:  This 2465B CTT op 06 (SN 066xxx) is  losing the panel settings at next turn on and default to 50 mv/DIV AC coupling etc regardless of previous settings.  :( I believe that this symptom existed before the old NV RAM failed and was replaced. Besides CAL data does the NVRAM also get FP settings written at shutdown?  Since NV RAM is new and works and the scope seems to initialize and shutdown normally, what can cause this symptom?

c/ Misc cleanup:

A5 board options connector J4241 mates to the option ribbon cable with 2 connectors on the A5 end and 2 more with greater separation on options end. That links A5 to CTT options board. At A5,  The second connector and thick cable loop interferes with the NVRAM as the machine pin socket raises it a bit. Any reason not to just cutoff the unused connectors?

The Fan is a bit noisy, replacement is the NIDEC Beta SL?  Many models exist, as fan is critical to cooling, have 12V 0.12 and 12V 0.16 A models. Any tips on best replacement part?

Usual dead graticule lamps, any pitfalls in replacing? Suggest the original incandescent lamps or try LEDs?

d/ Finally if anyone has a 2465B Options manual for sale or swap or the PDF I will appreciate, as I am missing that from my huge TEK manual library.

Enjoy,

Jon


PS: Going thru this repair and rejuvenation, I can only marvel at the electronic, mechanical and software design of the most marvelous and last CRT scope from TEK!
Jon Paul
 

Offline Satbeginner

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1421 on: February 11, 2019, 01:20:49 pm »
Hi,

I have the option manual in pdf, will see if I can upload it.
Don't know how to upload 25Mb, so I put it in a DropBox, here is the link to it:

https://www.dropbox.com/s/7dgbqmnusf0ki5e/2465A_2467_070-5857-00_Options_Manual_Jun87.pdf?dl=0

Stay tuned,

Leo

« Last Edit: February 11, 2019, 01:24:33 pm by Satbeginner »
You need a scope to repair a scope, and you need many multimeters to repair another multimeter!
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Online med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1422 on: February 11, 2019, 01:40:07 pm »
JonPaul....good deal, glad I could help!  :-+

As far as your other issues are concerned.....I have a 2465 (no suffix) and my experience is limited to that model. I have no experience with the 2465B. There's quite a few differences between the 2 models. But I'm sure MarkL will see this thread and I'm quite positive he'll be able to help.  :-+ 
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Offline jonpaul

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1423 on: February 11, 2019, 01:57:12 pm »
Satbeginner Leo: Many thanks but that manual seems to cover only 2445A, 2465A and 2467 but not 2465B or 2467B!

Perhaps you have those?

Jon
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Offline Satbeginner

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Re: Tektronix 2465B oscilloscope teardown
« Reply #1424 on: February 11, 2019, 02:30:21 pm »
As far as I know, the options are the same, and no, don't have anything else...

I used it on my 2465B's and 2465 ADM without problems.
You need a scope to repair a scope, and you need many multimeters to repair another multimeter!
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