Strange Super Pac-Man PCB Problem

LyonsArcade

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Hi guys;
I've got a dedicated Super Pac-Man that I'm working on, and it has a strange issue. The character won't go left, or down. Right and up works great. If you switch the wiring around at the pcb, left and down on the joystick work if you hook them up to the up and right inputs, so I don't believe anything is wrong with the wiring or the joystick.

If you put the pcb into test mode, it says all roms, rams, and inputs are fine. Also, in test mode, all the directions work to change the 'sound' test. So it appears that there's actually nothing wrong with the 'input' of the board, only the 'output' of the video or whatever to make the character actually move to the left or down. It's like the game is getting the correct signal from the joystick, but just won't actually make the character move that direction.

When the inputs go in the board, they run through a set of resistors and then into one of those large Super Pac custom chips. There's another custom chip that handles the dipswitches that is the same number, I switched those two around and there's no change. I checked the sockets, and they check out fine. If you 'ohm' the resistance from the pin on the pcb through to the pin on the custom chip that it connects to, you get 2.2k which is the value of the resistor those lines run through; all the 8 direction inputs ohm out the same all the way to the custom chip (I checked player 2 even though it doesn't wire up in the upright). None of the directions are shorted to each other either.

Does anybody have any idea what I can check next? I'm pretty sure it isn't an input problem, but something after it goes through that custom chip. I've cleaned and reseated all the custom chips on the board.

Any help is appreciated!
 
Alright, I got a TESTED WORKING Super Pac pcb in... and dammit if I don't have the same problem. What the hell?

It's got to be in the cabinet now of course, but the crazy thing is if I measure continuity from the switch on the joystick, allllll the way to the pcb it ohms out fine! And if I measure all the grounds are connected together, and if I activate the joystick I get a ground signal all the way to the pcb. (if I put the meter on the pin and the ground, then use the joystick, it zeros out).

I'm thinking maybe a wire is stuck ON somewhere or something? In test, it works fine! In the game, it doesn't. Makes 0 sense!
 
Hmm, I would have said that the grounds in the cab are not common, its worth checking this when the board is disconnected from the cab.

Its also worth checking that the pins in the cabinet socket are totally lined up with the edge connector fingers on the edge connector. On many boards its possible to get things out of allignment and have the socket bridge two edge connector pads.

Beyond that I would suggest holy water.
 
All the grounds go common at the cp plug, and the game doesn't use edge connectors but does use inline molex? plugs at the board like a pinball board does.

I'm going to mess with it today, I'll post back when I find out what's going on. Like I said, it works in the test menu. Just doesn't in play, I've got to be missing something. I'm going to remove the wires one at a time and add them back until one doesn't work or something, it might be as easy as a button's stuck together and confusing the input 'matrix' or whatever.
 
Just thought I'd update incase anybody searches for something similar and finds this.

The clue was when the game starts, Pac-Man was heading to the right.

In a properly working game, he starts out heading to the left. The right wire was shorted to the ground in the control panel harness. I thought I checked the switches on the joystick, but I actually only checked to make sure that they were getting good continuity when they were pressed. I didn't notice that the right direction was always 'on'. This confused the board and it wouldn't let you go left or down because you were already going right. For some reason it would let you go up, but I guess that's just how it thinks.

Replaced the wire in the control panel and voila! everything works fine. Fun game too.
 
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