When entering high score initials the flipper buttons don't move through the letters, though start works as enter and the flippers play normally.

Funhouse: flipper buttons won't step through high score initials

Cause: Optocouplers U7 and U8 (4N25) on the power driver board have failed. On this non-Fliptronics game they only report the flipper buttons to the CPU; they were dropped from later driver boards.

Checks

• Test or swap U7 and U8.

Fix

• Replace U7 and U8 with 4N25 optocouplers.

Systems

• WPC Alpha-Numeric

Games

• Funhouse

Related tips

• Pre-Fliptronics: flipper lane change does not work
• Flipper buttons not seen by the game (pre-Fliptronics)
• Row or column "ground short" errors
• Lane change not working on Taxi and later System 11 games
• Upper right flipper only buzzes while the magnet holds the ball: failed opto-isolator
• Phantom switch closure that survives a new CPU board: bad 4N25 on the driver board
• WPC: phantom switch closures traced to a 4N25 on the -1 driver board
• Game keeps resetting during play: poor J101/J102 power connections

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)