> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@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@classiccmp.org> > Subject: Re: DEC H7260 PSU fault > > On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk > <cctalk@classiccmp.org> wrote: > > 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.
If the door is open the fans run full blast. > 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.
