Assuming people are still interested I'm working on other, lesser issues
now that the little thing works.
First thought: The interconnections between the CPU board and the IO
board/memory boards are weird. Basically it's a plate, insulator, board,
very odd spacer that provides interconnection, bottom board, insulator,
plate, and the bottom hinge that holds the cpu board above the floppy
controller board.
These interconnections are very sensitive to torque. Make sure all
screws are snugged down and all the bolts on the bottom (6) secure the
screws to the bottom hinges. Otherwise torque will cause the
interconnection to be intermittent and you'll go crazy trying to
troubleshoot.
Another odd issue: When I have the top CPU board vertical everything
works fine. When I lower it, at about a 20 degree angle all hell breaks
loose. The floppies no longer work, and the system drops into ODT. At
first I thought it was the ribbon cable but that looks fine. Then I
thought it was the sockets having poor solder connections so I reflowed
them on the CPU board and the disk board. Still no. At this point I'm
thinking it is noise from the CPU board affecting the disk controller board.
There is a short of shield made of a layer of plastic paper, then a
layer of foil, then another layer of plastic paper that goes between the
boards. However it's not grounded, and I think that's part of the
problem. Any idea why there would be so much noise, and how to reduce
it? All of the ground wires are installed and there are a lot of them in
this thing.
C
