24 Jul
2013
24 Jul
'13
11:27 a.m.
But you can run the PSU without most of the boards in
place, it needs some
load but not all the boards.
Actually, Iv'e yet to find one that will not run OK with no load at all.
If it does need a load I'd rather use a 6V bulb than a part-set of HP9830
boards :-)
Incidentally, yuo do not have to screw the PSU heatsink to the chassis
for testing. Yes, if the machien is being rund for a longish time you
should -- it's part of the heatsink for the power transitors on the PSU
board. But for tesitng it will not overheat without being screwed down.
[...]
In my experience the 74121 and 74123 have a high
failure rate, but it's also
a good idea to check the ESR values of the surrounding cap's (tantalium and
elco's).
My expeirience is tha the most unreliable pwats in an HP9800 re the 74Hxx
ICs. But those can't be the fault here.
-tony