Fire-Sale PDP-11 update (and request for parts)

Josh Dersch derschjo at
Sat Dec 5 00:41:32 CST 2020

Thought you folks might be interested in a quick update on my folly here.

At the beginning of November I drove down to the bay area to pick up the
two fire-damaged PDP-11 systems -- a PDP-11/70 and a PDP-11/45.  (I also
made a few other stops and got a few other items, but that's not what I'm
here to talk about...)

Over the past few weeks I've gone over the two systems and my assessment is
that the 11/70, while completely filthy, is completely restorable.  The
fire/heat damaged the front panel enough to discolor the plexi and start
melting a few switches (
but that's the extent of the damage.  My only fear is that the fingers on
the backplanes might possibly have some corrosion here and there, but I've
started going through and cleaning the boards and the backplane slots and
so far I haven't run into anything that looks troubling.

The 11/45 is considerably further gone.  It took a serious amount of heat,
enough for the pig iron frame for the front panel to start melting (  The front panel is
completely destroyed, as is the wiring harness for the power distribution.
But... the metal of the chassis and the power supplies seems to have
protected the boards and the backplane.  There are no melted or even
discolored wire-wrap wires on the backplane, and the boards look fine.  As
an experiment I took the non-11/45-specific boards out of the backplane (a
Plessey memory board, an RL11 controller, and an M9301 bootstrap terminator
-- this one was right up front where things were the hottest and the
handles had started to melt) and tested them in my PDP-11/40.  They all
work fine.  So I think that, maybe, with a LOT of effort, the 11/45 could
live again.

I'm tackling the 11/70 first (Al kindly sold me a new front panel for a
very reasonable price so it already looks 100% better) and once I'm done
with that I hope to move on to the 11/45.  In the meantime I'm hoping to
keep my eyes peeled for parts for the /45.  I found a seller on eBay with
"restored" H7420a power supplies for $68, with free shipping so I grabbed a
pair.  I realize this is unlikely, but I was curious if anyone has 1) any
parts of the 11/45 power wiring harness, or 2) (really unlikely) an 11/45
front panel in any condition.  Well, any condition better than "melted into
slag," I suppose.  I can build my own wiring harness, but if I can save
myself the trouble, that'd be nice.

- Josh

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