Pinball Drop Target LM339 RepairIR LED and sensor. A plastic "fin" on the drop target itself passes through here. Replacement LM339 chip. Switch matrix connections Power and ground Solder remover 
 The results of my job repairing the LM339 quad comparator. (I blew this IC while, er, unscrewing a nearby bulb while the game was on.) I soldered in a 14-pin socket in case something similar happens again, and I think it came out well. There is a minor problem - the drop target itself hits the raised chip when it comes down now, so it stays up about 5mm. Oops. Otherwise the drop targets are working perfectly now.
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What you're seeing here is the circuit board for a Williams pinball machine drop target (the things the pinball hits that drop down). This one has three targets, and three optical (IR) sensors that detect when the target is down. When the target is up, a piece of plastic is blocking the light in the sensor; when down the LED can be seen by the sensor. Inset is the flip side. I'm told the shiny stuff is flux, which can be removed with flux remover, of all things. CommentsWould you like to comment?Sign up for a free account, or sign in (if you're already a member). |
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FuzzyPhotos says:
Thanks for posting this photo. It was helpful to see how Williams used optical sensors. I had no idea they were built this way. I had a bank of drop targets on a BK2K where one of the targets, when hit, wasn't registering. I was able to separate the board from the targets (remove c-clips, etc.), clean the sensors, and then re-assemble, and all was well. I think new high scores may be coming with this fixed up.
Posted 9 months ago. ( permalink )