View Full Version : Midway MK2 PCB Player 1 Up Stuck On

31st January 2009, 05:17 PM

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.

2nd February 2009, 01:18 PM
Well done! Certainly a game worth rescuing.