April 17, 2021 Repair, Test Equipment

Keithley 196 - Electrolytic capacitor replacement

Replacing the electrolytic capacitors in a Keithley 196 system dmm

Keithley 196 - Electrolytic capacitor replacement

It is time to replace the electrolytic capacitors on my Keithley 196 multimeter. One capacitor has already failed (-15V rail). Judging from the date codes on the chips my unit is a late 1986 model (35 years old at the time of writing!).

Here is the list of capacitors to be replaced:

Designator Description Digi-Key part no.
Display Board
C1 10μF, 25V 493-13463-1-ND
Main Board
C101 10000μF, 25V 493-7297-ND
C102, C104, C107, C108, C127, C140, C147 10μF, 25V 493-13463-1-ND
C103 1500μF, 25V 493-15301-ND
C105, C106 620μF, 35V P14940-ND
Analog Board
C33 10μF, 25V 493-13463-1-ND

Some of the capacitors I chose are overrated but since I had other instruments that needed capacitor replacement I grouped them together. The dimensions are OK though. It is now ready to work for at least 20 years more.

There is also a 15μF tantalum capacitor (C44) in the analog board that may eventually fail. It is used as the input filter capacitor for the AD637 RMS converter. But I'm going to leave it be.

Here's a long boring video of the replacement. Enjoy!