25 Jan
2018
25 Jan
'18
11:30 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Glen Slick
via cctalk
Sent: 26 January 2018 01:17
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: DEC H7260 PSU fault
On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk
<cctalk at classiccmp.org> wrote:
If the door is open the fans run full blast.
Hi all,
I mentioned this in the thread where I'd asked about basic Microvax II
info, but it may have got lost in traffic...
The machine's H7260 PSU is somewhat unwell - one of the internal
+5/12V supplies appears to be healthy, but the other has outputs which
are sitting at around 2.5V (both on the 5V and 12V rails) under a test load.
Previously you also said:
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 forget what the card-cage door interlock switch does, whether it prevents the
power supply from fully powering up, or if the power supply does fully power
up but also turns the fans on full blast if the card-cage door is open which
disrupts the normal cooling airflow. I would check what my BA123 does, but that would
require too much moving of
stuff about at the moment to get working space around it.