Early PDP-11/45 backplane SPC power
Fritz Mueller
fritzm at fritzm.org
Tue Jun 28 11:33:01 CDT 2016
So, after finding that a DL11-E wasn't working in the backplane SPC
slots (26-28) on my 11/45, I took a closer look. The problem isn't
exactly what I had expected -- -15V seems to be distributed there, but
+15 is not.
Looking closely at the print sets, the listed configurations only
mention DL11-A, the 20ma current loop model, which wouldn't require +15
to work. I wonder if some +15 distribution wires were added in an ECO,
or maybe EIA console from the backplane SPC slots was never supported
for these early 11/45s (mine is serial 152).
There's one other oddity -- the power distribution table in
EK-11045-MM-007, page 510, implies that +15 should be distributed to the
SPC slots on CA1. I'm wondering if this is a typo, since I'd expect
that pin to be NPG? The DL11-E looks to be expecting +15 on UA1 in any
case.
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