A flipper's driver transistor (Q15) fails and blows the flipper fuse; a new transistor works for a couple of games, then fails again.

Flipper driver transistor Q15 and its fuse keep blowing: replace diode, adjust EOS

Cause: On this game the flipper coil has no diode on the coil itself: the back-EMF diode is on the driver board next to the transistor. A weak diode or a poorly adjusted EOS switch lets the transistor fail again.

Checks

• Measure both flipper coils (about 4.5 ohms here) and check that the plunger moves freely and the coil is not swollen.
• Test the protection diode beside Q15 on the driver board.
• Check the flipper EOS switch adjustment and the fuse clips at the flippers for looseness.

Fix

• Replace the transistor (the manual lists STP22NE10L), the protection diode beside it and the fuse together, and adjust the EOS switch.

Systems

• Stern S.A.M.

Games

• Metallica (LE)
• Metallica (Premium)

Related tips

• Upper right flipper locks up and blows its fuse after a loose coil wire: shorted MOSFET

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