Keithley 237

[Mrusseau]

I have a Keithley 237 that has a strange problem. I fixed the +/-30V supply (dry voltage doubler caps). In the I Source V Measure mode it is in tolerance for all current ranges except the 10mA range. Has anyone seen this before? I have schematics but it's not really clear the path of the current flow for that range. Also, the unit reboots on occasion.

[coromonadalix]

Can you post a link to the schematics you have ?  is it this one : http://www.ko4bb.com/manuals/104.157.197.231/Keithley_236_237_Source_Measure_Unit_SMU_Service_Manual_and_schematics.pdf

I only saw the 236_902_01D.pdf   document ?  no schematics in it,  but there is an brief description of the voltage and current feedback circuits, maybe you have some switching section errors ?

And a thread for the 236 :
https://www.eevblog.com/forum/testgear/keitley-236-teardown-and-review/msg791944/#msg791944

The first link seems very complete
You have to check all the voltages if they all are in compliance,  careful you have an +/-1200 vdc section (page 129)     

Maybe some gentle taps on the cpu section could tell you if you have cold solder joints who reset the cpu