How 6803 flash lamps are multiplexed

A 43 VAC transformer winding is center-tapped into two 21.5 VAC phases, C and D, that feed the flash lamps directly with no rectifier or filter. Two flashers on different phases share one SCR on the CPU board, so each driver can run two flash lamps. Flashers never share a driver with a coil, because the coils run on DC.

Systems

• Bally 6803

Related tips

• Fire a coil by grounding its driver tab
• Expected LED-strip results on coil headers J6-J9
• How to read the flashes on pre-1988 6803 games
• How to read the flashes on the last four 6803 games
• Missing lamp fuse changes the flash count
• Electronic spares for 6803 board repair
• Cybernaut can have a -35, 6802 or 6803 boardset
• How the CPU keeps lamp phases in step

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