Both 20-digit displays are blank, the display fuse on A12 has blown, the game acts oddly and may reset in play, and U9 on the display board runs hot.

Both alphanumeric displays blank and F5 blown

Cause: The latched fluorescent driver at U9 (TI5812N, UCN5812F or A6812) has developed an internal short from its Vbb pin (1) to its ground pin (14). It still draws from the +5 V side, dragging the unregulated logic supply down and resetting the CPU when coils fire.

Checks

• Feel U9 for heat.
• Measure pin 1 to pin 14 resistance with power off.

Fix

• Replace U9 (the part is obsolete and scarce).

Systems

• Gottlieb System 3

Games

• Amazon Hunt III
• Cactus Jack's
• Car Hop
• Class of 1812
• Deadly Weapon
• Hoops
• Lights...Camera...Action!
• Operation: Thunder
• Silver Slugger
• Surf 'n Safari
• Title Fight
• Vegas

Related tips

• Alphanumeric games use long-lived Futaba displays
• System 3 games with alphanumeric displays
• Never hot-plug the A8 board or the display

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)