Midway gangbusters problem

playpin35

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I have a 74 midway gangbusters rifle game. When a game is started, the score reels reverse then advance to zero except for the 100s reel. It does not return to zero because the hit relay will stay energized and keeps the reel latch coil energized. When you start shooting the score reels continues to spin until the timer triggers the game over relay. You can manually switch targets through the program unit, so I know the mechanics work good. Pinrepair.com does not cover much on this type of game and most EM guys around here avoid them. Has anyone been around this type of game(being photocell/ part solid state) enough to offer any help or suggestions? I can't find anyone local to even take a look at it.
 
The light in the gun works and the recoil plunger in the gun works as well. It's almost as if the scoring board has the hit relay locked on and won't trigger the program motor to advance to the next target. I've even disconnected the target wires and the hit relay still stays energized. Any ideas? Anyone?
 
are you sure that there is no stray light hitting the photocell? sometimes the ambient light is enough to activate a hit. try turning down the sensitivity for the targets. if anything like twin pirate that'll be on the righthand board. -Al
 
What happened on mine(years ago)was screw on one of the finger boards loosened up and was getting caught up.It didnt allow full motion and was like locked on one set of contacts all the time.
 
are you sure that there is no stray light hitting the photocell? sometimes the ambient light is enough to activate a hit. try turning down the sensitivity for the targets. if anything like twin pirate that'll be on the righthand board. -Al

It still does it in complete darkness. I have also tried adjusting the sensitivity and it still no change.
 
Have you tried disconnecting the photocell(s) as these sometimes go faulty and register even in the dark. Sound like you are on the right track with the hit relay. If you disconnect this does this allow the scores to reset?

regards Derek
 
I removed both wires going to the photocells and the hit relay still stays energized. If I remove the blue-yellow wire(one of the hit relay wires)from the connector, the relay will release and the score reels will reset to zero. As soon as power is applied from the start relay, the hit relay energizes and only releases when the game over relay is energized.
 
If you have removed both the white-green and green-yellow wire which run to all the optos and the hit relay is still being triggered then the photocell board is probably faulty. Have you tried adjusting bost the sensitivity pots on the board. Is this doesn't help then the board may have a transistor which is shorted and locking on the coil.
 
I have replaced the 3 TIP 31C transistors and it still remains energized. Now looking at the schematics, it has 2 looping arrows that states 47K. I assume they are referring to the adjustment pots as I can not find any other resistors with these values. With my meter, I get from 0-7.8. Not sure if this means they are bad or not as I have never worked on one of these before.
 
There isn't a lot of parts on the board so you could replace the other transistors and diodes for a small cost. Does your meter have a diode test? You could check the A138 transistors and zener diode. To measure the pots, you will have to unsolder them first.

Were the original parts TIP31C? Just wondering as the schematic shows a different value.
 
Were the original parts TIP31C? Just wondering as the schematic shows a different value.

That's the number on the transistor housing and the board had no evidence of them ever being replaced. The game was unmolested and had sat for 20 years prior to me getting it, so that's what I replaced them with.
 
With the pots and diodes removed, the hit relay still stays energized. The only way to release the hit relay is to unplug the board. I'm at a loss as I'm out of things to try and not sure what to do next. I don't want to give up on it, but it is starting to piss me off.
 
I checked them with my meter and none of them appear to be shorted. I will have some time this weekend to spend on it, but not sure where to go from here and there are no EM guys locally that can help me out.
 
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