GI works but no feature (CPU-controlled) lamps come on.

None of the CPU-controlled lamps light

Cause: Blown lamp phase fuse FU4 or FU5, so a lamp phase is missing.

Checks

• Check FU4 and FU5 (8 A slow-blow).
• Measure TP6 and TP7 on the power supply for about 11 VAC each.

Fix

• Replace the blown fuse and find what shorted on that phase.

Unplug the game before pulling fuses or working on the power supply; the transformer side carries line voltage.

Systems

• Bally 6803

Related tips

• Some feature lamps out after the backbox was lowered
• Missing lamp fuse changes the flash count
• How the CPU keeps lamp phases in step
• Lamp driver SCRs on the CPU board
• CPU LED stops just short of the full count
• How 6803 feature lamps share SCR drivers
• Lamp driver SCR blew apart with a crack
• Where the boards sit in a 6803 backbox

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)