Its one of two things, the optos under the mini pf or the flipper optos. Thats the best place to start.
Clean all the optos under the mini play-field and the flippers. Could be a cold solder joint too, you may have to swap out the optos as they do fail sometimes. If that fails...
Marco has the motor/gearbox assembly for 58.00
http://www.marcospecialties.com/pinball-parts/14-7988
I would buy one anyway if I were you, I dont assume this parts will be around for ever. I have an extra in my parts drawer.
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