Check the RAM power-down protection

Steps

• Probe Z1 pin 9 and switch the game off: it should give a low-going pulse, which locks the settings RAM as power falls.
• Check the read/write line at Z5 pin 20: it sits high and goes low only when the CPU writes to RAM or the I/O ports.
• Right after power is applied, check the RAM enable at Z5 pin 17.
• Switch off and watch Z1 pins 9 and 11 for the power-down memory protect pulse.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• Control board A1-J1 power connector
• Game check-out, part 2: what a healthy power-up looks like
• Game does not power up properly
• The battery-backed 5101 RAM uses only data lines DB0 to DB3
• What each System 80 board does
• Game check-out, part 3: walk through bookkeeping and self-test
• Game check-out, part 4: coin chutes and meters
• Scores light at once and the status display stays dark

Source: System 80 Service Manual, Gottlieb