Author Topic: Tektronix 2465B oscilloscope teardown  (Read 455279 times)

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Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #500 on: August 14, 2015, 01:44:32 pm »
Those Adafruit adapters are so nice to use...

The CTT Cal is pretty painless, as the manual mentions, set the sweep to 10nSec, V/div at 200mV, and then you need to supply a 1 Volt .5uSec pulse centered about 0 Volts (no offset), and triggered externally by the timing generator set for 1uSec markers. the onscreen prompts are fairly easy to follow. I am stating all this from memory,  :-/Oso excuse any errors, corrections to follow later, if any.
The CTT Options Service manual explains it...   oh here it is...
 

Offline ehsmeng

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Re: Tektronix 2465B oscilloscope teardown
« Reply #501 on: August 14, 2015, 07:59:47 pm »
Thanks a thousand times for this teardown. It just helped me fix a moving damaged 2465a.
 

Offline timb

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Tektronix 2465B oscilloscope teardown
« Reply #502 on: August 24, 2015, 09:58:53 pm »
So, over the weekend I finally got my $80 eBay Calibration Special back together and working!



At some point this spring I picked up a TM 503 Power Module, PG 506 Cal Gen, TG 501 Time Mark Gen and SG 503 Leveled Sinewave Generator on eBay for $80. All the units had yearly cal stickers up to 2013. At first the units were behaving erratically, which turned out to be a power supply issue. $20 in capacitors and a new bridge rectifier in the power module solved that problem. After fully disassembling and cleaning all three units, I just needed to lube some switches, reseat all the ICs, replace some 74 Series logic and now everything works perfectly. Well, except the fast rise board in the PG 506; I broke one of the BNC connectors off the board when I over-torqued the nut. I'm trying to find a suitable pair of end launch BNC connectors to replace them with.

Anyway, it's amazing what you can find on eBay with a bit of patience and some luck. Hopefully I can get my scope calibrated this week, just waiting on some attenuators now.





Oh, I also modded the TM 503 a bit. It was a stock unit without the rear BNC/DB-50 option; but I found out the steel frame actually has the holes for the BNCs and cutout for the DB-50, they just put a cover plate on without the holes! So, I added BNC connectors, in case I need them, and also added an IEC power connector where the DB-50 would have gone. Since the built-in push-pull switch was wonky, I opted to replace it with a bog standard toggle switch in the hole that the hard-wired power cord formerly occupied. I'm really pleased with how it came out.




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« Last Edit: August 24, 2015, 10:02:24 pm by timb »
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Offline j ferguson

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Re: Tektronix 2465B oscilloscope teardown
« Reply #503 on: September 13, 2015, 10:38:11 pm »
Has anyone here actually entered calibration data recorded from the scope Exer 02 display onto a generic NVRAM file ( to correct its calibration data for your scope) and successfully used the new chip?  Part of this question involves relating data addressing on the new file as shown on a typical hex editor. 

 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #504 on: October 07, 2015, 06:50:40 am »
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Offline mtdoc

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Re: Tektronix 2465B oscilloscope teardown
« Reply #505 on: October 08, 2015, 09:56:18 am »
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #506 on: October 08, 2015, 09:57:05 am »
Sweet, that'll work. Thanks!


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Offline med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #507 on: October 10, 2015, 01:06:46 pm »
Since this has turned into a thread about Tek 24XX scopes in general I figured I'd join the fray with my recently acquired 2465 DMS. It was a business write off and  I managed to get it for free.

I've used many Tek scopes in the past but I wasn't familiar with this series. Upon power up I was greeted with a screeching fan and an error code of CT Test 81 Fail 02. I solved the fan issue with some lube on the motor shaft.  I started searching the net for manuals and found them for the mainframe as well as the options. And stumbled upon the Tek Yahoo group and joined up.

One of the first things I learned with these 24XX scopes before doing any troubleshooting is to verify all the supply voltages (This is true with any old equipment but seems to be really emphasized with this series). I was lucky in this respect. All the supply voltages are in spec and no caps have been changed. But I know the day will come where I'll have to pull the supply and inverter boards and re-cap them. That won't be an easy task with this fully optioned 2465 DMS.

CT Test 81 Fail 02 is a calibration fail with the Counter/Trigger option. According to the manual a Tek PG 502 Pulse Generator and a Tek TG 501 Time Mark Generator are required for calibration. I'm just a hobbyist and I don't have this equipment. But I do have a Heathkit IG-4244 Oscilloscope Calibrator that is capable of generating a very precise 1 MHZ square wave. With the help of the Yahoo group, a BNC tee, a 2X attenuator, and a DC supply to insure proper offset the Buffer board accepted the signal and performed a successful cal and cleared the error. See 1 MHZ photo.

After clearing the CT fail the scope passed all kernel and confidence tests, at least for a while. It is now getting a BU Test F1 Fail 10 on an intermittent basis which is a buffer board EAROM checksum fail. I need to investigate this further but the consensus is leaning towards a bad EAROM chip. For now I'm bypassing the error and the mainframe and counter appear to be working properly. See BU fail photo.

The DMM option is a total train wreck. The DCV spec'ed accuracy is 0.03%. Not even close. Example: with my 1.000 VDC standard it reads 0.9886 V on autorange. If I go up one range it reads 1.000 V. The kernel/confidence tests do not check the DMM cal directly other than basic functions. The service manual states to perform a cal if you suspect an issue. I did do some extensive resistance checking of the input networks just in case something was fried and found nothing. Proper calibration of the DMM option requires a Fluke 5101 with calibration constants ranging from .19 V to 450 V. As I stated before I'm just a hobbyist and there is no way I'm going to be able to get a Fluke 5101. I don't really consider this function important anyway since I have a Fluke 87 and a Fluke 8021B that take care of my needs. See DMM1 and 2 photos.

The A5 Control Board in a 2465 is pin thru hole, not SMD as in 2465A and B. It is not as prone to damage from leaking caps as many have discovered with the SMD board. Also, the 2465 uses EAROM's to store it's cal data and doesn't require a battery. See A5 photo.

The DMM board swings over or can be completely removed to gain access to the buffer board and supply/invertor boards. See DMM board photos.

Thanks for reading. Input/comments always welcome.   

                 
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Offline j ferguson

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Re: Tektronix 2465B oscilloscope teardown
« Reply #508 on: October 10, 2015, 08:00:53 pm »
Has anyone here actually entered calibration data recorded from the scope Exer 02 display onto a generic NVRAM file ( to correct its calibration data for your scope) and successfully used the new chip?  Part of this question involves relating data addressing on the new file as shown on a typical hex editor.

Sparky was kind enough to share both a dump of the NVRAM on his 2445b and a video of the EXER (02) output taken from the screen prior to removal of the old Dallas NVRAM.  I stepped through the display a word at a time and copied down all 256 of the "words".  He was right, each word is comprised of two characters and the first one at 00h address in the EXER (02) sequence is written to 001Eh on the chip itself, second character to 001Fh and so forth. 

The data on his video and the data in the NVRAM dump starting at 001E agreed exactly.

 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #509 on: October 11, 2015, 01:12:17 am »
If anyone in the VA/NC area needs a scope cal, I've got a calibrated PG506, SG503 and TG501 to do it with. You just need to bring your scope over.

You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.


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Offline soren

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Re: Tektronix 2465B oscilloscope teardown
« Reply #510 on: October 11, 2015, 01:58:41 am »
You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.

Calibration depends on the 10V trimmer in the power supply and the DAC reference trimmer on the A5 board.

Removing the A1 board is also rather fiddly.
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #511 on: October 11, 2015, 02:03:07 am »
Ah yeah, forgot about the DAC reference. It's a shame a scope's calibration involves so many factors; it would have been cool if they could have made a "Calibration Module" that you could pull/swap out, sort of like the HP 3455A DVMs.


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Online BravoV

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Re: Tektronix 2465B oscilloscope teardown
« Reply #512 on: October 11, 2015, 06:50:53 am »
...<snip>...  I managed to get it for free.

I hate you. LOL ...j/k  >:D

Congrats on the score.  :clap:  :-+

Offline med6753

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Re: Tektronix 2465B oscilloscope teardown
« Reply #513 on: October 11, 2015, 01:28:21 pm »
...<snip>...  I managed to get it for free.

I hate you. LOL ...j/k  >:D

Congrats on the score.  :clap:  :-+

Please don't hate me.   :-[   I was definitely in the right place at the right time.

But if I manage to find someone who has a Fluke 5101 AND they let me borrow it for a few hours THEN you can hate me.  :P
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Offline SoundTech-LG

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Re: Tektronix 2465B oscilloscope teardown
« Reply #514 on: October 12, 2015, 01:29:25 am »
If anyone in the VA/NC area needs a scope cal, I've got a calibrated PG506, SG503 and TG501 to do it with. You just need to bring your scope over.

You know, I wonder if it would be possible to take the main A1 board out of a 2465X, put it in another scope, do the cal and then move the board and NVRAM back to the original scope. That should work, right? As all the analog stuff is there. If so, that could make it a lot easier for people without the equipment to get their unit calibrated, as you wouldn't need to ship the whole scope back and forth, just the main board. Hmmm.


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The gains and electrode physical placement differences in each CRT will make that very questionable. At the very least H, and V gain, will quite likely need adjustment to compensate for each CRT. Most likely more.
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #515 on: October 12, 2015, 03:15:37 am »
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw

Link doesn’t work for me. Says I’m not logged in, despite being logged in.
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Offline mtdoc

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Re: Tektronix 2465B oscilloscope teardown
« Reply #516 on: October 12, 2015, 04:55:24 am »
Anyone have the Digi-Key parts list handy for a power supply re-cap?


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Here's the file posted to the Yahoo Tek scope forum. Mouser and Newark part no.s only though.

https://dl-web.dropbox.com/get/_2465LVPS_ReCap%2C%20A1%20recap-parts.xls?_subject_uid=315056499&w=AABBEwsyvXv8-MkXuvQXylKApXyus6nBmOsuJ0r-fgUkYw

Link doesn’t work for me. Says I’m not logged in, despite being logged in.

That's weird. I'm new to DropBox. Let's try again. Try this:

https://www.dropbox.com/s/fvqo6oj8ktbm2pj/_2465lvps_recap%2C%20a1%20recap-parts.xls?dl=0
 

Online BravoV

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Re: Tektronix 2465B oscilloscope teardown
« Reply #517 on: October 12, 2015, 05:02:31 am »
Why not just zip it and attach here, it will be useful reference for others in the future, sorry , don't have dropbox account.

Offline mtdoc

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Re: Tektronix 2465B oscilloscope teardown
« Reply #518 on: October 12, 2015, 05:13:16 am »
Why not just zip it and attach here, it will be useful reference for others in the future, sorry , don't have dropbox account.

Well doh!  I didn't realize you could attach zip files here. Here it is:
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #519 on: October 14, 2015, 07:32:00 pm »
Thanks, I made an order with Digi-Key. Though, I screwed up one part! Instead of three 1uF caps I ordered 10uF! I looked at the schematic, and it appears they're used in the Op Amp feedback path that goes to the inverter feedback. (C1274, C1291 and C1292)

I'm wondering if it's okay to use them? Normally it's okay to increase a cap's size when it's just for filtering, but when it's for an op amp's feedback I'm just not sure.


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Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #520 on: October 16, 2015, 08:14:14 pm »
Hurf durf, disregard last post. Upon looking at the caps in question, they are bi-polar electrolytics. Which, thinking about it, makes the schematic make much more sense!

I happened to have two new 1uF Nichicon BP caps in my parts drawer (thanks to Radio Shack going belly up). They're axial instead of radial, but I made it work. I went ahead and replaced the two that belong to the 10V ref circuit and just put back the original 1uF cap that belongs to the +5D circuit, as it tested OK. I figure the reference is the most critical so I might as well refresh those caps.


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Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #521 on: October 16, 2015, 09:39:59 pm »
Hmm, okay, new problem! I just noticed that according to the schematic C1132 is a 10uF 160V part and C1115 is 250uF 20V; however, on my board with the original Tektronix caps, it's the opposite (according to the layout diagram).

As I removed the original caps, I wrote down the values on a printout of the layout, so that's how I put them back. I'm going to assume the layout sheet has the numbers wrong and what's labeled C1132 is actually C1115. I feel this is a safe assumption, but I wanted to double check before I make an ass-umption of myself. ;)








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Offline MarkL

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Re: Tektronix 2465B oscilloscope teardown
« Reply #522 on: October 16, 2015, 10:42:02 pm »
Follow the traces to see which one is connected to CR1132.  That has to be the higher voltage cap.
 

Offline timb

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Re: Tektronix 2465B oscilloscope teardown
« Reply #523 on: October 16, 2015, 10:43:30 pm »
Unless CR1132 is marked wrong too! XD


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Offline MarkL

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Re: Tektronix 2465B oscilloscope teardown
« Reply #524 on: October 16, 2015, 10:51:10 pm »
Well, trace as much as you need to satisfy your uncertainty.

The same side of CR1132 also goes to P223, pin 5.

Conversely, the other capacitor in question goes to P234, pin 4, and also L1115.  And the other side is ground.  That should be an easy giveaway.
 


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