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UDN6118/UDN7180 pinout and what each failure looks like

Both chips have inputs on pins 1-8, outputs on pins 11-18, ground on pin 9 and -100 V on pin 10 (pins 1 and 18 often unused on the 7180). A failed 7180 affects one display on later two-display games or two displays on older five-display games; a failed 6118 usually kills half a display. If a display is totally dark with plus and minus 100 V present, the glass is the likely fault.

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Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell