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

Josh Dersch derschjo at
Wed Dec 9 12:48:13 CST 2020

On Sun, Dec 6, 2020 at 3:11 PM Fritz Mueller via cctalk <
cctalk at> wrote:

> > On Dec 4, 2020, at 10:41 PM, Josh Dersch via cctalk <
> cctalk at> 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 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.)

Thanks, that'll be handy.

> 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

- Josh

>    cheers,
>      --FritzM.

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