Even with new EOS switches and flipper contacts, the flippers are just short of the power needed to make the shot to the top saucer.

Flippers too weak for the top lock: loose, arcing bridge rectifier connections

Cause: The spade connections on the flipper/solenoid bridge rectifier were loose and arcing, so the coils were not getting full voltage.

Checks

• Look at the rectifier's spade terminals for discolouration or looseness.
• Jumper across the EOS switch briefly to rule it out.
• On System 6 and 7 games the flipper base coil stop is not removable and wears; a later bracket with a replaceable stop adds snap.

Fix

• Replace the bridge rectifier and its connections (a fused replacement rectifier was used here).

The rectifier is fed from the transformer; switch off and unplug the game before working on it.

Systems

• Williams System 6 / 6A

Games

• Firepower

Related tips

• Right flipper too weak for the top lock after a rebuild: lighter return spring
• Loose wires on the backbox bridge rectifiers
• Firepower right flipper switches sit close to the pawl: a short kills the switch matrix
• All controlled lamps out: bad spade connections on the bridge rectifier
• Test a bridge rectifier with a meter
• Backbox bridge rectifiers and their wires
• The backbox bridges and can capacitor are not logic power

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