Ms. Pacman will not move up

Robot Ron 2

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I recently acquired an almost working Ms. Pacman. After fixing the monitor, I have discovered a second problem. "Up" on the joystick does not work.

I have checked all of the obvious. There is a solid solder connection with the white/red wire and the ground wire on the leaf switch. When I jump the two together, there is still no up movement. I tried jumping to a different ground point. I have also tested the white/red wire from the switch all the way back to the harness. I am hoping there is a simple solution because I am lost when it comes to troubleshooting PCB's.

Thanks in advance for any and all help.
 
Do you have connectivity onto the board itself? It may just be a dirty edge connector. It also may be a fault on the board itself, most likely with the pull-up resistor on that one line, or the 1st logic chip in the path.

Start simple tho, check continuity onto the board itself, if you have that then its a board fault. If you don't have continuity then it sounds like it dies at the connector for some reason which should be easy to cure.
 
Verify your wiring/joystick switch by using a meter set to continuity and test from the edge connector to ground on the pcb. If that checks out the problem is likely a bad (broken) resistor pack or a bad buffer (LS367) on the pcb.
 
If you need access to a working board, I am pretty local to you. I should have a spare working pacman plus board.. Plus I have a working ms pac cabinet.
 
You expect her to move up?

She's been hanging out with the same crew for 30 years. Same four walls. Sure, the scene changes from time to time, but even that gets old.
 
I looked at the schematics. It looks like "up" is "N" on the wire harness. It then goes to RM8 (blue component with 8 pins in a row)
R46
C21 then to
8E which is a 74LS367 chip

Physically, these components are ok, however, I know this means nothing.

So, my question is, should I replace each one of these one by one and test each time?

Thanks!
 
I looked at the schematics. It looks like "up" is "N" on the wire harness. It then goes to RM8 (blue component with 8 pins in a row)
R46
C21 then to
8E which is a 74LS367 chip

Physically, these components are ok, however, I know this means nothing.

So, my question is, should I replace each one of these one by one and test each time?

Thanks!

You can test RM8 and R46 easily with a multimeter. If those are okay, I would then go ahead and replace the 74LS367 at 8E.
 
Like mentioned you can ohm out the resistor pack to test it. Typically they dont fail other than physical damage but I have seen some that were cracked and it wasnt visible until I started to desolder it.
If you have a logic probe you can check the circuit. Just work your way in from the edge connector and look for a state change when the joystick is moved up. It should be high and go low when the switch is closed.
There is a row of .1uf caps and I have seen those go bad on many occasions which will cause the input to not work or be stuck on. I have seen the buffer ic go bad but more times than not its one of those caps.
 
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