I have just collected a MicroVAX II which has been in storage and has not
been powered on for 20 years. This is my first machine of such an age,
unfortunately I am not particularly knowledgeable at the electronics level
(I studied circuits academically 25+ years ago and can solder a bit, but
that is as far as it goes). I know I will need to treat it carefully in
order to get it working again. I plan to open it up and make sure I clear
out any debris etc, but beyond that I need advice from those with the
experience and knowledge that I lack on how to go about powering it up
carefully.
IMHO the most important thing to do after checking for obvious problems
-- loose parts, evidence of overheating/burning, etc, is to test the
power supply (PSU) on a dummy load. A defective PSU could wipe out every
chip in the machine!.
Since you're happy to dismantle the machine anyway, this should be quite
easy. With all the PCBs out of the backplane (make notes/diagrams as to
what goes where), and with the power cables unplugged from the drives,
connect a 6V car bulb between the +5V line and the 0V line (you can find
these by tracing back from the known Q-bus pinouts if you can't find them
any other way) and power up. Mearue the 5V line with a voltmeter, and if
possible the other power lines (if you can find them). Only when you know
they're correct should you plug the logic boards in.
Oh, I would recomend opening up the PSU (mains disconnected, of course),
and looking for signs of trouble in there. And check all the fans are
rotatig when you turn it all on
-tony