I’m repairing a Keithley 237 High Voltage Source. In the output stage there are several of these rectangular metal modules. Each one has a pin on the left and right side, plus multiple pins on the bottom (I don’t know the exact number). The body seems filled with resin visible at the edges.

The marking on top is: '108D - 1A11N4 - 60'.

This unit delivers very precise high voltage (up to ~1000 V) and current control down to ~200 nA. The design dates back to the 1980s and has been kept mostly unchanged.

 

I’m repairing a Keithley 237 High Voltage Source. In the output stage there are several of these rectangular metal modules. Each one has a pin on the left and right side, plus multiple pins on the bottom (I don’t know the exact number). The body seems filled with resin visible at the edges.

The marking on top is: '108D - 1A11N4 - 60'.

This unit delivers very precise high voltage (up to ~1000 V) and current control down to ~200 nA. The design dates back to the 1980s and has been kept mostly unchanged.


View attachment 356940

View attachment 356941

Looks like they're high-voltage reed relays. FWIW, you can review the repair manual yourself here.

 

Even without the manual, the metallic housing and axial leads entering a glass envelope reveals they are SPST reed relays.

They are selecting current limiting resistors, apparently varying the output.

 

Looks like they're high-voltage reed relays. FWIW, you can review the repair manual yourself here.

Thank you very much, with the schematic it will be much easier!