F5 on the playfield power (PPB) board blows, and a fuse in the backbox blows the instant the game is switched on.

Data East/Sega: PPB fuse and backbox fuse blowing: shorted Q3 and a plug one pin over

Cause: Two separate faults: the TIP36C transistor at Q3 on the PPB board had shorted, and a previous owner had plugged a power supply connector (CN4) on one pin offset, shorting the supply.

Checks

• Meter the transistors on the PPB board; a shorted one reads near zero.
• With power off, measure resistance across the blowing fuse and unplug the load connectors one at a time until the short disappears.
• Check every power supply connector is on its header squarely and not shifted by a pin; look for burnt connectors while there.

Fix

• Replace the shorted Q3 transistor on the PPB board.
• Refit the offset connector correctly and replace any burnt connectors.

Fuse hunting involves the transformer and supply; take resistance readings with the game unplugged.

Systems

• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• PPB fuses on the nine-fuse board
• Dead or intermittent circuit from a cracked fuse clip
• MRB and PPB playfield power boards
• Under-playfield relay boards and the PPB board
• Only GI for 10-15 minutes after power-on, coils lock on and blow fuses: weak 5 V supply
• A coil or flasher comes on and stays on at power-up
• What the PPB/MRB board carries
• DMD shows random garbage after reassembly: failed display driver board

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