The left speaker keeps cutting out. Pressing on the sound board connectors or knocking the backbox brings it back for a while. The speaker and wiring check good and reflowing the header pins didn't help.

Speaker cuts out when the backbox is knocked: badly soldered op-amps

Cause: Two LM833 op-amps on the sound board had poor solder joints.

Checks

• Continuity-check the connectors and wiring to rule them out.
• With a magnifier, inspect every solder joint on the sound board, not only the headers, and look for hairline cracked traces.

Fix

• Resolder (or replace) the faulty LM833 chips; here the board went to a repairer.

Systems

• Data East CPU Version 3

Games

• Tales from the Crypt

Related tips

• Sounds suddenly come out wrong even with new ROMs: bad ribbon cable
• Speech distorted or wrong and sound cuts out: leaked C30 corroded the voice ROM
• Loud hum from the speakers
• Sound board power input connector CN2

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