Subject: Mouse Pissed! Need power supply help
From: Charles <charlesmorris at direcway.com>
Date: Wed, 23 Nov 2005 10:51:33 -0600
To: cctalk at
classiccmp.org
I've found the reason why my PDP-11 power supply (H7861) is not
putting out POK and DCOK signals. One of the small daughterboards
which appears to provide the level checks and timers (marked
Digital Type 1 SG-1 5015047B 5415048) has been badly mouse-pissed
and rusted. (Previous owner stored it in the carport).
There is enough corrosion that the leads of two diodes and two
film resistors have been rusted right through and broke off during
gentle toothbrush cleaning, and several others don't look good. I
suspect the board would be better replaced than patched.
Unfortunately the H780 schematic does not match closely (they use
74123's while this one uses 555's, for example) so it'll be hard
to figure out the missing or unreadable parts anyway!
Does anyone have a spare board from a "parts" power supply?
Or at least a schematic?
thanks
Charles
Your best bet is to scrounge a power supply as they can be had.
The H786 and H7861 are interchangeable, not the same circuit but
fit the same form factor. A H780 can be used but it's not a
mechanical fit.
Allison