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Midway MK2 PCB Player 1 Up Stuck On

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  • Midway MK2 PCB Player 1 Up Stuck On

    Fault:

    Player 1 up would be stuck on causing player to just keep jumping up.

    Repairs: Bad UG3 (74HC541)

    Traced the Up connection from edge connector to a 470 ohm resistor, 100pf cap, and a 4.7 resistor block.

    Check these parts for any shorts or any that maybe having a direct short to ground due to Pin 9 of UG3 (74HC541) being held low.

    I took out the resistor block that runs into the input side of a HC541 to disable any inputs from the player 1 side of the edge connector to see if all input side of the IC should be floating. I found that all inputs were floating but pin 9 was still stuck low.

    Replaced the IC and up is working correctly now. Its quite hard playing this game when the guy is jumping all over the place.

  • #2
    Well done! Certainly a game worth rescuing.

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