To make sure it's on your playfield - unplug the jones plugs from the playfield to the game, there are 2 of them (make sure the power is off).
Replace the 10A fuse (I'm sure it is 10A for lights on a Williams pin) and if the fuse doesn't blow with the playfield unplugged you know the short is on it.
You will need to take your time and really feel your pain...I still have this problem on my World Fair and have just given up for now!
