After the start-up test the display asks you to check fuses F114 and F115, and switch test shows switch 24 (the always-closed switch) open. The fuses test good.

'Check F114 and F115' with switch 24 open: missing 12 V, bad bridge BR5

Cause: The unregulated 12 V supply is missing. Here one diode in bridge rectifier BR5 on the power driver board had gone open.

Checks

• Measure the unregulated 12 V at test point TP1 on the driver board.
• If it is missing with good fuses, check that AC is reaching the board (it was present at J112), then test bridge BR5 and its filter capacitor.

Fix

• Replace the failed bridge rectifier (BR5 here). The 12 V returned and the game played normally.

AC from the transformer is live on the driver board connectors while you measure; keep probes steady and power off before removing the board.

Systems

• WPC-Security (WPC-S)

Games

• Theatre of Magic

Related tips

• Shorted or open bridge rectifiers
• Driver board LED1 off (+12 V regulated missing)
• Live voltage checks for the F114/F115 message
• Pre-WPC-95 bridges, filter caps and fuses by supply
• Every opto dead and the opto board LED off: failed bridge BR5 for the unregulated 12 V
• Driver board LED1 off: switch matrix 12 V missing (WPC-S and earlier)
• No ball to the shooter lane and trap door or trunk dead: blown solenoid fuse
• Testing a bridge rectifier out of circuit

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