The game plays normally, but as soon as the service menu is entered the outhole kicker (solenoid 1A) energises and stays on, heating up, and the 2.5 A fuse F2A on the auxiliary power board blows if it is left there. New driver transistors and resistors did not help.

Outhole kicker locks on whenever the service menu is entered: bad 7408 at U20

Cause: A failed 7408 logic chip at U20 on the CPU board was holding the solenoid drive signal on.

Checks

• Remove the solenoid fuse while troubleshooting so the coil can't cook.
• With a logic probe, follow the solenoid's drive signal back from the driver transistor through the TTL chips to the PIA and look for a line stuck high or low.

Fix

• Replace the 7408 at U20 (fit a socket).

Games

• Jokerz!

Related tips

• Kicker coil locks on again after a new TIP122: dead 7408 gate on the driver board
• Damage after the black and white plugs were swapped
• Which logic chips drive which solenoid transistor pairs
• Coil fires when tested but not in game play: TTL driver chip
• A coil or flasher comes on and stays on at power-up
• Background sound never stops at game over: sound-line driver chip
• How a coil or flasher is switched: PIA to TTL to pre-driver to driver
• Lamp column still dead after a new TIP42

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