A 128 x 16 display runs far brighter than normal.

Small display much too bright (wrong D10 on a -00 supply)

Cause: D10 on the -00 supply has been swapped for a 1N4004, often on imported games to squeeze more life from a worn display. This lets far too much voltage through and wears the display out fast.

Checks

• Read the part number at D10.

Fix

• Fit the correct 1N5379 110 V zener. A 1N4764 (100 V) or 1N4763 (91 V) also works, with a slightly dimmer display.

The display power supply carries about 100 V or more; work on it with the game unplugged and let the capacitors discharge.

Systems

• Data East CPU Version 3

Games

• Batman
• Checkpoint
• Star Trek
• Teenage Mutant Ninja Turtles

Related tips

• Small 128 x 16 display looks garbled
• Small 128 x 16 display connector J2 pinout
• Small display shows vertical lines
• Test a loose 128 x 16 display glass
• Replacing R95 on the small display board without lifting traces
• DMD shows lines or garbage and no controlled lamps light
• Which DMD brands are hit by a blown lamp fuse
• Dot matrix shows lines or lights solid, and no CPU lamps work

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