Hi everyone, this ist my first post and i would like to introduce myself first.
Im 40 years old, married with 2 children from Northrine-Westfalia in Germany. I recently bought a house and we found a pinball machine in the cellar. Since my children would love to play this pinball (my wife also) and i really love repairing "old stuff" ,-) im trying to get it operational again.
Its a Fun-Fest pinball from 1972 by Williams . Im a mechanical engineer so im not useless with my hands, but electrical wise i need some step by step instructions. Soldering will work although it will take some time i guess

Ok but now to my problems: First of all the pinball machine works. I get most of the lights, the two flippers work, scoring seems to work (ok some rubberbands are just hair rubbers from my daughter at the moment) . But what preety much does not work at all are all the bumpers. The fuses seem to be ok. 3x15 Amp fuses and one 10A fuse seem to be working fine.
So since all the bumpers are not working i would assume that not only one coil is out of order or are they all connected by each other?(so one does not work, all are not working?) I found the schematic online and attached the part of the bumpers. So the red part preety much does not work alltogether, while the blue part (the flippers) seem to work. So i dont really know where to start looking. The bridge Rectifier (i honestly do not know where to find this thing) should be fine, since the flippers use it aswell? Is this assumption right?
Can someone give me some step by step instructions how to check if the coils are working? I have a Voltmeter so i can try to measure the resistance of the coil or something like that.
Another question: I do not have a key to open the scoring board (on the backside there is a metal plate with a keyhole). Is there a simple trick to do this with a screw driver?

Best regards
Sven

Bumpers (resized).JPG