Twin Famicom - only the A button works

[ramsg8]

Hi, recently on my twin famicom only the A button would work on the controller, which I thought was an issue with the built in controller. To get around this I thought I'd get an adapter for the extension port to plug in an NES controller. The same thing still happens where only the A button works. Any help would be appreciated.

[fredJ]

I actually had a twin famicom with a problem I think was almost the same. We had to solder a wire underneath the motherboard. there some some contact going to the CPU that was corroded.

[Volo]

Let me try to diagnose the issue. Obviously the problem is with the CLOCK signal for the gamepad shift register.

If only PLAYER 1 gamepads are faulty - check the red traces on the schematics. If BOTH PLAYERS are faulty - the issue is with the blue connection.