Apple II no video display

Dave Wade dave.g4ugm at
Fri Oct 27 10:40:30 CDT 2017



I have an Apple II that produces one beep at power on, but my monitor says
"no video present". A scope on the output shows frame sync but at low
levels. The odd thing is that ic A9 appears to be a 74S151 not a 74LS151. I
wouldn't expect this to work, but I assume it was working at some point in


I have done some googling and can't see any reference to this substitution.
Is it something any one else has seen?


Dave Wade



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