20 Nov
1998
20 Nov
'98
4:59 a.m.
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were attached to the frame, and the needles withdrawn.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