Screen Full of Zeros With Irregular Black Blocks

Repair Case Summary

This page documents a firsthand Screen Full of Zeros With Irregular Black Blocks repair case. It is intended for technicians and collectors troubleshooting original Pac-Man or Ms. Pac-Man arcade PCB hardware.

• Date: 2017-04-07
• Board: Original Pac-Man PCB
• Category: Scratchpad RAM / boot failure
• Symptoms:
  • Startup screen full of 0s.
  • Irregular blocks of black space appeared among the zeros.
• Diagnostic observations / tests:
  • All scratchpad RAM from 4R through 4K was temporarily replaced with a known-good set and the board booted.
  • The removed 2114 RAMs were tested individually.
  • The failure could be reproduced with the bad RAM installed at 4K.
• Components / locations investigated: 4R-4K scratchpad RAM, 4K, 2114 RAM
• Root cause: One bad 2114 scratchpad RAM, originally at 4K.
• Repair: Replaced the bad 2114 RAM.
• Result: The board booted normally.
• Search terms: Pac-Man screen full of zeros; 0s on screen; black blocks; 2114 RAM; scratchpad RAM; 4K; 4R; boot failure
• Evidence: Physically verified repair / firsthand repair log

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

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• Screen Full of Red 2s Caused by Loose Sync Bus Controller
• Dead Board, Watchdog Running, Broken Traces at 3S

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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