H7874 power supply

Robert Armstrong bob at jfcl.com
Sat Mar 28 20:28:54 CDT 2020

  Does anybody have a maintenance print or service manual for the DEC H7874?
This is the power supply used in the BA4xx and R400x cabinets.  As you might
guess, I have one that tries to power up but shuts down after a second.
Probably a bad capacitor (or several), but this thing is ridiculously
complicated and not all that easy to disassemble, either.  I'd like to be
able to trouble shoot it rather than just firing the proverbial parts cannon
at it.  FWIW, none of the electrolytic (of which there are many) have
obviously failed - no leaking, no bulges, etc.  Of course, that proves
fairly little.



Bob Armstrong


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