The T-Rex head turns in one direction only and never comes back the other way.

T-Rex only moves one way: broken wire at the relay coil on the motor board

Cause: One of the direction relays on the T-Rex motor board never pulled in: the fine wire had broken away from the relay coil's terminal under the intact cover.

Checks

• Run the T-Rex in test and watch or listen for each relay on the motor board pulling in.
• Take the cover off the relay that stays still and look for a broken coil lead; also check its contacts are not bent so far apart that they barely touch.

Fix

• Replace the relay (or the board).
• As a stop-gap, the broken coil lead can be carefully rejoined to its terminal with solder, and lightly bent contacts adjusted so they close firmly.

Systems

• Data East CPU Version 3

Games

• Jurassic Park

Related tips

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