[vcf-midatlantic] Ti-99/4a Motherboard Troubleshooting

Bart Hirst louisbhirst at gmail.com
Sat Jan 1 02:49:58 UTC 2022

Hello, do we have any members that can assist with Ti-99/4a motherboard
troubleshooting?  I've already checked most of the "low-hanging fruit"
(voltages, clocks, overheated chips, traces, caps, troubleshooting steps
etc.) and i've been looking at pulseview output of various things with one
of those inexpensive 8-channel FPGA logic analyzers
you can pick up off amazon for $13.  This unit has the classic "black
screen and tone of death" going on.  So far I haven't been able to find
anything wrong except the 9900 seems to go into a ROM/RAM R/W loop.  Never
makes it to the GROMS.


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