Optional ground mod steps 2 to 9: driver board ground jumpers

Steps

• Component side: wire the via at J5 pin 3 to the via under Q59's leftmost leg.
• Solder side, J4 at the bottom, pins counted from the "1" mark: scrape the trace just above the pins that runs to J4 pin 15 (ground) and wire pins 9, 10, 11 and 14 (solenoid grounds) to it. Leave the lamp ground (J4 pin 5) off this solenoid ground.
• Link the two lamp grounds: wire J4 pin 5 to the via roughly 3/4" above J4 pin 6, which also goes to J3 pin C.
• Wire the emitter trace of Q43 (right pin) to the emitter trace of Q51 (bottom pin).
• Scrape the wide Y or T-shaped trace above the "J3" label that comes from J3 pin U, below Q23, and join Q23's lower pin (emitter) to it.
• Wire Q9's right pin (emitter) to the same trace, and run another wire from it to the traces of J3 pins 9 and 11.
• Join Q25's emitter (lowest pin) to the scraped trace just under it.
• Keep all these links in place if any of these transistors is ever replaced.

Systems

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

Related tips

• Ground mod step 5: direct ground wire to the driver board
• Use heavy wire for the optional driver board ground jumpers
• Test the driver transistors while the board is out for the ground mod
• Test driver board outputs by grounding transistor tabs
• First power-up, step 5: add the driver board, then coil power
• Diode-test a driver board 2N6043
• Diode-test a driver board 2N3055
• Coils lock on and burn because of the Gottlieb ground fault

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