As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OBSERVER ACP INOPERATIVE. CANT CHANGE SELECTED TRANSMIT SWITCH. ACP FROZEN UNABLE TO SELECT ANY MIC ON OBSERVERS AUDIO CONTROL PANEL. REMOVED AND REPLACED OBSERVER ACP PER AMM 23-51-01. OPS CHECK GOOD. NO DEFECTS NOTED. ACFT OKAY TO CONTINUE.