31 Aug
2014
31 Aug
'14
2:51 p.m.
On 31/08/2014 16:53, Robert Jarratt wrote:
I have compared a known good PSU with the bad one and
I can see that all the outputs from the PSU, including P OK and DC OK are shorted to
Common, whereas on the good one they are not. Any suggestions where to start looking in
that case?
I can think of three possibilities (all on the output side of the PSU):
- Failure of the over voltage crowbar circuit
- Shorted rectifier diode
- Shorted capacitor
I'm surprised you didn't get the clicking sound from the PSU as it tries
to recover from over current. I had a PDP-11/84 with a shorted rectifier
diode that did this a few years ago.
I haven't had chance to look at my H7864 yet but for this kind of
problem I would start by removing the main output capacitor and checking
if the short still exists. If that was OK then I would remove the
rectifier diodes and so on.
Matt