All the switches on one or two switch board connectors stop working or work only now and then.

Groups of switches dead or intermittent: loose surface-mount LM339s

Cause: The surface-mount LM339 comparator chips on the switch matrix board lose their solder bond from vibration. The chips nearest the board edges go first, most often the two to four at the left end. The chips themselves are usually fine.

Checks

• With the game in switch test, press lightly on each LM339 with an insulated screwdriver; if the dead switches come back, that chip's pins are not making contact.
• Look at the chip pins under magnification for joints that are cracked or lifted from their pads.

Fix

• Reflow the pins of the affected LM339s (see the surface-mount reflow procedure).
• If reflowing does not cure it, replace the switch matrix board.

Systems

• Capcom

Related tips

• Reflowing surface-mount chips on the switch matrix board
• Weak or dead flippers from failing LM339s on the Fliptronics board
• Opto switches dead all at once
• Optos test good but still don't work: the opto board
• Confused switch matrix from LM339s on opto boards
• Gumball enter opto (switch 87) never registers: replace the LM339
• Switch matrix chips on the CPU board
• Checking an under-playfield opto board for bad LM339s

Source: Capcom Pinball Problems/Solutions