Keithley 2000 self test fualts. - Page 1
Forum section: electronics / testgear

author: bentwrench
author_rank: Newbie
timestamp: April 21, 2023, 09:42:57 pm
content: Hello all.I have a Keithley 2000 I recently acquired. The unit appears to be functional. I have not checked for accuracy on any of the readings yet, other that to see things are in the "ball park". I ran the self test and I get faults in 301.2, 302.2 The are faults on the HI Ohm, 2 Wire Sense.I switched the to the rear inputs and repeated the tests and got whole pile of faults, switched back to the front panel and then it reported 301.2, 302.2, and also 303.2 (which is Hi Ohms). So before I started digging around I was wondering if the input switch needs to be cleaned. I have the repair manual, and a good schematic but I have never worked on one of these before. I suspected the switch because it feels a bit spongey, but I don't know how it is supposed to feel.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 22, 2023, 05:29:30 am
content: The feeling of the switch usually does not change with dirty contacts. It may feel a bit spongey due to the puch rod used, so this may be perfectly normal.In the simplest case the switch may just need a few (e.g. 10) operation cycles as the simplest for of cleaning.However the switch should normally not effect the self test. It is possible that some of the error reports are boarderline and may or may not happen all the time, likely not related to the switch. The switch can cause trouble, but AFAIK the self test has no way to check that part. So I am afraid the problem is more than just a dirty switch. It looks like a problem with the current source for the ohm mode.There is a small chance that the defect is also in the protection part, that is also used in V mode. So until checked I would not use the meter with higher voltages (e.g. > 15 V) that may cause more damageIt may be worth using a separate meter an measure the test currents in the 2 wire ohm mode and the different ranges.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 22, 2023, 07:25:14 am
content: The switch can be the source of several fault codes for ohms and current, I got my K2000 cheap because it had 600.1 and 600.2 faults, which I cleared by dosing the f/r switch liberally.It's always worth eliminating this as a cause first, before moving to more complex repairs.

author: bentwrench
author_rank: Newbie
timestamp: April 25, 2023, 03:09:06 pm
content: Had time for a little further investigation. I took cover off and didn't see any obvious visible damage. The meter works as it should, while I can't verify calibration as the only other bench meter I have is an old Fluke Hydra. It agrees well with the fluke in all voltages, current ranges and resistances I checked. Honestly even if this meter is out of calibration spec, it is still orders of magnitude more accurate than I need.After using it for a while to compare measurements I ran a self test again and it passed with no error codes. I repeated and gave faults for 100.2 and 302.2 only. So its probably a borderline issue with something, thinking it out of spec voltage or some ripple/noise getting through.I will start probing voltages and see if there is anything obvious going on there. If anyone familiar with these meters has any suggestions I am all ears.