> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Jules > Richardson via cctalk > Sent: 25 January 2018 23:07 > To: xx Classiccmp mailing list <cctalk@classiccmp.org> > Subject: DEC H7260 PSU fault > > 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. > > Initial questions... > > 1) Are schematics are available online? I couldn't find them (either under the > DEC p/n or the Astec AA13010 one), but perhaps they're buried in schematics > for a specific DEC machine somewhere. >
I doubt it. For the H7864 from the BA23 MicroVax II Enclosure I couldn't find anything and in the end made my own schematic. > 2) Upon initial glance, the 'first' board of the three in the PSU module appears > to be a pair of control relays, bridge rectifiers and capacitors, supplying +/- DC > voltages to the two individual PSU boards. Does anyone know if I can disconnect > these from the PSU boards safely* and measure their outputs, and if so what > voltages I should expect to see? That might be a good initial test before > pointing a finger at the PSU board associated with the low outputs. > > * I mean without component damage - I expect they might be sitting at a > significant DC voltage, so there's an obvious personal safety aspect too ;-) > > cheers > > Jules
