Logic probe states in attract mode: U16 9602 and U15 MC3459
U16 (9602): pin 1 low, 2 low-pulse, 3 high, 4 pulse, 5 high, 6 and 7 pulse, 8 low; pin 16 high, 15 low, 14 low-pulse, 13 high, 12 pulse, 11 high, 10 pulse, 9 pulse. U15 (MC3459): pins 1-6 pulse, 7 low; 14 high, 8-13 pulse.
Systems
Related tips
- After work on U15 or U16, check the traces under them
- No clock at the CPU: U15, U16, C14/C15
- Six flashes only: 43 V, U10 or U14
- Seven flashes but no attract mode
- Garbled player 1 display and strange play from a bad 5101 RAM
- Tracing the VMA signal through U19, U14 and U15
- MPU board test point voltages
- MPU stops before the 7th LED flash (no 43 V)
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Two, Clay Harrell (pinrepair.com)