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Quoted from crazi:3) Checked inputs/outputs at 7402 at 1F (Nor gates from the test switches on the door). Inputs are all high and outputs low as expected. Pin 8&9 High and Pin10 Low.... Pin 5&6 High and Pin4 Low (all correct)
Next component up is a PIA.... any corrosion around any of these traces?
No, the outputs of the chips you measured go directly to a PIA's. Since you have the correct information coming in/out of the 7402s, the next component in the chain is a PIA. Those 7402's aren't connected directly the microprocessor.
If I read the schematics correctly the outputs of those 7402 go into *inputs* of the PIA. The displays working don't factor into that - different port. It's just the next item up.
If you have chips verifying as good I doubt it's going to be the eprom although that is not unprecedented - I had a sound eprom on pinbot that verified all day on 2 different brands of burners and it was still bad.
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