[Info-vax] SBB power supplies failing slowly

[Jan-Erik Söderholm]

Den 2022-03-28 kl. 11:24, skrev Phillip Helbig (undress to reply):
> I've seen this before, about a year ago, then it happened again in
> another BA356: Disks go offline and into mount verification, then come
> back after a minute or so.  The process repeats every ten minutes.  Of
> course, being VMS, the cluster continues and practically nothing else is
> affected, but it is annoying.
> 
> Replacing the power supply solves the problem.
> 
> I understand that a power supply can fail, but why is it failing in this
> manner?  Maybe overheating and shutting off then coming back on?
> 
> Being VMS, I dismounted the shadow-set members in the box with the flaky
> power supply.  Thanks to minicopy, things were quickly back to normal
> after replacing the power supply.  To do that, I turned off the box,
> replaced the power supply, and turned it back on.  The node whose
> system-disk shadow set was in the box didn't crash.
> 
> I like VMS.
> 
> Now to find a few more replacement power supplies.  When collecting
> SBBs, I concentrated on disks, and I think that I have enough of them.
> Since the first power-supply failure wasn't until about a year ago, I
> hadn't explicitly looked for them, but fortunately got a few with BA356
> and other SBBs (mostly disks).
> 
> I need the Top Gun Blue (that's really the official colour!) 180W
> versions.  If anyone has any in Scandinavia, Germany, Benelux, England,
> Switzerland, Austria, Slovenia, or northwestern Croatia I could probably
> collect them sometime this year, probably before autumn.  Rest of the
> Balkan: next year.
> 
> I also plan to be in the southeast USA soon so would be happy to collect
> there as well.  (Apparently they run on 50 or 60 Hz and anything between
> 100 and 240 volts.)
> 
> It's mainly the power supplies I need, but I'll take any blue SBBs.
> 

PSUs are aging. The electrolytic capacitators are drying out. This will
make the voltages to become more unstable and causing intermitent
issues before going totaly "off". Quite normal, I'd say.

Some makes a buiness out of replacing old capacitors in power supplies
for TV sets and other home/kitchen appliences. I guess that is equially
possible in these PSUs. They are not too modern and should be fine to
work on without special soldering equipment.