DEC PDP-8/e H212 core mat repair

Toby Thain toby at
Mon Jul 19 17:16:28 CDT 2021

On 2021-07-19 6:06 p.m., Rod Smallwood via cctalk wrote:
> Yes most core stringing was outsourced.

There's more detail on early core production in the book "IBM's Early
Computers", iirc. (And possibly "A Few Good Men From Univac".)

> ...
> Rod Smallwood   -- Digital Equipment Corporation  1975 to 1985
> On 19/07/2021 22:50, Jules Richardson via cctalk wrote:
>> 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.
>> Jules

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