neogeo 1 slot player one controls do not work

[gmtransman]

i have a neogeo one slot that all the buttons and joystick switches are stuck on the  player one. player two works fine. different board works fine in cabinet.  where should  i start. thanks

[channelmaniac]

Measure the resistance from the player 1 inputs to +5v. There's a resistor in a resistor pack in there that ties them to +5v so they sit at logic high until the button is pressed. I forget the value, but it'll be the same for Player 2 controls. If the resistor pack is broken, it will be floating instead of being logic high.

Check continuity and for trace damage.

Follow the traces back to the NEO-C1 chip (newer boards have a different chip...) to make sure you have no trace damage.

If everything checks out, replace the chip.