Welcome to the joys of Stern's Whitestars. This happens on RBION, Monopoly and LotR, probably others, but those are the 3 I maintain.
It is not unusual to have the diode blow on these games. First thing to check is to make sure the diode is facing the right direction. I don't now if it was the wiring harness or a bad repair by a previous owner, but on my RBION the diode was going the wrong way.
3 ohms sounds a little bit low on the coils, I believe the specs on the coils are in the manual. You might want to check.