DEC H7822 power supply

Peter Coghlan cctalk at
Mon May 2 09:58:07 CDT 2022

I wrote:
> At least the H7822 does not seem to suffer from the leaky capacitor problem
> like the H7821 does.

Well, it's made a liar of me already.  While checking over my previous work
replacing the zener diode to make sure I didn't break something else, my
eye was drawn to a ring of sticky brown goo around the base of one of
the capacitors that looks the same as the ones that leak in the H7821.
Thankfully, it doesn't seem to have been there long and didn't get a chance
to spread around the board.  Bizarrely this capacitor has it's legs pointing
upwards and managed to leak while there are similar capacitors on the other
board with their legs pointing downwards which don't seem to have leaked (yet?).

When I compare them side by side, I can now see that the upper board in
the H7822 is identical to the single board in the H7821.  It seems that
the lower board in the H7822 is only responsible for powering the front
disk drive connector which I found to be independent of the other supplies.

Peter Coghlan.

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