DEC H765 line interference caps

Fritz Mueller fritzm at
Tue Dec 22 18:12:54 CST 2020

Hi all,

I’m just starting in on a PDP-11/34 for a friend (happy holidays!)  I currently have the H765 power supply torn down for cleaning, inspection, and testing as a first step.

While I have the transformer out on the bench, I’m wondering about the line interference supression caps on the “CAP MOV” board attached to the transformer.  These are CDE 220 VAC .1 MFD, across the line, in parallel with some metal oxide varistors.

Drawing on collective experience here: would I be well advised to go ahead and swap these out for some modern X2 safety caps while I have the supply apart?  Or are these in the “oh those are rock solid; I wouldn’t touch em unless they were faulted” category?


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