I recently opened up a TAP to steal a port out of it, only to find the port wasn't even soldered in. Heh. Anyway, even if the port was soldered in - the input pins were dirty/poor contact inside (was checking what wires went to what pins with a controller cord and a logic probe). I don't think there's anyway to really clean these, other than bending the pins on the controller plug so they have more 'angle' to them and scrape/put more pressure on the connector inside. Else, just replace the DIN itself (if you can find them). The only other thing I saw in there, was a massive NEC 65005 series gate array. They custom by order, so good luck find a the massive chip replacement - if that's the problem.