A game left on finds both slingshot coils and all pop bumper coils burned, with blown transistors and ICs in the special solenoid section of the driver board.

Slings and pops all burned at once: CPU lock-up from the 40-pin interconnect

Cause: The CPU locked up, leaving the special solenoids switched on. The usual trigger on these games is a poor connection in the 40-pin interconnect between the CPU and driver boards, which carries the bus to the PIAs. An oversized solenoid fuse let the coils cook instead of the fuse blowing.

Checks

• Check the solenoid fuse values against the manual and look for oversized or bypassed fuses.
• Inspect the 40-pin header and connector between the CPU and driver boards.
• Test the special solenoid section parts (7402 and 7408 logic chips, 2N4401 pre-drivers and TIP102 drivers).

Fix

• Replace the 40-pin interconnect with a good one (or rework the headers), repair the special solenoid circuits, fit new coils, and use correctly rated fuses. Don't leave the game on unattended until it's proven stable.

Systems

• Williams System 4

Games

• Flash

Related tips

• Solenoid fuse blows at power-on and solenoids fire: driver board logic chips
• Coils 1-8: connector, transistors, PIA pin
• A low resistance coil points to a bad driver transistor
• All coils or lamps lock on at power-up
• Coils 9-15 and coin lockout: connector, transistors, PIA pin
• Coil still locked on with good transistors and gate
• CPU locks up as soon as the driver board is connected
• Driver board transistors and what they drive

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