Certain CPU-controlled lamps stopped working, often after the game was moved with the backbox folded down.

Some feature lamps out after the backbox was lowered

Cause: The lamp wiring to J10-J13 is short and badly routed, so folding the backbox pulls wires out of the IDC .100" connectors, cracks the header solder, or breaks wires inside their insulation.

Checks

• Look for cracked or cold joints at J10-J13 on the left side of the CPU board.
• Check for wires pulled out of the .100" IDC connector or the square .093" in-line connectors.
• Check continuity from the dead lamp socket to its J10-J13 pin, since a broken wire can look intact.

Fix

• Reflow the headers, repin the connectors and replace broken wires; give the loom more slack.

Systems

• Bally 6803

Related tips

• How the CPU keeps lamp phases in step
• Lamp driver SCRs on the CPU board
• Lamp driver SCR blew apart with a crack
• How 6803 feature lamps share SCR drivers
• Expected LED-strip results on lamp headers J10-J13
• An LED stays dark on a lamp header during the test
• None of the CPU-controlled lamps light
• Flipper switch shorting into the lane change switch

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