Core planes

From: Ethan Dicks <erd_at_infinet.com>
Date: Fri Nov 20 12:59:54 1998

>
> The row/column drive line insertion was eventually automated, although
> amazingly enough there was a period of time for which manual assembly was
> less expensive than automatic assembly.
>
> The cores were poured onto a metal plate with indentations where they were
> supposed to reside. Each indentation had a pinhole through which a vacuum
> pump provided suction to keep the cores in place. The plate was vibrated
> until all the cores were properly seated.
>
> Once the cores were corrrectly positioned, long hollow needles with wire
> threaded through them were driven through the rows (or columns). The wires
> were attached to the frame, and the needles withdrawn.
>
> AFAIK, however, the sense lines were still threaded by hand.

My first core stack is in need of repair - a 13-bit PDP-8/L stack made
of 3 panels of 4 planes and one panel with 1 plane (parity). I got the
machine in high school - it was defective, so I cut apart the wires
holding the planes together. There are several dozen broken cores on
a couple of the planes. I have always contemplated repairing it, after
all, what can I do, break it? With no source of replacement cores, I was
considering scavenging the parity plane. If someone had a similarly broken
PDP-8/L or PDP-8/i core stack I would love to sort the planes for three
good panels. I do not relish the thought of threading the sense/inhibit
wire through 4096 cores. Does anyone have any idea as to the wire diameter?
(In case I can't remove and reinstall the same wire)

One problem I had when disassembling it was that the PCB material is
very temperature sensitive. It blisters under a normal iron. I tried
to desolder the top plane and did a bit of damage to the diode-matrix
board.

-ethan
Received on Fri Nov 20 1998 - 12:59:54 GMT