8 Jul
2011
8 Jul
'11
6 p.m.
Taken all the cards out and given it a good clean.
Checked for any odd
washers etc. in the backplane.
Removed the power supply (H786), hooked up to a pair of hard drives as a
dummy load and tested. Nothing. Normally at this point I'd scrap it and
hook up a PC PSU but I've been reading this group too long and have been
persuaded by Tonys component level repair arguments so I got stuck in :)
With a comment like that, how can I avoid tryign to help :-)
Tracked it down to one of a pair of 1N4004s connected
in series after
the 7912 12V start-up regulator. So, I now have healthy 5V & 12V
I have the MINC printset to hand, open t the H786 PSU diagrams. I assume
these are D31 andD32 on the 'Master Board'. I thimk the current fault
migth be in taht area too.
supplies and these seem to be stable for a long time
with all the cards
in place.
But - it's not booting. The diag LEDs on the BDV11-YA constantly read
1001 from power on (I'm assuming that on=1). The only table of diag
codes that I could find lists 1001 as "DECnet message received" which I
believe to be bogus since I don't have any DECnet cards (I'm also
wondering if the MINC has different diag codes?). So I started digging
further and found that BDCOK H is ~1.7V and BPOK H is ~2V. Now, I
I was going to ask if these signas were, in fact, oscillating, but I
noticed your next message whre you say theu are/ Are you sure it's 50Hz,
though? 100 Hz would be more likely.
Anyway, I'd check th bridge rectfier diodes D1-D4 ontne Master Board
(particularly if it really is 50Hz) and the capacitor C3 (2100 uF) at the
input to the 7812 yuou mntion. A 220uF will be fine as a repalcement.
-tony