I've bought a 6128 of unknown provinence from eBay. It had some dead RAM which I replaced and it booted up. Had a few hours of playing with it.
Decided to play some games this afternoon, plugged in a competition Pro joystick and noticed that some of the keys had stopped working, those associated with bit 7. I cleaned the end of the ribbons and the connectors, no luck.
I noticed though that with the keyboard disconnected I get a phantom "." keypress, sometimes a 0 too. I don't get this if I quickly power cycle if whilst warm, only when it's been off for a minute or so.
Any ideas what's going on? I'd suspected the membrane until I got these phantom keypresses. Faulty AY?
Did they joystick work with a CPC before?
It could still just be a membrane problem. First test I'd do is check if the joystick works correctly when the keyboard isn't connected. If it does, then your AY is fine and you just need to give the membrane a clean.
Bryce.