weird controller port issue

[funknflow5200]

so I got a 7800 the other day that was in pretty rough shape, had to swap out most of the switches to get it to work ( pause button is still faulty). the issue that remains is this: when playing 7800 games that require two buttons, the fire buttons on the joysticks do not work. games that require one button: fire buttons work fine. on atari 2600 games everything works great except my paddles will not register movement. has anyone had this issue? I'm at a loss. I reflowed all the solder on the controller port. maybe I just need a new motherboard? help!

[+DrVenkman]

I believe the TIA chip registers paddle movement as well as the triggers for joysticks. The 7800 (again, going from memory) can use two fire button on the joystick by using a combo of the paddle input signals for the second trigger. With the combination of problems you describe, that's where I'd start troubleshooting.

Edited October 24, 2015 by DrVenkman