PDP-8 core memory problems.
elson at pico-systems.com
Mon Sep 5 17:39:18 CDT 2016
On 09/05/2016 05:26 PM, Mattis Lind wrote:
> måndag 5 september 2016 skrev Jon Elson <elson at pico-systems.com>:
>> 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?
> Yes. I have measured at at the tabs where the red arrow points in the image
> Unfortunately I am pretty sure that this will rule out pulse transformers
> or whatever.
Ugh! That could be messy. DEC later went to planar
memories, for obvious reasons. Yes, these built-up core
stacks could be hard just to open up to get to a single
plane. IBM, CDC and others all made them like this in the
60's before realizing how hard that made the job of testing
and repairing. (I guess the shrinking of the cores is what
really made the planar core boards practical.) Well, unless
there is a spare plane in the stack, you can't break it too
much more than it is broken now! But, really, if one of the
wires has failed within the plane, it could be just about
impossible to fix. If it is a break outside of the core
matrix, that wouldn't be hard to fix, unless the wires have
become brittle over time, in which case any manipulation
would just cause more damage. GOOD LUCK!
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