Author Topic: Restoration glory of Keithley 2001 DMM  (Read 194541 times)

0 Members and 2 Guests are viewing this topic.

Offline mimmus78

  • Supporter
  • ****
  • Posts: 650
  • Country: it
Re: Restoration glory of Keithley 2001 DMM
« Reply #50 on: January 09, 2014, 09:33:35 am »
After watching all those horror images I tear down my K2001 dating to late 1996 to check caps. They are VZ(M) too :-(

They are not bulging now, wondering if is better to change it or leave everything like is now.

I found a circuit patch at q550 (watch next photo) anyone know why is there?



For you all feticists of ADC I include some photos of my board. Don't know if it can help somewhere:






 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #51 on: January 09, 2014, 10:45:34 am »
Your unit prolly fixed that issue, but I would change then just in case. caps not getting better with age :]

Thanks for good pics. Your ADC have custom ASIC or factory remarked CPLD, that's interesting.

Can you make more photos of analog board parts and maybe one overall shot of digital board? Also if u have time and programmer , read firmware from ROM chip?

Ill check that signal bypass of yours tonight, be sure. That is control signal for one of mux gates. How its connected on Q550? Hard too see on photo.

UPDATE:

Added part of ohms source. Sorry, that's all i have so far.. That Q550 is NFET, according to 2001 repair manual, and none of my boards have it. It definately switches U323 and related to ohms function. Maybe just a fix for dead gate, dunno.
Would enjoy more photos like this, for sure, as your meter is newest from members over here, so far  O0

ADC schematics pretty much finished, unless some mistakes, so now my interest is analog board..
« Last Edit: January 10, 2014, 04:41:39 am by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #52 on: January 11, 2014, 04:50:28 am »
I'm still alive :)

Continue for some schematics reversing.

Redone mains input 110/230V selection circuitry and frequency detect. Based on Rev J, as Rev L have some little differences, will update later.

PDF

Refreshed isolation components on analog board, added External trigger and DONE BNC outputs.

PDF

Little update for ohms/amps circuitry (hate this unit, hard to trace).

PDF

Added temporary block diagram into schematics, as opening repair manual PDF not convenient..:

PDF

Total wasted today - 6 hours  :)
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #53 on: January 11, 2014, 07:18:25 am »
I followed this discussion for some time and I want to repair my 2001 to. Can somebody help me and give advice? My 2001 is working and I didn't notice anything strange. When I run the automatic self test I see some errors. Sometime there are only these errors:
407.1
407.2
407.3
408.6
409.6
410.1

but a few times it also showed error codes starting from 303.2.
The unit is not calibrated for ~ 10 years can this als cause self-test errors?

Any advice where to start?
 

Offline KJDS

  • Super Contributor
  • ***
  • Posts: 2441
  • Country: gb
    • my website holding page
Re: Restoration glory of Keithley 2001 DMM
« Reply #54 on: January 11, 2014, 07:25:25 am »
I followed this discussion for some time and I want to repair my 2001 to. Can somebody help me and give advice? My 2001 is working and I didn't notice anything strange. When I run the automatic self test I see some errors. Sometime there are only these errors:
407.1
407.2
407.3
408.6
409.6
410.1

but a few times it also showed error codes starting from 303.2.
The unit is not calibrated for ~ 10 years can this als cause self-test errors?

Any advice where to start?

The best place would be to look in the service manual and add the names of those error codes to your post.

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #55 on: January 11, 2014, 08:25:35 am »
Thanks KJDS,

I found the following errors:

Front End:
407.1   2V Range
407.2   200V Range
407.3   750V Range

/200 Correction Factor:
408.6   Signal Comparisons

/750 Correction Factor:
409.6   Signal Comparisons

Converter:
410.1   TRMS Converter


And after a new cold start I just got another long list of additional codes I did not all noted down but it started at:

Input Path:
303.2   Open Circuit Ohms and Ohms Protection
etc.
 

Offline KJDS

  • Super Contributor
  • ***
  • Posts: 2441
  • Country: gb
    • my website holding page
Re: Restoration glory of Keithley 2001 DMM
« Reply #56 on: January 11, 2014, 10:14:31 am »
It sounds like there's so much wrong that I'll guess it's a power supply issue. Take the lid off and check all the rails.

Offline mimmus78

  • Supporter
  • ****
  • Posts: 650
  • Country: it
Re: Restoration glory of Keithley 2001 DMM
« Reply #57 on: January 11, 2014, 11:04:57 am »
Sorry I'd been busy ...

Here you the hi res photo of analog and digital board.

http://imageshack.com/a/img19/8351/3isw.jpg

http://imageshack.com/a/img18/222/1lnq.jpg

I'd prefer to add links because the images are very big.

Unfortunately the analog board is out of focus, I realized this when the meter was again on the shelf ... so in next days I will tear down again to take a new photo.

And this is how the patch on Q550 is done:



I seems sort of AND port? Still have to check schematics posted here ...

 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #58 on: January 11, 2014, 11:10:11 am »
jan86, welcome, tear it down and make photos for us. Check electrolytes as first measure, you can see my post above. Those four near transformer are related to front end.

Make close visual inspection, if any borked components, or dirt on pcb anywhere.

Calibration is not cause of errors, as I have two units able to pass selftest over and over with cal date 1993 and 1994. :)

« Last Edit: January 11, 2014, 11:14:00 am by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #59 on: January 12, 2014, 10:14:51 pm »
Thanks for advice. I still need to get familiar to this instruments repair manual. I know there are different test points and ground. As a quick check I hooked up an oscilloscope to the ground bold of the plastic cover and the supply check points behind the display. I found the following voltages:

+5V = +4.88
+15V= +15.06
-15V= -14.99
-8VF= -7 and -8 (jumps very short to one voltage and back to the other approximately every second)
+8VF= +6.2 and +7.2 (jumps very short to one voltage and back to the other approximately every second)

Is this normal or is this caused by wrong reference ground?
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #60 on: January 12, 2014, 11:09:55 pm »
So far so good.

Can you take photos of your hardware? Overall shot of analog and digital boards, and closeup's of analog board top areas.

+8vf/-8vf jumping is okay, that's some dynamic signal i did not figure purpose out yet.
I show correct signals in this post.
Check if yours match. This is 2w ohms 200kohm range, normal speed, 6.5 digit.

Check Q543 (it's near TRMS AD637 area), is it getting hot?
Also make sure your C114,C115,C116,C117,C101,C104,C108 capacitors are okay and did not leak anything under them.

I attached PDF schematic part for BS-/BS+ and power curcuitry, you can measure those test points if you have them on PCB..

Make sure not short anything, these pesky circuits are sensetive.

Btw, if anyone get in touch regarding K2001 - i'm online on skype - tin_topmods :)
Working on schematics pretty much every day last few weeks.
« Last Edit: January 12, 2014, 11:13:30 pm by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #61 on: January 13, 2014, 04:52:44 am »
I can later make pictures when I have camera. I noticed that the +8vf/-8vf signals change depending on the mode the instrument is in  (I didn't check in detail). Q543 is not warm like all other components are low temperature and can easily be touched by hand. The BS voltages are 38V

No leaking capacitors and the instruments looks like it is brand new made in 2002. It seems to be working fine and if I didn't run the test mode I never new something is wrong. Sometimes many errors are gone. Is there really something wrong?

The cal seal is gone is this a problem or can the cal button be pushed?

PS: I must say I can hardly work on this project due to a lack of time so it can be that I will respond with a delay
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #62 on: January 13, 2014, 05:43:34 am »
Seem you have newest meter, compared all stuff we have here. Would be really interesting to see which Rev is yours?

Quote
Sometimes many errors are gone.
Is it after warmup? I mean do you have selftest errors if just power-on cold meter, but they gone after it run 30 or so mins?
It can be dirt on PCB, which conducts current somewhere on analog board, but I'd hold off cleaning for now, as improper cleaning
can make it totally worse, as analog board is very sensitive for leakage. I have one PCB which have random errors, and plan to
debug it next week, so maybe then can help you for more specific diagnostics.

Quote
The cal seal is gone is this a problem or can the cal button be pushed?
No problem, cal button just unlocks calibration mode in main menu (Comprehensive calibration, manual PDF), in which meter will ask
you to provide precision voltages and resistances to it's input to perform self-cal.

I would not suggest doing so, unless your source is Fluke 5720A or similar grade calibration source.
If you send meter to calibration lab, they don't care if there is seal present or not :)

Tomorrow I'll send one of my K2001's (which i got pass self-test anytime everytime if powered on 110VAC mains) and K2400, will see
how it goes...

On chinese bbs some guy posted docprint corner of K2001 schematics, it's marked Rev R.

While mine analog boards are Rev L and Rev J.
You can find revision letter in analog board corner, near rear inputs fuse.

Mine: 2001-102-04L. 04 means layer, it's 4-layer PCB, so it's marked on every layer.



Quote
I must say I can hardly work on this project due to a lack of time so it can be that I will respond with a delay
No problems, take your time. Even while quick response is cool, we all here sharing just for fun, we still have stuff and work to do  8)

Interesting note:

I did some testing with variable input voltages (mains) using Chroma 61504 AC source (2KVA)

AC input settings: 90VAC, 132VAC, 180VAC, 250VAC - 50Hz - meter failed self-test with 200.1,200.6,200.7,201.2 (but still able to do measurements)
AC input settings: 90VAC, 132VAC, 180VAC, 250VAC - 60Hz - meter pass self-test without any errors, on all input voltages.
AC input settings: 90VAC, 132VAC, 180VAC - 400Hz - meter failed self-test with 200.1,200.2,200.6,200.7,201.2,401.1 (but still able to do measurements)
AC input settings: 250VAC - 400Hz - meter failed self-test with 200.1,200.6,200.7,201.2 (but still able to do measurements)

Something is screwy on that auto-selection input circuitry maybe...
« Last Edit: January 13, 2014, 05:56:46 am by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #63 on: January 13, 2014, 07:15:05 am »
the revision is p

I noticed it very often failed test after the click of the big white mechanical relay (k503?) near the big yellow capacitor. Maybe a coincidence. In cold condition it first failed earlier and now after warm-up with less errors.

I think it is still to early the draw a conclusion due to the low number of tests I did.

Is it possible some tuning in the instrument is not correct but just at the edge of pass/ fail?

I can also check what will happen if I hookup a variable transformer to change the mains voltage a little bit.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #64 on: January 13, 2014, 07:20:48 am »
Cool, Rev P :D

I wonder, how many revisions they did in 20 years for 2001's PCB, if assuming one letter one revision is correct :D
Not like modern hardware development, revision 0 -> revision -> 1 -> EOL -> scrap :D

Different behavious on my unit was with change of mains frequency, not voltage. Except 250VAC level, all other voltage variances led to same result (I tried only 90,132,180 and 220,250VAC, as those are within meter specs).

When you perform self-test, you have nothing connected to meter inputs, correct?

Was meter used heavily since 2002, if you know? Maybe just faulty relay contacts.
Can you list errors in every conditions (worst case, and usual case after warmup) ?

Today's progress:

A/D buffer, gains, PDF
« Last Edit: January 13, 2014, 07:40:47 am by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #65 on: January 14, 2014, 05:40:45 am »
Today I noticed something strange. When I set the instrument to 2w resistance measurement with manual range to 1GOhm and execute the test mode then I measure 0.1 GOhm. When I change range down and up it disappears. During this strange value that drifts slowly up I cannot measure resistance and it only starts to measure resistance when I toggle range.

bad relay?
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #66 on: January 14, 2014, 01:10:48 pm »
Hm, or solid-state switch (there are plently of DG211's there for ranges/function switches).
Let me check my meters later to see if they do similar :)
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline jan86

  • Contributor
  • Posts: 7
Re: Restoration glory of Keithley 2001 DMM
« Reply #67 on: January 15, 2014, 08:06:39 am »
I can confirm other 2001 instruments have the same issue/ bug.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #68 on: January 16, 2014, 05:53:47 pm »
What about upgrade Model 2001 with new parts? :)

 >:D
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #69 on: January 17, 2014, 09:46:37 pm »
In case anyone want jump in and join K2001 endavours, there is one with issues for sale on bay :)
eBay auction: #151210943549
Made in 1997

5 days to go.
« Last Edit: January 17, 2014, 09:48:17 pm by TiN »
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #70 on: January 24, 2014, 12:00:14 am »
Gone for $573 :) Hope it got into good hands.

Meanwhile, started design for new VREF to install in one of K2001's.

LTZ1000ACH with LT1112ACN8, +15V single-rail supply, VPG Z202 resistors (will try to order them).
Schematics attached.

Thinking maybe R3,R6 and R5,R4 could be better to try get VPG resistor network, as this is best way to have tempco same, thus keep ratio constant?
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Offline KJDS

  • Super Contributor
  • ***
  • Posts: 2441
  • Country: gb
    • my website holding page
Re: Restoration glory of Keithley 2001 DMM
« Reply #71 on: January 24, 2014, 12:15:06 am »
Does the K2991 use the same resistor network as the K2000? If so I may be able to find some spares.

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #72 on: January 24, 2014, 12:37:57 am »
No, not that I have on my revisions (maybe later one have it). Only K2002 shares TF255 with K2000.
But this is for another daughter board to replace LM199/399 to LTZ1000A , DIY stuff, so i'll try get VPG resistors (first will check cost)
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #73 on: February 07, 2014, 02:05:22 pm »
Well, time to bring some little life in this abandoned thread.

Got an update, first unit sent for Tek cal come back today, successfully adjusted.



This unit had cal last time in 90's, presumably by Keithley during manufacturing.

Had learn few things:

* Around 2V offset on 1000VDC range is due parts drift, compensated by calibration. I had this offset on most of my 2001's.
* Firmware A05 had issue with AC measurements on low freq (10 and 20Hz), it was fixed by firmware A08. Unless A08 installed unit was not able to pass calibration.

As received report
As returned report

So prior to sending K2001's to callab - make sure you update ROM firmware chip to latest FW (A08 so far, not sure about "B" firmwares).

YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 

Online TiN

  • Super Contributor
  • ***
  • Posts: 3870
  • Country: tw
  • xDevs.com/live - 24/7 lab feed
    • xDevs.com
Re: Restoration glory of Keithley 2001 DMM
« Reply #74 on: February 08, 2014, 04:35:00 am »
Small update:

Checked K2001 current source in ohm's measurement mode, by using 2400 SMU in voltage source mode.



Also checked again self-test result on variable input mains:
AC Source - Chroma ATE 61505, local vsense

Now after calibration errors (200.2, 200.3 ? 401.1) only with low threshold voltage 90 VAC and 180 VAC with frequency 400Hz.
Before calibration and with firmware A05 it was failing all voltages with 50 and 400Hz, only 60Hz was passing.

Setup:



Summary results.
YouTube | Chat room | Live-cam | Have documentation to share? Upload here! No size limit, firmware dumps, photos.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf