Does it blow F4 as soon as you turn the machine on or just when you try to use the flipper? Does it only blow with one flipper or either flipper? Which flipper? You could always try, just for giggles, disconnecting the wiring from the coils to see if it blows while disconnecting. If you do this put dome electrical tape on those now dangling wire while you have them disconnected so they don't short out with one another. Chime in here guys. Would this help isolate the problem to being on the board or within the coils?