Finished a PF swap in a Xenon and now the F4 (solenoid) fuse blows during a game. It's running an Alltek MPU and SDB. During a solenoid test the Alltek SDB shows a short in the #14 solenoid, #3 drop target. It has a solenoid on each of the 4 targets plus a reset solenoid. During the test all 4 targets are dropped in order. I've ohm tested each of the 4 and the are within .001 of each other. The game was fully working, including the drop targets when I pulled the assembly and installed it in the new PF. The J2 connectors were re-pinned as well on the SDB. This game has 4 rollover buttons in the arch area that will drop each target in order. Initially only #1 & 2 were lit and functional. I did find a broken diode leg on the #3 switch caused by screwing the wiring loom hold downs in place. I re-soldered it. Now all the buttons will drop their target. The fuse blows during normal game play, nothing ever involving the drop targets. I've manually dropped and re-set the targets a dozen times without the fuse blowing. I have yet to even finish a game without the fuse blowing. Anyone have an idea?

Checked all that, didn't see an issue. Decided to isolate problem by activating solenoids manually. Problem is the left flipper. After activating & holding 20-25 times fuse blew. That flipper is not part of the yellow wire bus. I moved the switch and coil from the old playfield and only had to solder the coil lugs. I used the wiring from a donor PF and used my original as a solder guide.

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Good eye, that was the problem. I replaced it Saturday and so far so good.