Replace the System 80 reset circuit with a DS1811 chip

Steps

• Remove Z1, Q1-Q4, CR33, CR35, VR1, R8, R9, R43-R50, C2, C25 and C36.
• Jumper Z1 pin 5 to pin 9, and pin 11 to pin 13 without touching pin 12.
• Fit a wire link in place of R45 (this brings +5 V), and link the two upper holes of Q3 (emitter and base) to bring ground.
• Fit a DS1811-10 (TO-92) in the upper pads: pin 1 at R50 (reset), pin 2 at R44 (+5 V), pin 3 at R49 (ground), flat face toward the DIP switches.
• Keep CR34, R7 and C3. R10 and C14 can stay or go.

Systems

• Gottlieb System 80
• Gottlieb System 80A
• Gottlieb System 80B

Related tips

• DS1811 reset chip: which version to use
• Replacing the MPU reset section with a DS1811
• What the System 80 reset (watchdog) board does
• Reset section zener VR1 burnt on a System 80 CPU board
• MC34064 watchdog at CPU U10: pinout and substitute
• Why a System 80 CPU stops running
• Game won't boot, or keeps rebooting, because of the reset board
• Dead CPU board: check the reset line first

Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)