Keithley 2001 Calibration Failure Error #363 200uA Gain out of Spec

[mr.nicholaus]

Greetings,

I am searching here in an attempt to remedy a failure I get when performing the comprehensive low level calibration.

I have already replaced the Electrolytic Capacitors and the self test passes with no errors. I complete all of the steps of the calibrations once I enter the calibration due date. I get error +440 " Calibration not complete. Once I query the errors with SYST:ERR?

I get 200uA gain OOT +363. I have about 10 of these unit is house. I have only gotten 2 to pass the low level calibration successfully.

The one the passes has B17/A02. The two the fail so far have B16/A02. I think the issue is in the firmware.

I had planned to purchase blank AT27C040-90PU-ND, copy the firmware from my working unit and install in the other unit. BUT I think this will not w

We have a DATA man M-pro that will allow for copying the firmware, will I still need to perform the calibration after updating the firmware?

Any and all help would be appreciated

[ddcc]

Funny, I had the same problem with a 2001M: https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg2189003/#msg2189003

Don't think the problem is in firmware, I upgraded from B16 to B17 and it made no difference. But I wasn't performing low-level calibration, only the regular comprehensive calibration. What worked for me was replacing some of the analog switches, and then making sure to recalibrate in 4W mode.

[CM]

I have a Keithley 2001 firmware B06 that threw a 363 error on the open circuit section of the comprehensive calibration.  Replacing the analog switches U317, U320 and U323 resolved that issue.  Thank you ddcc for that great slouthing to figure out that one!  Replacing the LM399 precision voltage reference also breathed new life into this unit!  I am going to proceed with replacing the other 6 analog switches to see if I can drive down the ppm errors I am seeing on the resistance measurements.