DEC H7260 PSU fault
jules.richardson99 at gmail.com
Thu Jan 25 17:06:56 CST 2018
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.
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.
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 ;-)
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