Slightly Distorted Sound Effects and Intermission Music

Repair Case Summary

This page documents a firsthand Slightly Distorted Sound Effects and Intermission Music repair case. It is intended for technicians and collectors troubleshooting original Pac-Man or Ms. Pac-Man arcade PCB hardware.

• Date: 2017-06-17
• Board: Original Pac-Man PCB
• Category: Sound
• Symptoms:
  • Background siren was slightly distorted.
  • Intermission music was slightly distorted.
  • All test-mode sounds were audible but distorted.
• Diagnostic observations / tests:
  • Replacing the volume switch produced no change.
  • Swapping 1N produced no change.
  • Working backward through the sound circuit led from 1N to 2M to 1M.
  • 1M was factory socketed, so it was swapped.
• Components / locations investigated: Volume switch, 1N, 2M, 1M
• Root cause: Fault at 1M.
• Repair: Swapped the device at 1M.
• Result: All sound effects became distortion-free and clear.
• Search terms: Pac-Man distorted sound; distorted siren; intermission distortion; 1M; 1N; 2M; sound circuit
• Evidence: Physically verified repair / firsthand repair log

Related Pac-Man / Ms. Pac-Man Repair Cases

• Missing and Out-of-Tempo Sounds From Broken Trace at 1M
• Crunchy and Fuzzy Sound Effects
• Missing Background Siren and Hum With Aftermarket Ms. Pac-Man Daughter Card
• No Sound: Signal Trace Leads to 74LS139 at 7M

How to Use This Repair Record

This is a firsthand physical repair case. The same symptom on another Pac-Man or Ms. Pac-Man PCB can have a different electrical cause. Use the documented diagnostic observations and tests to guide troubleshooting rather than replacing a component solely because it repaired this board.

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