PDP-8 core memory problems.
elson at pico-systems.com
Mon Sep 5 16:21:27 CDT 2016
On 09/05/2016 01:59 PM, Mattis Lind wrote:
> I have now concluded that the fault is in the core memory module itself.
> The sense winding is broken on bit plane 7.
Have you actually ohmed out the sense/inhibit wire? There
were some very old memories that had some kind of
metallurgical problem where the wires corroded away, but not
heard of DEC cores being prone to that.
3D core stacks have combined sense/inhibit wires, and there
is usually a pulse transformer between the sense amp/inhibit
driver and the wire itself. Also, if the bit 7 inhibit
driver has a blown transistor, it could cause the sense amp
to be shunted or overloaded. I'd check all the associated
sense/inhibit circuitry before assuming it is the plane.
(Of course, you may have already done all this by swapping
boards, etc.) A blown inhibit driver could take out the
pulse transformer, too.
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