Quoted from tatman9999:I have the original manual in English and German . When I got the game one gate coil was missing. I replaced the coil with a new one that came with the game. I worked about 10 games and then the other coil went out. Few times the fuse under playfield blew. I believe the coil was missing because the guy I bought it from was having same problem and just did not install it. It works fine with one gate hooked up. It as soon as you hook both up is when it has the problem. I would think both gate coils at the same time is drawing to much power.
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I am looking at your pics and your drawing.
In the pic it looks like both of those small coils are wired to an Orange/black wire. I do not know if wiring two coils up in series is something that can be done without causing problems. But you say each coil, by itself, works and you only have problems when both are wired up.
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In drawing, it looks like there is only one solenoid coil wired to an O/B wire. Since by now, everyone seems to know that Stern's drawings have some problems, I don't totally know what to look for.
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I don't know this pin. I don't know the drawing. Are these coils activated by switches? i assume that there are. Can you figure out what switch or what switches activate the coils?
Do you see any coil wires from the SDU that are going to nowhere?
I am going to suggest you physically trace and touch every col wire and match them to the drawing. If you have a printer/ copy machine, make some copies so you can mark them up.