21 Sep
2011
21 Sep
'11
10:52 a.m.
I replaced all the mains filtering capacitors in the
original DEC GIGI
power supply when one blew only to find that the power supply lasted
another 10 minutes before losing power completely. At this point I
decided given the relatively standard power outputs (5V 3A, 12V 1A, -12V
0.3A) I would source a replacement power supply.
And thus end up with something which in not a GIGI. OK, it performs just
like one, but it's not original. Yes, I do regsrd the PSU as being part
of the design.
Amazingly, there's a schemtic of the PSU in the technical manual on
bitsavers (it's the only part that does get a full schematic). It looks
to be a conventional SMPSU, and shouldn't be hard to fix (famous last words).
This arrived and was installed yesterday. It I guess unsurprisingly is
substantially smaller and lighter than the original. The original
cooling fan was removed as it was basically transformed directly from
either the mains directly or one of the windings of the main
The schematic seems ot imply there are 2 identical fans which are
connected in parallel across 120V mains or in series across 240V mains.
transformer. I used the fan out of an external SCSI
enclosure as a
Hang on. Do you have a mains-frequency trasnformer? If so, it's not the
PSU shown in the manual, but one that's probably a lot easier to repair.
-tony