Random horizontal lines or garbage on the dot matrix (on 128x16 games it may then light fully), while the game plays but none of the CPU-controlled playfield lamps light.

Dot matrix shows lines or lights solid, and no CPU lamps work

Cause: The backbox 18 V lamp matrix fuse (8 A slow-blow, blue/white wire on its holder) has blown. On these games the +12 V for the display is made from the 18 V lamp supply through power supply CN5, not from the sound +12 V on CN6.

Checks

• Check the 18 V lamp fuse in the backbox.
• If it blows again at once, look for a lamp matrix short or a bad lamp bridge or capacitor.

Fix

• Replace the fuse with an 8 A slow-blow; repair any short or bad bridge first.

Systems

• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Games

• Adventures of Rocky and Bullwinkle and Friends
• Batman
• Checkpoint
• Guns N' Roses
• Hook
• Jurassic Park
• Last Action Hero
• Lethal Weapon 3
• Star Trek
• Star Wars
• Tales from the Crypt
• Teenage Mutant Ninja Turtles
• The Who's Tommy Pinball Wizard
• WWF Royal Rumble

Related tips

• DMD shows lines or garbage and no controlled lamps light
• DMD dark after work in the backbox: transformer wire pulled out of its plug
• Fit a 120 V plug, line fuse and MOV
• After a bulb change, coils dead and a flasher fires the knocker: blown supply fuse
• A 520-5047-02 supply can stand in for a 520-5047-01
• Adding jumper wires across DB1 and C4 (520-5047-00/-01/-02)
• DMD shows lines or lights up fully, and no CPU lamps work
• Small display shows vertical lines

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)