Two LM339s on the Fliptronics board read the flipper optos

Weak flippers are usually mechanical or coil faults, then aging cabinet optos that flicker unnoticed. After those, the two LM339 comparators on the Fliptronics board that read the optos can fail, though rarely.

Systems

• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)

Related tips

• Weak or dead flippers from failing LM339s on the Fliptronics board
• Fliptronics and WPC-95: weak flipper
• Fliptronics: flipper coil gets hot after a while of play
• Flipper gets weaker the longer the game is on
• Checking an under-playfield opto board for bad LM339s
• Opto switches dead all at once
• Confused switch matrix from LM339s on opto boards
• Opto ball troughs from Indiana Jones on

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