Why coils stay off until the CPU boots

The ASIC holds a blanking signal active from power-on until the processor has reset all the output latches, so coils and motors cannot fire while booting. Once ready, blanking goes to +5 V. A game that never releases blanking will have dead coils and lamps.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Dead CPU: no clock signal at the 6809
• What is on the WPC CPU board
• Dead CPU: check the reset and IRQ lines
• Which System 11 CPU boards fit which games
• The CPU must be a 68B09E
• What fails on a WPC CPU board
• CPU board from an early game won't boot: ROM jumper W1
• Dead CPU: isolate it from the other boards

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)