Fuse F7 (5 A, feeding the sling coils and flashers) blows immediately at power-up. The sling coils had already been replaced.

F7 blows at power-up: flasher socket tabs touching, which also shorted Q27

Cause: On the Chef VUK flasher socket, the ground lead had been bent over so it touched the other tab, shorting the flasher. That short had also killed its driver transistor, Q27.

Checks

• Check every flasher socket on the circuit that fuse protects for tabs or leads touching.
• Test the driver transistor for that flasher once the short is cleared.

Fix

• Separate and insulate the socket tabs (or replace the socket) and replace the shorted transistor.

Systems

• Sega/Stern Whitestar

Games

• South Park

Related tips

• One flipper flips but has a weak hold and drops when hit: bad transistor at Q16
• Resets when the flippers are used: arcing flipper coil, then bridge rectifier BR21
• Won't boot after a board swap, CPU LEDs dark: loose 5 V wire in the CPU power plug
• After cleaning the cabinet most coils are dead and the display goes dark: reseat J16
• Whitestar flipper weak or dead after a MOSFET swap: fake part, test with TPL1
• Whitestar: I/O board blanking LED flashes, lamp rows 1 and 3 dead: data bus short

Source: Pinball Repair help group!! (Facebook group)