The mandatory System 1 ground modifications
Steps
- With the driver board out, test all its transistors first and replace any bad ones.
- Power supply: solder an 8 inch wire to the negative (right-hand) lead of C1 and screw the other end to the metal backbox panel. Skip this on an aftermarket replacement supply that already grounds to its mounting frame.
- CPU board: solder an 8 inch wire to the negative (lower) lead of C16, the upper-left blue electrolytic, and screw it to the backbox frame.
- On a Ni-Wumpf CPU, scrape the mask off the wide ground trace under capacitor C0 and solder the wire there instead.
- Driver board: solder an 8 inch wire to the negative (bottom) lead of C1 on the right side and screw it to the backbox ground plane.
Systems
Related tips
- System 1 power supply outputs
- Acceptable System 1 supply readings
- Spare diodes, capacitors and other parts for System 1
- Quick checks on the similar System 1 power supply
- System 1 power supply shows about 110 V where 4 V and 8 V belong: wrong ground
- The 5/12 V supply is only half-wave rectified
- Getting to the power supply solder side
- All coils and most CPU lamps lock on at power-up
Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)