Displays flicker in attract mode, flippers cut out or the flipper relay chatters, even after the usual power fixes.
Flickering displays and flipper drop-outs from a poor backbox ground
Cause: Later Bally backboxes ground the boards through foil-covered cardboard, which can lose contact; the solder mask on the MPU can also stop the board touching its brackets. A disconnected backbox earth cable has a similar effect (a dead player 1 display was traced to it on an Elektra).
Checks
- Check continuity from each board's mounting bracket to ground, and that the backbox earth ground cable is connected.
Fix
- Run a ground wire from one mounting bracket of each board to a true ground, scrape solder mask where the brackets touch, and connect the earth cable.
Systems
Related tips
- Rectifier board J3 (to backbox boards) pins
- MPU gives 3 flashes after reassembly: two 15-pin plugs swapped
- Three flashes and 8s or 9s in the hundreds digit
- Drop targets score but no longer light features: cracked switch matrix connector
- 12 V at the rectifier board but not at the MPU
- Knocker fires instead of the outhole kicker: bad solenoid driver J4 connector
- Four flashes only: U11 PIA, R134 or a bad display
- Flickering score displays
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)