(Disclaimer: if you plan on doing this repair, make sure to unplug your machine first--120 VAC can be dangerous.)
Ok, so this repair is not as exciting as the title appears. When I recently put my Centipede back together, I noticed that certain parts had been stripped, particularly the coin door area. Atari liked to put interlocks on the coin doors of its older machines, for safety reasons. Open the coin door, the power to the whole machine goes off. (That way the guy collecting coins has little chance of getting shocked.) My interlock had been stripped out, likely used as a repair part on another machine. You can see where the wires were twisted/black taped together. This is a sloppy and possibly unsafe scenario:
I took them out, separated the wires, and attached some quick disconnects:
Here's the interlock. If the plunger is pressed in (i.e. when the door closes on it) it makes a connection. If it is manually pulled out (i.e. during servicing) it also makes a connection.
Here is the interlock attached to the quick disconnects:
You can see in that picture that the AC wires leading to the interlock are fed through a rectangular mount. This is where the interlock snaps into place:
That's it. It's a small repair, but with these machines, every little bit counts.