Restoration glory of Keithley 2001 DMM

[Zucca]

Any idea if we can do the same here with the MEM2 chip Dallas DS1245Y? Sorry if it was a stupid question, I am not an expert here.

I did some homework and indeed it was not a clever question...

First of all we need to find a 32 pin parallel FRAM, like this one FM28V100:
http://www.cypress.com/?docID=50822

Second it is not 1:1 pin compatible, so we need to build an adapter board.

Third that FRAM runs with 3.3V and not 5V like the DS1245Y, so a VREG should go on that adapter and pray the 3.3V FRAM will be interpreted from the 2001 as logic "1".
Fourth the FM28V100 has two chip enables pins CE1 and CE2... (not a show stopper but another difference)

It´s not looking to be that easy. Still it is a cool Week End project to work on.

[TiN]

ManateeMafia

Thanks. Can you drop your B13 as well?

I finally decided to make overall page with all files/data/firmwares for all Keithley gear in one place.
Will see how that goes.
You will likely to loose calibration, but I don't remember 100%. Just save 24C16 I2C ROM contents, all calibration of 2001 reside in there, as well as serial number.

I was wondering how much would be cost of front panel plastic for 2400 (part number 2400-313A), since mine 2400 have it quite busted up. Can you ask them about it as well? No need PCBA , just plastic with VFD panel plastic. It's  more topic for my 2400, which is somehow gone. 

[ManateeMafia]

I made a mistake about fw rev. It should have been B15. I also have B08 but I believe you already have that.

The front panel is not cheap but it includes the front cover, lens, and banana jacks. I am pretty sure the overlay is also included. The price is around $150 US.
Are you missing the entire panel or just the lens?

I plan on replacing the missing cover for the scanner board and adding the missing feet.

The front panel is not in the parts list. It is part RPT-FP2001.

I don't have a price for the VFD but it is part RPT-2001-110 according to tech support.

[ManateeMafia]

I forgot to mention that I asked about the resistor R-289-1G and they told me the specs are.. 1.5W, 10kV, 2% accuracy, and a tempco of 200ppm. There are several suitable resistors that should meet those requirements. The 10000ppm characterization should be achievable with a 3458A or equivalent.

[Zucca]

I always wanted a nanovoltmeter.....

Just found the 1801 Nanovolt preamp option Manual with Schematic of the board which goes inside the 2001.
https://public.magnet.fsu.edu/Graf/Manuals/Keithley/1801%20Nanovolt%20Preamp.pdf

Here the datasheet:
www.keithley.com/data?asset=356

We need now to understand what is in the box outside the Keithley 2001, oh dear another reverse engineering project in my list... anyone has this rare animal available?

[ManateeMafia]

I was going to post the same info the other day but forgot. When the secret menu option showed the 1801 I was hopeful that a plug-in board could be constructed using the schematics.
I have been keeping an eye open for that option for the last year but I have not seen it cheap. I believe it was listed once for around $2K US.

It is nice that it supports AC unlike the 2182/A and 34420A. I have picked up an Agilent 34420A (or two) in the last year but I have wondered if the AC function would be worth adding to my 2001. The additional milliohm ranges are nice too.

The plug-in board has an eeprom but it probably just has a serial number. The new secret front panel menu will probably set the serial number when the option is enabled.
A good place to start might be the 34420A schematics. They are available but pretty poor quality. I will make an effort to scan some if they are wanted.

[Zucca]

ManateeMafia

I already contacted 2 companies (one in Germany and one in USA) to get a quote of this puppy. If it is below or equal €500 I will take it home (it will never happen, my guess is €1000 easy).
Maybe I can push them down because I know this used stuff is not going to sell quick, so I imagine those boards sitting on a shelf for years (waiting for me).

Anyway yes, this 2001 is becoming a (even more) wonderful project.

PS: Once I got the 10ch option boards I will upload nice pictures of it.

[TiN]

Very great find.
I bet it something like described in this patent : US6069484

I have 2001-TCSCAN card, might post pics of it later.

And we might end up having own preamp, ha

[ManateeMafia]

I was thinking that it might be useful for a flicker noise amp or possibly a low noise preamp tied with some low thermal relays controlled by the digital io on the back of the meter.

Something similar to lymex's project https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/

I don't know how much space is available. A breakout board would be handy.
Does anyone know if a breakout board was made by Keithley?

[mmarks3141]

No breakout board was made that I can remember.

[TiN]

Time to get back to drawing board...

Updated schematics of analog board parts, around U5xx parts.

As of switching board, there is existing 2001TC-SCAN, with spec Contact Potential: <±500nV typical per contact, 1uV max (except CH5 and CH10, which are 2uV).
I do have it, in case anyone interested. It also have AD590 thermal sensor coupled to copper bar on bottom side of PCB in terminals area to measure CJC.

Instruction manual for it does have full schematics as well.

[TiN]

Today is a good day.

Got unit #2 fixed, passes selftest now w/o issues.
It require full recalibration tho, since I got this unit with missing LM399, LTC1043, and other critical parts, so replaced these parts with new ones from Digikey.
With 1.00000V from my EDC it measures 0.986V 



Will post article with photos later.

P.S. Tomorrow I also post something which all of 2001 owners would be superhappy to see 

[ManateeMafia]

Great job. 

I also got my second one passing all tests (again). I had to repair some damaged traces under/around U505. Pin 8(Vss) was floating and was throwing 409.6 errors. It seems to be working now.

I have been looking at the preamp option like the Keithley 1801, but I cannot decide where to start. The plug in board seems straightforward but the preamp will be an interesting project by itself.
I know it is not trivial to build something that sensitive, but it would more of a learning experience. The most interesting article I have read so far is from Jim Williams . I was looking for a link to add here but I noticed you already have it on xDevs http://dev.xdevs.com/projects/rnd/repository/revisions/3a68a7e9a562/raw/Linear/Documentation/LTMag-V16N01-11-FETAmp-Williams.pdf

I guess this may be related to the preamp design you recently mentioned?

[TiN]

As for preamp I plan to have it as separate device. This will allow using it not just with K2001, but also with other gear, like scope and such.

[macboy]

Today is a good day.
...
P.S. Tomorrow I also post something which all of 2001 owners would be superhappy to see 

I know what it is   
And it will be a game changer for those of us working to fix up these gems.

[ManateeMafia]

 LTZ1000(A)? MickleT or TiN rewrote the firmware to make it like a 2002? 

[TiN]

Much better, full schematics from Keithley. 



macboy did found military version Keithley 2001M up for sale yesterday with photos showing schematics addentum for repair manual, and guess what, entering that into google gave this. Obviously US government did not like having 2001 without schematics, so those documents were disclosed for mil customers. 



2001M also had B17 firmware version, which likely support 400Hz line frequency. Little birdie told me there is no RMS measurement different to usual 2001's.

Downloaded and rehosted documents on my machine, since we don't know if original URL survive for long. Google cache says there were some documents for 26xx SMU, but now they are gone.

Model 2001 Multimeter, Calibration Manual, 2001-M-905-01 Rev. H / Mar 2011
Model 2001 Multimeter, Repair Manual Addendum Schematics part 2, 2001-902-07 Rev. C / March 2011
Model 2001 Multimeter, Operator's Manual, 2001-M-900-01 Rev. K / March 2011
Model 2001 Multimeter, Repair Manual Addendum Schematics part 1, 2001-902-06 Rev. C / March 2011
Model 2001 Multimeter, Repair Manual Addendum, 2001-902-05 Rev. C / March 2011

[ManateeMafia]

I must be going blind. I looked at that auction several times but did not notice the schematics were included.

[macboy]

2001M also had B17 firmware version, which likely support 400Hz line frequency. Little birdie told me there is no RMS measurement different to usual 2001's.

Good point about  400 Hz line frequency as would be found on submarines, aircraft, etc.
2001M specifically supports RMS-calibrated average-responding AC measurements in addition to the 2001's true-RMS and average modes. The difference is a correction factor applied to the average mode so that when used with sine waves, it gives the equivalent RMS reading. This is needed since so many military technical procedures are written for this type of meter response. The reading mode is selectable in the config menu for ACV and ACI.

Firmwares B16 and B17 (and maybe newer?) are for 2001M. Model 2001 then apparently goes up to B15. I am guessing that there is no hardware difference for 2001M and that the only actual difference is for the addition of the new AC mode, and maybe for adjusting integration time to 50 Hz mode in order to support a 400 Hz line.

It is worthy to note that the digital board schematic is for the version B firmware type (two DIP ROMs) not the older A type (one PLCC ROM).

I must be going blind. I looked at that auction several times but did not notice the schematics were included.

I have an eye for details like that. I was prepared to drop big coin on that meter just for the documentation, but then two things happened nearly simultaneously: TiN, armed with new keywords from those photos, found the docs with his google-fu, and the auction was pulled.

[TiN]

This one. It was ~470USD with 14 bids and day before end yesterday, and was pulled promptly after I asked seller if there are full schematics in those documents on photo. I don't know if it's coincidence, but I googled proper keyword like on those paper covers, and gotcha what we all were looking for.   

I think that will still work on my schematic version, since their reproduction is far from clear and few parts are rather cryptic. Not easy to read, specially having far from ideal analog circuit topology understanding. Also it does not reflect newer changes from more recent units (which I still hoping to get more photos , since I have only Rev L and Rev J analog boards, but I do know there are Rev H and Rev P in existence).

But at least no need to probe every friggin pin on every part for dozen times to trace signal routing in 4-layers. 

[ManateeMafia]

That explains why I couldn't find the auction this morning.

I cannot imagine the time you spent tracing out each component. It sucked tracing out a couple of IC's across the board.

[TiN]

B16 is still version for normal unit. I saw it on bay before (proof pic attached).
One more notice , S/N of that B16 unit is 1073931, 2001M from yesterday also starts with 1, 1411110.

Added calibration and operation manuals since they are different revision/more new than normal published ones from Keithley site. Don't know if any difference between, at first glance it's same.

macboy, where did you got information about RMS-function on -M?

Also I tested my primary 2001 with 400Hz (have Chroma 2000VA AC source at work lab), it was working even with usual firmware

[macboy]

... was pulled promptly after I asked seller if there are full schematics in those documents on photo. I don't know if it's coincidence,...

Probably not coincidence. He maybe thought he could get more money by selling the docs separately or something. I had also inquired about them. But now they are out in the wild and are no longer as valuable as any of us, or he, thought.

I think that will still work on my schematic version, since their reproduction is far from clear and few parts are rather cryptic. Not easy to read, specially having far from ideal analog circuit topology understanding. Also it does not reflect newer changes from more recent units (which I still hoping to get more photos , since I have only Rev L and Rev J analog boards, but I do know there are Rev H and Rev P in existence).

But at least no need to probe every friggin pin on every part for dozen times to trace signal routing in 4-layers. 

It must be maddening work. I'll check the analog board versions of my four units later. Mine span A06 to B15 firmware versions IIRC so I probably have a wide range of analog boards too.

...
macboy, where did you got information about RMS-function on -M?

Also I tested my primary 2001 with 400Hz (have Chroma 2000VA AC source at work lab), it was working even with usual firmware

http://lmgtfy.com/?q=2001m+site%3Akeithley.com
specifically:
http://www.keithley.com/support/data?asset=13096
http://www.keithley.com/data?asset=14876

[TiN]

I know about those documents, but I thought it's common for that firmware versions, not just 2001M. Just checked, my A08 and B15 units don't have that RMS-AVG.

Also since Keithley website require login/registration to download files, I got them all locally by DIY python robot. Every single "asset=N", with N from 0 to 100000.  5.5GB of files.

[macboy]

The version B16 firmware update document that mentions the RMS-AVG mode also specifically refers to 2001-M, not just 2001. You might not have noticed that in the past.