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 

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