I'm trying to repair a friend's Lynx II that is stuck on "insert game". I replaced U9 (74HC164) which was hot and seemed to be shorting out some pins, but still get the message on power-on.
Tracing the signals, I see repeated attempts at resetting the 4040 on MOTORON, but the chip selects from Suzy don't seem to move at all, so the clock input is stuck high. At first I thought a trace was bad, since I was seeing activity on the gate output on U7, but I suppose they changed the gate used on the package in this revision wrt the schematics I have…
Suzy seems to get all signals properly from the CPU, the clock is a bit ugly but it's there… Not sure what to check now. I replaced the two large caps on the power input, but maybe the other caps are getting weak and disturbing the chips?
Tracing the signals, I see repeated attempts at resetting the 4040 on MOTORON, but the chip selects from Suzy don't seem to move at all, so the clock input is stuck high. At first I thought a trace was bad, since I was seeing activity on the gate output on U7, but I suppose they changed the gate used on the package in this revision wrt the schematics I have…
Suzy seems to get all signals properly from the CPU, the clock is a bit ugly but it's there… Not sure what to check now. I replaced the two large caps on the power input, but maybe the other caps are getting weak and disturbing the chips?