PDP-11/23 Debugging

Ben Sinclair bensinc at gmail.com
Fri Nov 7 16:04:16 CST 2014

Thanks, I'll try those suggestions!

I'm actually on my second memory board. I just never got it to boot with
the first board, so I ordered a new one on a whim that worked. I did find
another cheap M80186, so when that arrives I have a spare to try swapping.

On Friday, November 7, 2014, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:

>     > 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
> them.
> 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.
>         Noel

Ben Sinclair
ben at bensinclair.com

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