Have you checked the coils on the match and credit units?

Most bad coils on em games are easy to visually spot. Usually, the wrapper will at least be brown or blackened. Do any look bad? Maybe you could unplug the playfield and try to reset the game. If it still blows the fuse, you'll know it's
not something on the playfield.

My suggestion was to remove the jones pluggs going from the playfield to the bottom mech board. Once
these are repmoved, hit the reset button and see if the game starts the reset process...do the reels, players and ball count reset or does the game blow the fuse? The suggestion is meant to narrow down the short to on or off the playfield.