4 Dec
2020
4 Dec
'20
10:41 p.m.
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 (http://yahozna.dyndns.org/scratch/1170/1170.jpg)
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 (
http://yahozna.dyndns.org/scratch/1170/1145.jpg). 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
5 Dec
5 Dec
2:19 p.m.
On Dec 5, 2020, at 1:41 AM, Josh Dersch via cctalk
<cctalk at classiccmp.org> wrote:
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...)
...
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 (
http://yahozna.dyndns.org/scratch/1170/1145.jpg).
It looks pretty bad, but it's not quite as bad as what your words suggest. I doubt
that frame is iron. Consider that the rails of the rack are corroded but not visibly
warped, let alone melted.
I would guess the bezel is potmetal or some other low melting point cheap alloy. Potmetal
is a zinc alloy, it melts very easily.
paul
6 Dec
6 Dec
3:11 p.m.
On Dec 4, 2020, at 10:41 PM, Josh Dersch via cctalk
<cctalk at classiccmp.org> wrote:
I realize this is unlikely, but I was curious if anyone has 1) any
parts of the 11/45 power wiring harness... I can build my own wiring harness, but if I
can save
myself the trouble, that'd be nice.
Yeah, I had build my own for my /45 restoration. It wasn't all that bad. Throw down
for a nice ratcheting single-gesture crimp tool for the job and you'll be glad that
you did :-)
I found wirebarn.com had a nice selection of wire available in less-than-full-spool
lengths, and most of the original colors. I may have had to fill in a few things from
other suppliers (I found it helpful to stick to the original color coding.)
Another tip is that the wire list you see in most of the /45 drawing sets is actually for
the power harness, and not the backplane. The wire lengths in that list were useful; I
cut to those lengths, then started on the regulator side of the harness, installed in the
machine, and bundled and trimmed to length as I worked my way down the backplane. In the
end I had a reasonably neat fit and very little wasted wire.
I had the extra wrinkle of having the earlier (serial # <2000) power distribution
system in my /45 (IIRC the wire list was from the newer system, but it wasn't too hard
to adapt it.)
Do you have the springy steel strip that supports the harness between the moving and
stationary parts of the cabinet? That may require some fab or improvisation if not. I
had one left over from an 11/40 that I was able to make work well enough with my older
style cabinet.
cheers,
--FritzM.
9 Dec
9 Dec
10:48 a.m.
On Sun, Dec 6, 2020 at 3:11 PM Fritz Mueller via cctalk <
cctalk at classiccmp.org> wrote:
Thanks, that'll be handy.
On Dec 4, 2020, at 10:41 PM, Josh Dersch via
cctalk <
cctalk at classiccmp.org> wrote:
I realize this is unlikely, but I was curious if
anyone has 1) any
parts of the 11/45 power wiring harness... I can build my own wiring
harness, but
if I can save
myself the trouble, that'd be nice.
Yeah, I had build my own for my /45 restoration. It wasn't all that bad.
Throw down for a nice ratcheting single-gesture crimp tool for the job and
you'll be glad that you did :-)
I found wirebarn.com had a nice selection of wire available in
less-than-full-spool lengths, and most of the original colors. I may have
had to fill in a few things from other suppliers (I found it helpful to
stick to the original color coding.)
Another tip is that the wire list you see in most of the /45 drawing sets
is actually for the power harness, and not the backplane. The wire lengths
in that list were useful; I cut to those lengths, then started on the
regulator side of the harness, installed in the machine, and bundled and
trimmed to length as I worked my way down the backplane. In the end I had
a reasonably neat fit and very little wasted wire.
Also very good to know, thanks!
I had the extra wrinkle of having the earlier (serial # <2000) power
distribution system in my /45 (IIRC the wire list was from the newer
system, but it wasn't too hard to adapt it.)
Do you have the springy steel strip that supports the harness between the
moving and stationary parts of the cabinet? That may require some fab or
improvisation if not. I had one left over from an 11/40 that I was able to
make work well enough with my older style cabinet.
I do, it's a bit rusty. What remains of the wiring harness is no longer
attached to it, as the plastic ties holding it in place burned away (along
with the rubber sheathing and the most of insulation on the wires
themselves.)
- Josh
cheers,
--FritzM.
1473
days inactive
1477
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