PDP-8 core memory problems.

Anders Sandahl anders at abc80.net
Tue Sep 6 12:32:45 CDT 2016

> So what are the other options?
> * Trying to repair the unit. Every plane is soldered together with the ones
> nearby to convey the X/Y signals. This can probably be undone with a
> patience and soldering braid. But what are the chance that the X/Y wires
> gets lose then? Are those soldered or welded into place?
> Then it would be quite tricky to just identify where it is actually broken.
> Any ideas for how to do this? A microscope of course. Any other ideas?
> Applying an electrical field between the wire and something else and try to
> detect it?
A stereoscopic microscope and a lot of patience is a good staring point.

> Repair. If the wire is broken in the mat it is probably not to difficult to
> pull out the broken parts. But then the new wire has to be spliced in. What
> is t he best technique to do that?
> How to push in the new wire in the matrix? I now that Anders was able to do
> this with a broken X-wire in a PDP-8/L stack.
I used a pair of tweezers to push the new thread in, one core at a time. 
You should try to change as small part as possible. I just changed the 
thread thru the first 64 cores, then I joined the two threads together 
in the middle of the core plan. I then used nail polish as an isolatur.

I didn't thought I had something to lose to try to repair the existing 
core stack. Without it the computer is really not working at all. I'll 
think you should try to repair it. Start to bring out the core stack 
and  then turn it around for a while until you are brave enough.

I found some pictures on stacks to the 8/L in pieces before I started on 
the internet, that helped me to understand what I had to master.


More information about the cctalk mailing list