As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE, R-3 AUDIO CONTROL PANEL (PSS PWR) SWITCH SHORTED OUT CAUSING SMOKE. REMOVED THE UNIT. STORED UNIT IN COCKPIT. FOUND PSS SWITCH CONTACT BURNED. REMOVED AND REPLACED PSS SWITCH. CHECKED WIRING PER WDW 23-30-12. WIRING OK AND OPS CHECK PSS OK PER MM 23-34-00. ALL FUNCTIONS NORMAL. (X)