Robotron repair log – Sound channel missing


Repair cost:  $5

KLOV post:

Symptom: Some sounds missing

Diagnosis: Self test diagnostic indicates no sound on Line 3.  Check sound board logic.


  • 9/23/09 – Tons of cold solder joints, pins barely holding in.  Resoldered all connector headers on all boards.  No change.
  • 9/28/09 – Jiggled 2J3, 10J3 connectors (ROM board to sound board), no change.
  • 10/21/09 – Check sound board with logic probe, pin 12 on PIA stuck high.  Traced back to the J4 connectors (from ROM to sound bd), all the way back to PIA on ROM board, which supplies the signal.  Pin 12 stuck high & never pulsed low when I put sound test into Line 3.  4.7K pullup resistor DIP package tested good, so confirmed the chip is bad.  PIA chip on order from Bob Roberts.
  • 10/24/09 – Replaced PIA on ROM board.  Sound lines all present in diagnostic screen & game sounds play fine.

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