As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FIRST OFFICERS OXYGEN MASK MICROPHONE WILL NOT TRANSMIT TO FIRST OFFICER SPEAKER. SWAPPED ASP WITH 1ST OBS NO HELP. REPLACED F/O'S OXYGEN MASK, NO HELP. REPLACED AUDIO ACCESS UNIT, NO HELP. TROUBLESHOT DOWN TO BAD F/O'S SPEAKER. BOX FOR F/O'S OXYGEN MASK WAS ALSO REPLACED, NO HELP. NOT MR UNIT. ADJUSTED, SYSTEM CKS NORMAL.