Recently purchased a barely functional 1976 Bally Old Chicago and I am working through the process of restoring it. The other night while testing it, the drop targets stopped resetting. Upon further inspection I found the link connecting the drop target solenoid plunger (4) to the reset arm (5) had worn through.
At some point in the machine's history, the shoulder stud had been replaced by a 2" long flat 1/4" screw and secured with 2 square nuts. There was lots of play in the screw and obviously over time the threads on the screw acted like a file and chewed their way through the end of the link.
I was able to order the shoulder stud (S-458-26) and link (P-1973-337) from Pinball Resource but until the parts arrive, the drop targets are out of commission.
Unable to accept this, I decided to try and repair the link. I took a piece of glass and wiped a very thin layer of light oil on it. I placed the link on the glass, put a few washers on the undamaged end to weight it down and overfilled the the hole on the damaged end with epoxy. I let it cure overnight then trimmed, shaved and sanded the excess epoxy into the shape of the original link. In fact I left a little extra at the bottom of the link to add some extra strength.
I exchanged the flat screw with a shorter 3/4" long 1/4" pan head screw and reused the two square nuts. Put it all back together and tested it.
After 20 games and approximately 100 drop target resets the repair seems to be holding. When I get the replacement parts, I plan to install the shoulder stud, but I think I will keep the repaired link in place to see how long it will last before it fails.
There are similar links in the flippers and other solenoids. Is there a source of the link material in larger "boards" that can be cut a shaped as needed? Has anyone considered making "boards" using fiberglass/kevlar/carbon fiber and resin to make a more durable link?