Booting a CPU board on the bench

Steps

• Connect a PC switching supply to the CPU board's A1P1: +5 V to pin 1, ground to pin 4.
• Power up and watch the LED: steady flashing means the board has booted.
• To go further, connect A8 by ribbon from A1P3 to A8P3 and power A8J1: pin 9 +5 V, pin 5 +20 V, pin 10 ground, pins 1-2 58 VAC, pins 3-4 95 VAC.
• Ribbon the display to A8P4 and wire A8J2 to the display: pin 1 to display pin 6 (+5), pins 2-3 to pins 4-5 (ground), 4 to 7 (+12), 5 to 8 (+62), 7 to 1 (-112), 8 to 2 (-100).
• The set should run attract mode animations, which helps diagnose the CPU board.

The display controller runs on 58 and 95 VAC and puts out over 100 V; insulate the bench wiring.

Systems

• Gottlieb System 3

Related tips

• CPU board LED never lights
• CPU board 26285 versus 26285-1
• Main chips on the CPU board
• CPU board connector uses
• Missing P6 or P7 header on the CPU board is normal
• CPU board EPROM and RAM size jumpers
• Logic chips worth stocking
• U11 must be a 74HC123AN

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)