Williams solid state pinballs with the piggyback driver board had
under-designed some of the resistors. The column of large resistors on the
right hand side of the board (R149-R156) often burn themselves up. They
have also been known to get so hot they desolder themselves. These were 2
watt 27 Ohm resistors. Replace them with 3 to 5 watt 27 Ohm ceramic
resistors. Be sure to mount the resistors at least 1/8" off the board so
the board doesn't get cooked.