Hello everyone, I just acquired a Keithley 617 Electrometer. I got it very cheap from the Physics lab at University, they were going to throw it to the garbage. The unit seems in fairly good condition besides being a bit off and requiring some calibration. There is a couple of things I'm concerned about though.
1. Dave made a teardown video of this device and there are some differences in the Analog front-end as can be seen on the picture. The first are the relays. Mine is equipped with COTO read relays instead of the rectangular relays which just means that this is probably either an older or more recent revision. My concern is with the input dual JFET which doesn't have the clip with the guard wire. On the component it is written 9446-TM LS. I wasn't able to find anything about it and the manual, at least the one I have, only refers to this component as Q308. I'm actually concerned the unit may have been tempered with.
2. The device is slightly out of spec on most ranges and needs calibration. It's not a big deal but something funny happens when measuring resistors between 20k and 30k. I connected the input on a GenRad 0.01% decade resistor box and when I go from 10k to 20k, the display starts flashing displaying 8.52K. I can hear a relay clicking continuously. This continues when I go to 30K the only difference being it then displays 16.16K. Once I get to 40k, everything goes back to normal. From there, if I go back to 30K, everything is just fine and if I continue to 20K, everything is still fine. Non of this happens if I disable auto ranging. It's like the auto ranging algorithm cannot decide which range to use and enters a loop. Has anyone seen that kind of behaviour before ? Maybe it will be fine when calibrated ...
For more reference, the Analog board has the following number: 617-162-02L and the logic board has the following number: 617-102-026. Also, the date code on the Nichicon electrolytic capacitors are all H9446 which means they have been installed in 1994.