Hitting any of the tune (jukebox) targets registers several other switches. Diodes test fine and lifting switch capacitors changes nothing; the CPU board tests good.

One target triggers several switches: switch blade shorting to its mount

Cause: A switch blade was touching its metal mounting bracket, connecting the matrix to the frame.

Checks

• With power off, check continuity from each switch blade to its metal mount; there should be none.
• Look for diode leads touching metal and for solder splashes; the fault may be on a different row or column.

Fix

• Re-seat or insulate the blade so it can't touch the mount.

Systems

• Bally 6803

Games

• Party Animal

Related tips

• Hitting the jukebox targets triggers several switches: blade touching its mount
• Keypad keys are switch matrix crossings
• A missing keypad locks you out of the menus
• Build a replacement keypad
• Flipper switch shorting into the lane change switch

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