5 Apr
2010
5 Apr
'10
4:28 p.m.
Speaking of early Commodore PETs, I have here a 4032 on which some of the keys
do not work. Some time ago I took a brief look at it and, as I recall,
concluded the problem was not the keyboard but rather something was messed up
with the scanning, something like not all columns/rows being scanned. I think
it was a 6821 or 6822 or some such doing the I/O, but the diagnosis was perhaps
more suggestive of something like a PROM bit failure causing the firmware
program to foreshorten the scan sequence.
Anyone have knowledge of a known failure mode of this sort with these machines?