TP2 is missing, low, or will not adjust, and the score displays are dark or dim.

Score displays dead or dim: high-voltage section parts

Cause: Commonly failed parts: C6/C7, R5 (22k 1/2 W), C2 (160 mfd 250 V), Q1 (2N3584), Q2/Q3 (2N3440), VR1 (25k pot).

Checks

• With power off and drained, test D5-D8 (1N4004) and D10 (1N5275A) on diode setting: 0.4 to 0.6 V one way, nothing the other.
• Check R5 and VR1 resistance.

Fix

• Replace the failed parts, or rebuild the whole section.

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

• High-voltage input fuse FU2 blows
• Display high voltage above 190 V and VR1 cannot lower it
• Turn the display voltage down to 170 V
• +5 V still bad with good C1 and diodes
• Strange intermittent faults from power supply solder joints
• Power supply test points and their voltages
• Missing lamp fuse changes the flash count
• No +5 V at TP1 or no 14 V at TP5

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