DEC PDP-8/e H212 core mat repair

Jules Richardson jules.richardson99 at
Mon Jul 19 16:50:10 CDT 2021

On 7/19/21 3:40 AM, Joshua Rice via cctalk wrote:
> I believe much of the core manufacturing for DEC minicomputers was 
> outsourced, but a lot of it had become much more automated by the late 60's 
> and early 70's.

I've got a trio of planes here, two of which are from a Lockheed MAC-16, 
but the other one is made by Keronix out of Santa Monica for an unknown 
machine (dated 1973, model number "P4" and p/n 816335 if that means 
anything to anyone, approx 16"x16" with two 100-pin, double-sided finger 
edge connectors on 0.1" spacing).

Anyhoo, the Keronix one has a sticker on it saying it was repaired by DMA, 
inc. in Amery, WI in 1980 - which might suggest that there were third 
parties around working on boards, rather than them having to go back to the 
manufacturer for repair. (I have no idea what the nature of the repair was, 
of course; maybe it was to surrounding logic rather than the mat itself).

> It's worth noting that most computer manufacturers appreciated the 
> fragility of core memory planes at the time, with most of them being 
> protected with either PCB's or perspex/plastic shields on top of the core 
> planes.

Yes, that's how all the ones I've ever seen have been. The Keronix one has 
an additional shield over the top of the entire PCB, on top of the one 
protecting the cores.


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