Posted Fri Sep 30, 2011 6:34 AM
Hmmm, if the A button is functioning as the Start/Pause button then there's the possibility that whatever it damaged is related to the IC on the controller's main board. If your Start/Pause button is still doing its job then it could just be that the rubber pads under the buttons are destroyed, but those can be found in replacement kits.
If you've never taken apart a nintendo controller before, what you'll find inside is a series of plastic buttons (the D-pad, A, B, Start and Select, obviously) and laying on top of these buttons are sections of rubber membranes (one for the D-pad, one for the A+B and one for the Start+Select) Each rubber membrane has a dome-like shape, kind of like a half bubble, which allows it to spring back into position after being depressed by the button. On the bottom of the dome is a little metal contact. When you press a button, the dome is depressed, the metal contact connects with the circuit board and completes a connection. It's a pretty simple setup.
The NES Max is no different, it just has a couple extra membrane to accomodate the turbo buttons. (Pretty sure the circle button is not really a button, it just resides inside the black ring, which looks like a regular D-pad from the bottom side)
Sometimes, the rubber membranes can tear and rip with use and then they no longer function correctly. These membranes can usually be bought as part of a refurbishment kit that you can find online, either on ebay or elsewhere. If the rubber membranes are intact, it could be that the metal contacts are just dirty, both on the dome undersides and on the circuit board. The circuit board contacts should be shiny, while the metal contacts on the dome undersides should be grayish-black. I've had success using an eraser to remove crud build-up.
Another option that I've had success with in repairing NES Advantages is to cut a tiny circular piece of tin-foil no larger than the metal contact on the underside of the dome. Super-glue the tin foil to the metal contact and it should restore functionality (provided the membrane is intact).
In any event, go ahead and take apart one of the new-used NES Max's you got. It should be painfully obvious is something is broken (so you shouldn't have to open up your working one). While in there, make sure to check the controller cord connections to the circuit board; sometimes those can break. If you have a multi-meter, use it to check for continuity between each pin on the controller jack and the circuit board. (it could be you're dealing with a bad cord!)