Author Topic: Restoration glory of Keithley 2001 DMM  (Read 304011 times)

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Offline openloop

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Re: Restoration glory of Keithley 2001 DMM
« Reply #750 on: April 15, 2019, 10:23:44 pm »
Looking at the schematics, it appears that the main CPU gets its line readings straight from main power transformer taps. Digital board's U628 (page 2 of addendum part 2) is a comparator which detects zero crossings and feeds them straight into the CPU (pin 56)   
 
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Offline smps

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Re: Restoration glory of Keithley 2001 DMM
« Reply #751 on: February 03, 2021, 05:46:36 am »
Hi Tin, do you have CPLD bin file for the ADC board? thanks
 

Offline Uranium Fever

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Re: Restoration glory of Keithley 2001 DMM
« Reply #752 on: March 21, 2021, 09:00:04 pm »
Hi guys,

I found a dead Keithley 2001 in the dumpster two years ago and tried to revive it. After replacing all leaking caps and broken diodes, the high current resistor, and a destroyed trace, there is one (obviously) dead part left, which I could not yet replace. The VFD inverter ERG E705-E905VF also contained an exploded cap and other burned/etched components. Unfortunately I destroyed the transformer, when I dug out the components from the epoxy. Tektronix would only sell me a whole new digital board, and erg power does not have any spare parts left. I already tried to reverse engineer the part and rewind a transformer on a new core but unfortunately I did not get it to work. I'm a chemist and electronics is just one of my hobbies, so maybe I got something wrong, like the magnetic specifications of the core material, the winding or details in the connections.

Does someone here have a surplus inverter brick which I could buy?

Thank you to all for the priceless info you put on this forum
Stefan

 

Offline tonyz663

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Re: Restoration glory of Keithley 2001 DMM
« Reply #753 on: November 25, 2021, 04:23:56 pm »
I saw this topic for the 2001 DMM and it is a wealth of knowledge!  I have a 2001 (firmware is B10) that I just purchased with an ADC error 200.1 that is constant.  When checking voltages, I find that the +8V and -8V supplies seem off.  The +8v is reading around 5.5-6V and the -8V is a bit better at -8.5-9V.  All the rest of the voltages are good.  I am re-capping it now as well.  The +/- BS supply seems good too (+/- 37.3V).  The CR200 diode is in that +/- 8V supply circuit and is hard to find.  The TIP 101 and 106 are available (TIP 102 and 107 at Mouser).  While I am re-capping, I wanted to replace the +/- 8V supply components too, since that analog board takes a bunch of time to remove!  Would that power supply voltage cause the error I am seeing or is there another area I should look into to solve it?  Let me know your thoughts!
 

Offline TiNTopic starter

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Re: Restoration glory of Keithley 2001 DMM
« Reply #754 on: November 25, 2021, 04:41:58 pm »
Quote
Does someone here have a surplus inverter brick which I could buy?
Inverter brick can be stolen from Kei 7001, it's sometimes available cheap. Also VFD in case you need one :)

Quote
since that analog board takes a bunch of time to remove!
After 5th try you'll be proficient at it , trust me  ^-^

Quote
CPLD bin file for the ADC board?
Nope, didn't feel investing into old tools to read old CPLDs.
« Last Edit: November 26, 2021, 12:20:38 am by TiN »
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Offline RikV

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Re: Restoration glory of Keithley 2001 DMM
« Reply #755 on: December 29, 2021, 04:18:44 pm »
Anyone any experience with ARRAY M3500A. It is said to be internally the same as a K2000?
 

Offline doktor pyta

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Re: Restoration glory of Keithley 2001 DMM
« Reply #756 on: December 29, 2021, 07:45:38 pm »
Search for Picotest M3500A
some pictures https://www.ruten.com.tw/item/show?21934534475535
I think it is similar but not identical.

Online Andreas

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Re: Restoration glory of Keithley 2001 DMM
« Reply #757 on: December 29, 2021, 07:56:13 pm »
Anyone any experience with ARRAY M3500A. It is said to be internally the same as a K2000?
AFAIK: It corresponds to the Keithley 2100.

With best regards

Andreas
 

Offline RikV

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Re: Restoration glory of Keithley 2001 DMM
« Reply #758 on: December 29, 2021, 09:54:26 pm »
Thanks, but that doesn't make things simpler. I am in the process of looking for a second hand 6,5DMM that fits my budget and is preferably in working condition.
This is what I found so far (price ranges are in €, ex H&S)):
34410A 318-903€
34401A 354-427€
34460A 899€
34461A 938€
K2000 500-700€(of course depending on age?)
k2100 773
Array M3500 Has already been reserved
K2700 771 (can be used as DMM I understand?)

I am struggling through the specs of these beauties to decide, but could you guys tell me what your preference would be and why? I don't care about the colour of the case if you know what I mean.
 

Offline TiNTopic starter

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Re: Restoration glory of Keithley 2001 DMM
« Reply #759 on: December 30, 2021, 01:16:08 am »
34410A is the best option, if you don't mind little older simpler UI. Stay away from K2100/Array. K2700 is nice if you need multichannel often. There is also HPAK alternative for that which is 34970A (essentially 34401A strapped to scanner card option).
« Last Edit: December 30, 2021, 01:18:20 am by TiN »
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Offline Zucca

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Re: Restoration glory of Keithley 2001 DMM
« Reply #760 on: December 30, 2021, 03:50:44 am »
34410A
Can't know what you don't love. St. Augustine
Can't love what you don't know. Zucca
 

Offline RikV

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Re: Restoration glory of Keithley 2001 DMM
« Reply #761 on: December 30, 2021, 10:57:53 am »
Is it possible to use a K2700 without any scanner card plugged in? How does it compare in terms of usage to a, say, 2000 or 34410? In other words, can I forget it has a scanning function?
Found the answers I think. Yes. But apart from the 2700 having no rear connections, is there any difference in functionality? Is 50 readings/sec adequate for "normal" usage?
« Last Edit: December 30, 2021, 11:29:54 am by RikV »
 

Offline doktor pyta

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Re: Restoration glory of Keithley 2001 DMM
« Reply #762 on: December 30, 2021, 04:37:58 pm »

Offline syau

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Re: Restoration glory of Keithley 2001 DMM
« Reply #763 on: March 31, 2022, 02:46:40 pm »
Recently scored a Keithley 2001, self test give 308.1 when cool (within 5-10 minutes after power up), replaced U319 and the result is the same, R212 measured ok.

Replaced all cap as per this forum, all caps are clean no leakage, upgraded to B17 firmware. Selftest still give error 308.1.

Hooked to my 732B, the reading are very stable for 1 week until today which read ~400mV low and fluctuating up and down. Change range to 200V and the reading become steady. Try to troubleshoot the input ranging divider but got lost  :-BROKE

Gratefully if some members can provide some hints.
 

 
 

Online Kleinstein

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Re: Restoration glory of Keithley 2001 DMM
« Reply #764 on: March 31, 2022, 03:23:25 pm »
For the self test error one could run the self test one at a time and than in the failing test part check if the test signal is OK at a few test points with a 2nd meter. So in this case look how far the 0.78 V go.

For the 10 V range fluctuating there are several parts that could go wrong. A first is checking the supplies and ADC references. There are several refrences - a Zner diode based one on the ADC board and the LM399 as the reference for the accuracy.

With 10 V or 0 V at the input the ADCs in signal would be an interesting test point too. This may show if the problem is more with input buffer / divider or with the ADC and references.  The input stage as settings for x -0.5  , x 1 , x 5 and x 50. So it is a bit confusing and the x -0.5 mode for the 20 V range uses a quite different signal path compared to the other modes.
 
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Offline syau

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Re: Restoration glory of Keithley 2001 DMM
« Reply #765 on: April 01, 2022, 12:41:25 pm »
Compared 2V/200V vs 20V regarding the DC_STB register found most different is on U300 which Q7, Q6, Q4 are connected to U319, will replace U319 again once I got the spare.
 

Online Kleinstein

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Re: Restoration glory of Keithley 2001 DMM
« Reply #766 on: April 01, 2022, 01:02:41 pm »
There are quite a few parts involved in the gain switching. If U319 was already replaced, I doubt it would be bad again - maybe fake when from a unreliable source.
It would likely be better to first localize the error a little more, before exchanging parts.  With the ADC card in the way, one may have to solder wires to a few relevant testpoints.

The Lm339 used to drive JFETs are know to sometimes fail - not just in this meter but others too. So I would somewhat suspect them.
 

Offline maxwell3e10

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Re: Restoration glory of Keithley 2001 DMM
« Reply #767 on: April 02, 2022, 09:17:52 pm »
This thread has been going on for almost 10 years! And I myself first found EEVblog when I was trying to fix a K2001 in 2016. So seeing this thread pop-up made me want to try one more time to fix this same meter.

It shows overflow on all ranges and the first error that comes up is 200.1. In the past I checked that swapping the ADC module from another meter fixes the problem. This time I more carefully looked at the signals. It seems like the integrator and comparator work fine and respond to input changes, but the DATA_OUT from ADC is always zero.

It makes me suspect the problem is with U808, EPM5128LC. Is there anything else I should check first?

Assuming the Altera chip is bad, it is stamped with 2001-802A05. Maybe someone be willing to sell it from a donor meter?

« Last Edit: April 03, 2022, 03:03:48 pm by maxwell3e10 »
 

Online Kleinstein

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Re: Restoration glory of Keithley 2001 DMM
« Reply #768 on: April 02, 2022, 09:56:24 pm »
If the integrator waveform still looks reasonable, the main part of the U808 is still working. It is only the data out part that may not work.
This goes to one of the opto-isolators and AFAIK also a connector that can have contract problems. So it would be about following that signal and maybe check for a short.
 

Offline maxwell3e10

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Re: Restoration glory of Keithley 2001 DMM
« Reply #769 on: April 09, 2022, 03:28:13 am »
By swapping the Altera EPM5128 chip from another Keithley 2001 meter I can definitely verify that is the problem.  I'll try my luck next week with Keithley tech support, see if they would be willing to sell a replacement chip.
 

Offline Smith

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Re: Restoration glory of Keithley 2001 DMM
« Reply #770 on: April 09, 2022, 05:52:04 pm »
Is it possible to use a K2700 without any scanner card plugged in? How does it compare in terms of usage to a, say, 2000 or 34410? In other words, can I forget it has a scanning function?
Found the answers I think. Yes. But apart from the 2700 having no rear connections, is there any difference in functionality? Is 50 readings/sec adequate for "normal" usage?

Yes, It will just work like a normal Keithley 2000. It's basically the same, the specs are about the same if I remember correctly. There's a multiplexer card for the Keithley 2000 too, but as far as I know it was for the 2000 only. It's just a multiplexer with an wired output which connects to the rear input. The Keithley 2700 cards are just screw in cards with internal connections. I guess they are the same as the 2701, basically the Ethernet enabled version of the 2700.
Trying is the first step towards failure
 

Offline TiNTopic starter

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Re: Restoration glory of Keithley 2001 DMM
« Reply #771 on: April 09, 2022, 09:25:23 pm »
maxwell3e10
I have 2001 ADC board somewhere.
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Offline maxwell3e10

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Re: Restoration glory of Keithley 2001 DMM
« Reply #772 on: April 10, 2022, 02:13:44 am »
Thanks, TiN! I thought if anyone here, you might have one in parts drawer. Let me see if I hear anything from Keithley/Tek, if not, I will PM you.
 

Offline mzzj

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Re: Restoration glory of Keithley 2001 DMM
« Reply #773 on: April 10, 2022, 12:49:52 pm »
Yet another 2001 here: partly burnt pcb under one of the capacitors and shorted secondary windings on transformer. I'm assuming shorted pcb cooked the transfomer.

PCB is fixed to somewhat working condition to verify that there is no major underlying problems. (needed 2x12v transformer and  2 lab power supplies..)
Only one error on self-test  so I'm planning to rewind the shorted transformer secondaries.

Washing the pcb? I was planning to go with my usual: warm soapy water, after that RO-water, compressed air, IPA and compressed air again.
What do you do with the Rear-Front switch? Remove it or keep the area out of liquid?
 

Offline syau

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Re: Restoration glory of Keithley 2001 DMM
« Reply #774 on: April 11, 2022, 05:50:08 am »
Compared 2V/200V vs 20V regarding the DC_STB register found most different is on U300 which Q7, Q6, Q4 are connected to U319, will replace U319 again once I got the spare.

Looks like I fixed my unit by removing the U319, cleaned the area and re-solder it.

Note: The DG211 come from an Agilent part board.
 


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