'82 Bally drop target switch problem

dasvis

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'82 Mr & Mrs pacman. Fixed the display problem with help from the guru's in this forum, so here is another issue...

Running the self diagnostic test for the switches, it comes up with a the #1 switch stuck. This is the left bottom drop target in the bank of four. It has no capacitor to fail ---As per Clay's guide I have cleaned the contacts with a business card, & tested the diode (it was good). I see no broken wires. Still shows up as a stuck switch...
Any ideas?

Thanks in advance.... Mike
 
Make sure all of the wiring to the bank of switches on the drop target bank are good and all of the diodes are good...

It also could be a bad connector. This era of Bally games really needs to have ALL of the connectors rebuilt if you want it to be reliable.
 
Make sure all of the wiring to the bank of switches on the drop target bank are good and all of the diodes are good...

It also could be a bad connector. This era of Bally games really needs to have ALL of the connectors rebuilt if you want it to be reliable.

OK, so I need to test ALL of the diodes on that bank? I was wondering about that..
EDIT - Tested each diode, all are good.

Yes, I have a complete connector kit for the MPU sitting on my work bench. ---But I guess it does me no good unless it is installed!
 
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Bally pins of that era are notorius for bad connections. If you have time replace all the pins and connectors. That will probably correct the issue and chances are that it will stop some future problems. If you don't have time for a complete replace, trace the wires from that bank of switches in those drops back to their plugs and remove the pins from the plug and replace each of those. Bad or corroded pins cause early bally ss machines to do odd random things. The parts are cheap but teadious work to replace. I like to pull the pin from the plug and cut off the old pin. Strip the insulation, apply solder to the wire, crimp on the new pin and heat the pin to flow the solder and reinsert into the plug. give it a try and you will find that your bally machine will be a lot more dependable.
 
Bally pins of that era are notorius for bad connections. If you have time replace all the pins and connectors. That will probably correct the issue and chances are that it will stop some future problems. If you don't have time for a complete replace, trace the wires from that bank of switches in those drops back to their plugs and remove the pins from the plug and replace each of those. Bad or corroded pins cause early bally ss machines to do odd random things. The parts are cheap but teadious work to replace. I like to pull the pin from the plug and cut off the old pin. Strip the insulation, apply solder to the wire, crimp on the new pin and heat the pin to flow the solder and reinsert into the plug. give it a try and you will find that your bally machine will be a lot more dependable.

I plan on it! I like your idea of pre-soldering the wire end & reheating. Just a crimp always make me wonder if it was going to maintain good contact.
Is it best to remove the top door to get a good angle on the two left MPU connectors? If it were just a couple of wires to change out it would not be a problem, but there are a few more than that. The original connectors are the kind that the wire presses into across the top- I bought a Molex replacement kit for this, both the male & female sides of all four. looks like it will be a much more robust plug setup.
 
You can do it with the door on, but it's going to be a pain either way you look at it, lol. Lots of stretching and bending over the machine for about an hour or an hour and a half. When you get done though the thing will work perfectly.
 
FIXED!
The U10 socket was bad, found more green scum. Replaced socket & chip. IT WORKS!
- now just need to fix a few lamp issues, adjust some switches, rebuild the flippers & pop bumpers, re-sleeve all of the solenoids & clean'um up, clean playfield, add a free play button, re-rubber, replace the power cord, get new playfield glass (someone had replaced it with non-tempered), clean the cabinet ---- & then start looking for my next project.
Working on these is more fun than actually playing them!
 
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