After swapping the display, the dot matrix stays black. A known good DMD controller from another game (with this game's ROM) works, so the fault is on the original controller board (520-5055-01).

Black DMD: Data East DMD controller has no clock past the 74HCT240 at U1

Cause: The 74HCT240 buffer at U1 that passes the crystal oscillator clock on to the rest of the board had failed, so the board's CPU never ran properly.

Checks

• Check 5 V on the board and reflow the power connector joints, which often crack on these boards.
• Work through the usual order with a logic probe: power, clock, reset, ROM, RAM, bus activity.
• Follow the clock from oscillator X1 into U1: the input (pin 11) should pulse and so should the output (pin 9). Lift the output pin to see if something downstream is holding it.
• No pulse on the output with a pulsing input points to a dead U1.

Fix

• Replace the 74HCT240 at U1, preferably fitting a socket.

Systems

• Data East CPU Version 3

Games

• Last Action Hero

Related tips

• DMD stays dark while the game plays music: 74HCT240 on the display controller
• Dot matrix controller boards
• DMD shows lines or garbage and no controlled lamps light
• Dot matrix shows lines or lights solid, and no CPU lamps work
• Which DMD brands are hit by a blown lamp fuse
• The three Data East dot matrix display sizes
• Dot matrix controller CPUs by display size
• Swapping Williams and Data East alphanumeric displays

Source: Pinball Repair help group!! (Facebook group)