26 Jan
2018
26 Jan
'18
5:15 p.m.
On 01/25/2018 09:29 PM, Jules Richardson via cctalk wrote:
On 01/25/2018 07:16 PM, Glen Slick via cctalk wrote:
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
On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson
via cctalk
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, 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.