PDP-11/23 Debugging

Noel Chiappa jnc at mercury.lcs.mit.edu
Fri Nov 7 15:48:37 CST 2014

    > From: Ben Sinclair

    > Then, in between trying a few things (but without touching the
    > hardware), the machine seemed to get very flaky.
    > ...
    > I tried removing the RLV11 boards, returning the machine to it's former
    > state, but I have the same issue.

This is a total _guess_, but... I've recently been working with some 11/23's I
just bought, and I too had similar flakies appear mysteriously with one of

I'm not sure exactly which of the below finally cured them, but you can try
the following things (one of which finally did it for me - after sitting for
a long time, the connections can possibly be slightly flaky):

- re-seat all the cards in the backplane
- re-seat the chips on the CPU card (take them out _very_ carefully, slowly
	levering from all 4 corners - they are brittle, and you can fracture
	the carrier if you get too aggressive)
- re-seat all the jumpers on the CPU card

I also discovered and repaired at least two cold-solder joints (one was one of
the pins for W1, the master clock control - the pin was actually loose when I
wiggled it). Cold solder joints are pretty insidious - they can work fine for
a while, and then start to give problems.

Do you have more than one memory card that you can swap in/around? That
might be it, too.


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