What is the best way to fix a wire wrapped backplane?
I have a pdp-11/40 with a short to ground in one of the backplane runs.
I probed the backplane with a wooden stick and with some wire tyes and
the short went away. I have a pretty good idea which segment of wire is
the problem. I have probed the area again and I can't get it to come
back. So, what should I do?
1. Be happy it is working. Note the problem in my log book. Wait for it
to happen again.
2. Replace that run in the backplane.
I figure I will have to replace most of the run because this segment is
on the lowest wrap level and in the middle of the run, so I have to
replace this one and the ones on either side.
I have done some wire wrapping, but this thing is very intimidating.
Replacing the wire is easy, but I am afraid that taking out the old ones
will create another problem. These backplanes have the wires pretty
taught and they are pulled over square edged pins. How fragile is the
backplane wiring?
If you have a PDP-11/40 then the KM11 is your friend. I have been
troubleshooting this problem for a while, but after I handbuild a KM11
(from Tony Duell's notes), the problem was obvious.