How the pre-Xenon power supply works
Line power enters rectifier J2 pins 6 and 7, passes F6 (3 A slow) and feeds the transformer. Each secondary has its own fuse. Bridges turn 7.8, 12 and 49 V AC into +5.4, +11.9 and +43 V DC; the GI 7.3 V stays AC; four 1N4004 diodes (CR1-CR4) turn about 173 V AC into 230 V DC for the displays.
Line voltage (120 V AC) is present on the rectifier board and its J2 connector; unplug the game before touching it.
Systems
Related tips
- Checking the pre-Xenon supply with the game unplugged from it
- Replacement pre-Xenon rectifier boards exist
- Xenon and later: -54 power supply in the cabinet
- An upgraded -18 supply can replace a -49 in a pinch
- Safe first power-up of an unknown game
- Route of the +12 V supply to the MPU and 5 V regulator
- Make sure the power cord has its ground prong
- Differences between the -54 and -132 power modules
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)