30 Mar
2020
30 Mar
'20
7:17 a.m.
Looks like for this enclosure an ATX supply could well
work.
For my VAX my notes say it didn't.
A VAX would certainly be harder. You'd have to kludge up the ACOK and DCOK signals
for one thing, which I don't think the R400x uses. It'd be really handy to find
even a schematic for the backplane so we could see which signals are actually connected,
but I did some searching and came up with nothing.
Oh, and I did try to power up the H7874 on the bench for testing, but it wouldn't
turn on there either. It probably has a minimum load requirement, or it needs some signal
from the backplane to turn on. FWIW, the R400x does not have a power switch - the only
way to turn it on or off is thru the H7874, either by the circuit breaker or the power
control bus. The R400x also has several large power resistors on the M7493 SCSI connector
module; those may be there to provide a minimum load for the power supply.
Bob