Restoration glory of Keithley 2001 DMM

[VintageNut]

KI 2001 Last Calibration year 2000. Has the following errors

Testcal           201.3
A/D Mux  /Buff   300.2
Ohms Pretect   302.2
Input Protect   303.2
Ohms               304.2
Ohms           304.3
Ohms           304.4
Ohms           304.5
Ohms           304.6
Ohms           304.7
Input /100           305.2
Cal Divider           307.2
Cal Divider           307.3
4 Digit           308.1
Amps                   309.1
Amps                   309.2
Amps                   309.3
Amps                   309.5
Amps                   309.6
Amps Protect   310.1
S/H No. 2          406.6
Front End          407.1
Front End          407.2
Front End          407.3
Freq Cmp          409.6
TRMS          410.1
TRMS Filter       411.1
TRMS Filter   411.2
ACA Switch   412.1

Analog Daughter board 2001-162-04J



Digital Board 2001-142-06J



Analog Main Board 2001-102-04K

[ManateeMafia]

I see a capacitor soldered to R851. I don't remember seeing that 'mod' on another converter board. It looks like it connects to the DGND pin.

[VintageNut]

Your are correct. Good eyes! It is definitely a white wire special.

None of the functions work even close to what you would expect.

All of the voltage regulators near the transformer get very warm. The large PLCC on the daughter board gets very warm.

I suppose its time to get out the DMM and start checking voltage rails.

Is it safe/wise to operate the instrument with the daughter board off?

[TiN]

Yes, but your reference and bunch of other stuff would not work. Good enough for psu checks.

AD CPLD get little hot but not too much. It takes 5V rail.

Replace all electrolytics on both boards before you do anything.

[VintageNut]

Yes, but your reference and bunch of other stuff would not work. Good enough for psu checks.

AD CPLD get little hot but not too much. It takes 5V rail.

Replace all electrolytics on both boards before you do anything.

Ok. I will have to make a list and order the capacitors all at once.
It looks like 8 electrolytics on the analog main board and 4 electrolytics on the digital board.

The 2001 passes all key press tests and passes the display tests.

[VintageNut]

Closer inspection shows surface mount electrolytics on the converter daughter board and the analog main board.

Have you replaced those electrolytics as well?

[TiN]

If you mean tantalums, no, you can leave those alone.

[VintageNut]

If you mean tantalums, no, you can leave those alone.

Ok. Thanks.

Are the 4 regulators close to the power transformer running hot on your 2001s?

[TiN]

I posted thermal photos before :



You can see them all in my K2001 repository.

Usually if someone buy old 2001, I would do next:

1. Take boards of meter, take photos (try not to use flash, to avoid glare on PCB )
2. Upload photos for my collection
3. Replace all thruhole electrolytic caps. You will need 470uF x 63V 2pcs, 2200uF x 35V big ones, 1000uF 50V x 3pcs, 2200uF x 16V - 1pc, 1000uF 35V x 3pcs (for digital board), 47uF x 63V for digital board.
4. If there is electolyte gunk from old caps - you must desolder stuff around affected area, clean area very well, solder parts back. Believe me, this will save you DAYS of troubleshooting...
5. If any traces damaged/black - repair them. Pay attention to little vias around, to make sure they are not eaten/open.
6. Assembly stuff back, power on, check voltages (5V digital, 5V analog, +15V, -15V, +8VF, -8VF (there are test pads near A/D board connector), +38V, -38V (test pads near AD637)).
6b. Replace fan, usually they are bad in all old units (You need 40x40mm 12V 0.1A DC Fan).
7. CR11x avalance diodes near transformer must be cold, if they heating up - something around them and caps is messed up.
8. If all voltages within few % tolerance, run self-test and report what errors occur
9. Dump firmware and 24C16 calibration ROM contents, upload them for our collection

304.6,304.7 errors on ohms are usually contamination/dirt around ohm source ranges (Area around U325). If lower 304.x errors present - check Q320,Q311,Q312.
Correct voltage reference on pin 1 of A/D connector is -10.xx VDC.

[TiN]

So, did one of you get the non-working 2001 on ebay for ~$205 today?

I know who got it  (Not me  )

[VintageNut]

I posted thermal photos before :



You can see them all in my K2001 repository.

Usually if someone buy old 2001, I would do next:

1. Take boards of meter, take photos (try not to use flash, to avoid glare on PCB )
2. Upload photos for my collection
3. Replace all thruhole electrolytic caps. You will need 470uF x 63V 2pcs, 2200uF x 35V big ones, 1000uF 50V x 3pcs, 2200uF x 16V - 1pc, 1000uF 35V x 3pcs (for digital board), 47uF x 63V for digital board.
4. If there is electolyte gunk from old caps - you must desolder stuff around affected area, clean area very well, solder parts back. Believe me, this will save you DAYS of troubleshooting...
5. If any traces damaged/black - repair them. Pay attention to little vias around, to make sure they are not eaten/open.
6. Assembly stuff back, power on, check voltages (5V digital, 5V analog, +15V, -15V, +8VF, -8VF (there are test pads near A/D board connector), +38V, -38V (test pads near AD637)).
6b. Replace fan, usually they are bad in all old units (You need 40x40mm 12V 0.1A DC Fan).
7. CR11x avalance diodes near transformer must be cold, if they heating up - something around them and caps is messed up.
8. If all voltages within few % tolerance, run self-test and report what errors occur
9. Dump firmware and 24C16 calibration ROM contents, upload them for our collection

304.6,304.7 errors on ohms are usually contamination/dirt around ohm source ranges (Area around U325). If lower 304.x errors present - check Q320,Q311,Q312.
Correct voltage reference on pin 1 of A/D connector is -10.xx VDC.

Thanks. I will do all of that.

I wonder if the high heat of the regulators is a cause of the nearby electrolytic capacitors failure. I also wonder if installing some massive heatsink to the regulators , getting the heat out of the regulators, may improve the reliability of the capacitors.

[TiN]

Its usually combo of factors, like fan failure (on two 2001 i have fans were dead), high temps, and old age of caps. I would keep stock heatsinks, in case you may want sell meter in future, just use proper high quality 105 degree rated caps from respected vendor.

[VintageNut]

Its usually combo of factors, like fan failure (on two 2001 i have fans were dead), high temps, and old age of caps. I would keep stock heatsinks, in case you may want sell meter in future, just use proper high quality 105 degree rated caps from respected vendor.

For sure I would keep stock heatsinks.

Here is my reasoning. The internal temperature of a 2002 I am using is above 110 F. If the regulators are much hotter than the air temp, the capacitors close to the regulators may be much closer to 105 C than to 110F. If the regulators can be kept much cooler, that may help the reliability of the capacitors nearby.

[PaulAm]

VintageNut passed his 2001 on to me; now I'm looking at it.

I'll put together a cap order, but I'm looking at that 201.3 fail.  That has the same symptoms and V measurements that SKE reported way back at the beginning of this thread.  Unfortunately, he disappeared without reporting a resolution. 

I see 6.98V referenced to COM at pin 6 of U330, 7.4V at pins 2 and 3 and 7.22 at pin 7 of U318 (the output of U327, which should be 1.75V)  Obviously the last is wrong, the first looks reasonable but what about the other two measurements?

The power supply voltages all looked good.

edit: OK, this looks like a bad U330.  The leading edge of REFCLOCK is bleeding through and the output is a fuzzy squarewave on top of a DC level.  If I'm reading the schematic right, I should be seeing a 0-7V squarewave that's integrated by U327.

[Jay_Diddy_B]

Hi Group,

I can report a successful repair of a 2001.
I bought the meter for $30.00 CDN ($24 USD or 21.60 Euro.

It was missing the bridge rectifier on the Digital Board, the NAT488 chip.

It is also missing the outer cover, rear bezel and needs a replacement keypad because of one of the buttons is damaged.


After I installed the rectifier, the meter powered up and I was able to make measurements and get reasonably good results.

I ran the self-test and got a whole pile of errors. Having read this thread I decided I should start by replacing all the electrolytic capacitors. Here is the capacitors that I pulled out:



I did not find any damaged tracks, there was little electrolyte on the board. I scrubbed the board with alcohol (IPA) and then fitted replacement capacitors. Here is the list of capacitors I bought:



I have also attached a pdf with the capacitor list.

Here is a picture showing the new caps installed:



The unit now passes all the self-tests except two:



This one will probably go away if I install a NAT488:



The other error I believe is also related to the missing NAT488 chip:



I am looking for some case parts:

Cover
Handle
Rear Bezel
Rubber Keypad

Can anybody help?

Regards,

Jay_Diddy_B

[TiN]

Great, thanks for photos.
You sure they are UCC caps are original? All KZE's I had are brown plastic color, not black like on your photo. 

Where did optocouplers near input selection switch go? You need those back
I have spare digital board, which have some issues (often does not boot), but have all the parts on it.
I can send it for you and optocouplers, if you don't mind pay shipping (~30-40USD or so).

Btw, for a general note - GPIB chipset (NAT488 or compatible part) can be found on many similar instruments.
One of my boards was missing GPIB chip too, and I salvaged it from Keithley 7001 (bought for 50$).

[Jay_Diddy_B]

Great, thanks for photos.
You sure they are UCC caps are original? All KZE's I had are brown plastic color, not black like on your photo. 

Where did optocouplers near input selection switch go? You need those back
I have spare digital board, which have some issues (often does not boot), but have all the parts on it.
I can send it for you and optocouplers, if you don't mind pay shipping (~30-40USD or so).

Btw, for a general note - GPIB chipset (NAT488 or compatible part) can be found on many similar instruments.
One of my boards was missing GPIB chip too, and I salvaged it from Keithley 7001 (bought for 50$).

I hope the UCC caps are original, they are dark brown, I bought fresh ones from Digikey. I did not want to do the repair with New Old Stock (NOS). I have lots of NOS caps, but it is such a pain to change them. I went with fresh caps from a official distributor.

Thank you for the kind offer to send me a spare digital board. The opto-couplers are in the board, for some reason they are mounted on the solder side with a jumper on the component side to correct the wiring. I suspect that they may have been changed at some point. The meter seems to work properly.

Do you know the function of the opto-couplers?

I may have the NAT9914BPL on an old GPIB board for a PC. I haven't had a good look. I wanted to make that the analog section was working properly before I fixed the missing part. The part was used on NI GPIB PC-II/IIa ISA bus cards:



Regards,

Jay_Diddy_B

[TiN]

That chip is bigger PLCC on GPIB-PCII photo, will not fit.

Optocouplers are part of input protection and input buffer circuitry.

[macboy]

...

I may have the NAT9914BPL on an old GPIB board for a PC. I haven't had a good look. I wanted to make that the analog section was working properly before I fixed the missing part. The part was used on NI GPIB PC-II/IIa ISA bus cards:

Regards,

Jay_Diddy_B

9144 != 9914
I have a few 7001 switching systems, and I may be willing to part one out for a nominal cost. That will provide you with the cover, rear bezel, 9914 IC, and maybe the switch membrane. Sadly, they were rack mounted so I don't have handles. You can buy a "2000 Benchkit" from places like Mouser, etc., for around $25 or so. This includes the feet and handle. They used to sell the pieces of that kit separately for a total cost of around $12 but I think they have wised up since then.
Where in Canada are you? I'm in Ottawa.

p.s. Keithley has parts distributors in Canada as well, but generally they have a $250 or so minimum. I had wanted to replace the front panel of one of my 2001's, but that came to only about half of that.

[TiN]

Cover from 7001 is not compatible with 2001, if we talking outside chassis thing.

[macboy]

Cover from 7001 is not compatible with 2001, if we talking outside chassis thing.

Too bad. I hadn't checked. Is it a length difference?

[ManateeMafia]

The 7001 is missing the vent holes. I accidently put a 7001 cover on my 2001 and realized the vent holes were missing. I think with the right measurements, some holes could be made to fix that issue.

[PaulAm]

Mouser doesn't stock the benchkit, but Test Equipment Depot does.  They have it through Amazon, but it's cheaper to go direct.  Base price on that is now $31 + s/h, so figure $40+ for the handle and feet.

That takes care of the handle, anyone got a rear bezel they would sell?

[dadler]

The 7001 is missing the vent holes. I accidently put a 7001 cover on my 2001 and realized the vent holes were missing. I think with the right measurements, some holes could be made to fix that issue.

On this topic, anyone know if the 7001 cover is compatible with the 2015 series? I don't think either of them have "vent holes"?

The 2015-P I just bought on eBay is missing the feet and handle, so I was hoping to swap those over from a 7001 to my 2015.

My 2015 case is a bit gouged up as well, so if the cover swaps as well that would be great.

[macboy]

Mouser doesn't stock the benchkit, but Test Equipment Depot does.  They have it through Amazon, but it's cheaper to go direct.  Base price on that is now $31 + s/h, so figure $40+ for the handle and feet.

That takes care of the handle, anyone got a rear bezel they would sell?

If you are ordering parts, the Keithley part number for the rear bezel is 428-303.