A 128 x 32 display stays dark or garbled although power and ROMs are good.

128 x 32 display dead: check the PALs at U2 and U16

Cause: One of the two custom PALs, U2 or U16, has been damaged by static. U16 fails more often.

Checks

• Verify the voltages and ROMs first.

Fix

• Replace U2 with a TIBPAL16R4-25 programmed to checksum 50D8, or U16 with a TIBPAL16L8-15 programmed to checksum 6489.

Systems

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

Related tips

• Small 128 x 16 display looks garbled
• Test a loose 128 x 16 display glass
• Small 128 x 16 display connector J2 pinout
• Medium 128 x 32 display connector P1 pinout
• Large 192 x 64 display power connectors by display maker
• Large display restarts when both flippers are held
• Build your own 192 x 64 display power harness
• Display dark at the edges until it warms up (outgassed glass)

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