Author Topic: Restoration glory of Keithley 2001 DMM (Read 306974 times)

TiN · « **Reply #500 on:** February 28, 2016, 04:42:27 pm »

Privet

This is the owner of infamous 2001M thanks to whom I got hint and found original Keithley's schematics for 2001.

Update your firmware ROM to A08. When I had my meter sent to Tektronix Cal 2 years ago, they were not able to calibrate it with older fw. After update to A08, everything went well.

Check frequency line, perhaps CPU cannot read mains frequency correctly, causing issues.

TiN · « **Reply #501 on:** March 04, 2016, 11:16:37 pm »

After whole night of debugging on latest Model 2001, and replacement all parts except rare U441 dual JFET, I finally unit fixed by replacing pesky Q512 with NXP PMBFJ620 in tiny SOT363 package.
Quick calibration show no errors and meter show nice readings.

It's not pretty, let me tell you, but works as proof of concept...

Already ordered U441 from UTSource on ebay store for final fix.

DMM passes Self-test without any problems (before was almost every 4xx error).

Time to go sleep, 7:23 AM here...

Macbeth · « **Reply #502 on:** March 05, 2016, 05:29:22 am »

TiN, what I would do is decap pesky Q512 and replace the die with PMBFJ620

Lots of old antique electronics restorers use similar tricks with ancient capacitors, batteries, etc.

plesa · « **Reply #503 on:** March 05, 2016, 07:47:18 am »

U441 is still manufactured by Micross www.micross.com, price £6.96.
https://www.micross.com/pdf/LSM_U441_TO-71.pdf

TiN · « **Reply #504 on:** March 05, 2016, 12:01:27 pm »

Manufacturer is Linear Systems, and Vishay Siliconix, but I think it would be longer and more expensive to buy one piece from them with shipping to TW, so I'd try luck with UTSource guys

Bought some parts from them before, was okay.

plesa · « **Reply #505 on:** March 21, 2016, 03:07:19 pm »

2001 arrived and it is in good conditions. ( small damage on front cover and metal enclosure). New cover quoted from Keithley $168, display lens $38.
After power up Error 514 ( DC calibration data lost) this will requite full DC calibration at least. For initial testing I will upload the dump from other instrument).
I have no idea how the data can be lost, unit seems to be intact calibrated in 2009 ( manufactured in 2005/2006).
followed by
304.3 Ohms Source - 89uA and 0.98mA Sources
304.4 Ohms Source - 7uA and 89uA Ohms Source
309.1 Amps - 200uA Range
These errors seems to be familiar and I expect some of DG411/DG404/DG211 switch, Q320/Q324 JFET or 4052 shift registers is not working properly.
Lowest current range is working properly, so faulty is Ohm current source.
And the fain is loosen which resulted in lot of vibration and noise.

Firmware is B16, uploaded to TiN site and already upgraded to B17 (K2001M) - used ST27C4001 UV EPROM chips instead original Atmel OTP 27C040.
Analog board is revision P, digital board revision K.
Memory upgrade to MEM2 -parts ordered:)

plesa · « **Reply #506 on:** March 23, 2016, 10:42:01 pm »

DC calibration data lost error during startup has been solved. The problem is corrupted memory U634 (24C164) after uploading data from one of TiN 2001 unit there is no error message during startup.
I'm not sure how data corruption can occur, probably swithing off unit off during saving calibration data. Plan is to decode and fix error with original data.

Ohm current source errors - current measurement is working properly and 20k, 200M and 1G Ohm ranges are not working. Unfortunately both suspected IC are thru hole.
I have no idea why they used THT instead of SMD like is used in 2002. Parts ordered.

Macbeth · « **Reply #507 on:** March 23, 2016, 11:34:44 pm »

plesa, did you upgrade the firmware? OK, not at all the same meter, but the K2000 has a famous DC calibration lost when upgrading from any firmware to latest A20. Even when getting this alarming DC cal data lost message (and proving it by measuring stuff) rolling back to an earlier firmware seems to restore good working order. Of course I made sure I saved my little 24C' EEPROM anyway, but there doesn't seem to be any need if you just roll back firmware.

Using someone elses backed up calibration is clearly not going to do you good.

plesa · « **Reply #508 on:** March 25, 2016, 11:41:35 am »

Quote from: Macbeth on March 23, 2016, 11:34:44 pm

plesa, did you upgrade the firmware? OK, not at all the same meter, but the K2000 has a famous DC calibration lost when upgrading from any firmware to latest A20. Even when getting this alarming DC cal data lost message (and proving it by measuring stuff) rolling back to an earlier firmware seems to restore good working order. Of course I made sure I saved my little 24C' EEPROM anyway, but there doesn't seem to be any need if you just roll back firmware.

Using someone elses backed up calibration is clearly not going to do you good.

Yes, I upgraded from B16 to B17 and error during startup was the same. I checked the backup of U634 and it looks like OK. So I tried to upload it back instead of TiN backup and error is gone.

plesa · « **Reply #509 on:** March 26, 2016, 04:21:33 pm »

Failed test 304.3 and 304.4 has been solved. It was component which I was not suspecting.
R365 78.7k 0.5% Vishay VSA100 foil resistor is open. I replaced it by two Vishay UXB series resistors in series and errors are gone

The best replacement I found is VSA101 series http://www.vishaypg.com/docs/63143/vsa101.pdf

plesa · « **Reply #510 on:** April 23, 2016, 10:30:57 am »

I was curios what is inside VSA100 resistor and also I wanted to identify failure mechanism of foil resistor.
So I remove epoxy potting from all foud sides and expose the resistor chip. Chip was coated by orange slicone.
The biggest surprise was that when measure the resistor is working and has 78k7. So it is contact or broken chip....

SeanB · « **Reply #511 on:** April 23, 2016, 11:56:36 am »

You will probably find it was a lead broken off at the glass substrate. Either took the pad with it, or cracked the glass off in that area.

klaus11 · « **Reply #512 on:** May 03, 2016, 12:34:06 pm »

K2001 has in secret menu 3458A simulator? As K2002

TiN · « **Reply #513 on:** May 03, 2016, 12:53:38 pm »

No, no 3458A mode nor 3458A game in 2001.

TiN · « **Reply #514 on:** May 08, 2016, 11:51:52 am »

Gave some hydrogen peroxide + sunlight love to one of my 2001's..
Photo before:

Photo after:

klaus11 · « **Reply #515 on:** May 08, 2016, 11:03:25 pm »

Nice!

Macbeth · « **Reply #516 on:** May 09, 2016, 12:01:10 am »

Hmm... nice, but I think I will go to the effort of removing the plastics that are not affected by the yellow peril, like the display panel and input jacks because they seem to have come off a bit worse

Also allows for safer 150C hot air treatment to reform the ABS to factory on all those edge dings. Something I learned of recently

What would be a good way of removing the scratches from the display panel? I've heard polishing with toothpaste and the like but in my experience it's been ineffectual or made matters worse on other stuff (notably scratched eyeglasses).

TheSteve · « **Reply #517 on:** May 09, 2016, 01:31:07 am »

For polishing display windows I recommend the Novus line of scratch removing products. I have used them with great success. The cloth you use to apply the product and buff the display window must be very soft or you'll never get anywhere. Obviously protect silk screen labels, stickers, or paint with masking tape before hand. Ideally you should also remove the display window from the chassis beforehand.
The last display window I did was on a Agilent frequency counter, you may not get it 100% but you can get in the high 90's.

AF6LJ · « **Reply #518 on:** May 09, 2016, 02:25:32 am »

You beat me to it TheSteve.
A friend turned me on to that stuff, works like a Bomb.

plesa · « **Reply #519 on:** May 09, 2016, 03:16:01 pm »

Quote from: TiN on May 08, 2016, 11:51:52 am

Gave some hydrogen peroxide + sunlight love to one of my 2001's..
Photo before:

Photo after:

It looks that it also remove Keithley marking on top left corner. But it seems to be only one alternative ( new plastic price is ridicilous).

TiN · « **Reply #520 on:** May 09, 2016, 04:26:37 pm »

That was mechanical damage from my careless tossing panel around in the jar.

macboy · « **Reply #521 on:** May 10, 2016, 01:01:21 pm »

Quote from: Macbeth on May 09, 2016, 12:01:10 am

...Also allows for safer 150C hot air treatment to reform the ABS to factory on all those edge dings. Something I learned of recently
...

How about credit where credit is due? I mentioned this technique in TiN's K2000 thread here. I came up with this crazy idea one day, decided to try it on a Keithley 199, and it worked like a charm. I am certain that I am not the first to do this but I hadn't heard of anyone doing it.

Here is an example. I fixed up a Keithley 7001 panel yesterday, including de-yellowing and fixing minor dings. These are very minor dings but I wanted to post up some pictures. I have fixed far worse.

1. Panel with lens removed, yellowing of the ABS plastic is quite evident.

2. Panel after ~2 hours in the sun with "40 volume" strength gel Hydrogen Peroxide hair bleach, brushed on straight from the bottle.

3. Small ding in a corner.

4. Ding removed with hot air, set to 170^oC and high fan.

5. Two small dings in side

6. Removed.

7. Side-by-side comparison with a unit awaiting restoration.

AF6LJ · « **Reply #522 on:** May 10, 2016, 02:51:16 pm »

That looks really good and almost like new.

TiN · « **Reply #523 on:** May 10, 2016, 03:00:20 pm »

Better than new - proven by time!

Thanks for great details and photos. I'll try and report back the progress once done. I have three 2001s, both 2002 and 2304 panels in line.

plesa · « **Reply #524 on:** May 18, 2016, 06:42:01 am »

To prove hydrogen peroxide whitening I submerged covers from K2002,K2001,K6517 and K2410 in 15% hydrogen peroxide. After 2h there was small change, but after one day they are like new. Thanks for hint


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Author Topic: Restoration glory of Keithley 2001 DMM (Read 306974 times)

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