[vcf-midatlantic] FS: Processor Tech VDM-1 Video Board Tested/Working
systems.glitch at gmail.com
Sun Oct 8 14:48:11 EDT 2017
This board had some trace damage in the address jumper area, which was
repaired by installing machine pin sockets in all of the address jumper
positions. One position had the through-hole completely pulled out, with no
pads on either side -- the trace to this pin was repaired, and the pin
secured in place with two-part epoxy.
After repair to the address jumper area, it was found that the DM8131
address decoder was bad, this was replaced with a NOS part.
As shown in the listing, this board is now 100% functional and tests out
according to the Processor Tech manual. It was tested in my IMSAI 8080 with
an Intel 8080 CPU board.
Do note that this is an older design and requires I/O addresses to be
mirrored (high byte should be the same as low byte). This is standard for
8080/8085 CPU boards, but other CPU boards (e.g. Z80) may not support it,
or may require a jumper change.
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