F10 is for flashers and low powered solenoids. None of the solenoids should activate on power up, so it may be a bad flasher or blown bridge rectifier. Or a shorted transistor for one of the coils.
Put in a new fuse, and Pull Connectors J6 and J7 off the power board.
Power up....If the fuse blows again, possibly bad bridge rectifier.
If the fuse holds, plug in J6 and J7 one at a time, and see which one blows the fuse. Pay attention when you plug J6 in, to see if any flash lamps burn bright before the fuse blows. Or J7, if you hear any coil activate.