AC and DC coils are different, and not just because of the back-EMF diode. For a given application, a DC coil will have more windings of smaller diameter magnet wire, and will have a higher resistance, than its AC counterpart. That's because, at the same voltage, you get a stronger magnetic force from DC than from AC.

When you take a coil originally designed to be a strong-kicking coil on AC, and drive that same coil with DC, the power of the coil will be much greater. So when converting coils in an old EM game to DC, it's good to keep this in mind if there are plastic parts that will get broken when the ball hits them with the extra force.

- TimMe

OK, so there were no changes to the stuff on the PF. But they did put different coils on the SS versions of those early games, right? That was exactly my point.

- TimMe

Fair enough. There did seem to be some trial-and-error going on during the industry transition to SS. I was repairing games out on location while that was happening in the late 1970s, and I can attest that it didn't always go smoothly.

- TimMe