On 01/25/2018 09:29 PM, Jules Richardson via cctalk wrote:
On 01/25/2018 07:16 PM, Glen Slick via cctalk wrote:
On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk
OK, the top PSU of the pair in this machine appears to be healthy. The
bottom one, however, sits at around 2.5V on both the +5V and +12V outputs.
That's without any cards, and the card-cage fan / temperature sensor
unplugged, i.e. just with my dummy loads in place, so it looks like that
PSU
has issues (oh, and I tried decoupling the PSU from the backplane and
loading it via the drive connector, so it doesn't appear to be a backplane
issue).
Looking here at page 107 of the maintenance print set, BA123-A Basic
Enclosure Power Harness Wiring Diagram
http://www.bitsavers.org/pdf/dec/vax/630/MP02071_630QB_Mar85.pdf
Did you disconnect the wiring harness from J10 completely? If you
disconnected the temperature sensor module or the card-cage door
interlock switch I would expect that the power supply might not
operate normally.
I believe that I tried it both connected and disconnected, with no change
in behavior, but I'll double-check (not until tomorrow evening now, though).
OK, I just verified that - it doesn't matter whether the J10 harness is
connected or not, same behavior.
The outputs of the main relay/regulator board which feeds both supplies
appear to be the same, so I don't think that's at fault. I think my next
step is to trace out the wiring for the temp sensor, along with that fourth
"fan control" PCB within the PSU module so that I can better understand
what it's trying to do.
After that... well, I need to work out how to get the entire supply
assembly to start up while it's open, so that I can work on it outside the
machine - then I can at least start looking for differences between the two
supplies (boy, are those things complex, but maybe I'll get lucky and it's
a bad solder joint or cap somewhere)
cheers
Jules
