Replace high-voltage caps C6 and C7 before they take out Q2/Q3

Caps C6 and C7 (.01 mfd 500 V) in the display supply often fail, and once they do, transistors Q2 and Q3 (2N3440 / NTE396) can burn out within about a minute of power. Replace the cheap caps as a precaution.

The display supply runs at 170-230 volts DC; touch nothing on the high-voltage section with the game on, and let it discharge before working on it.

Systems

• Bally 6803

Related tips

• Rebuild the high-voltage display supply
• High-voltage input fuse FU2 blows
• Turn the display voltage down to 170 V
• Display high voltage above 190 V and VR1 cannot lower it
• Power supply test points and their voltages
• Random resets and lock-ups from the +5 V filter cap
• Strange intermittent faults from power supply solder joints
• Where the boards sit in a 6803 backbox

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)