As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3900 THE CREW REPORTED THE FLIGHT ATTENDANT CALL BUTTON LIGHTS FOR ROWS 7, 8, 9, 10 CAME ON UNCOMMANDED FOLLOWED BY REPORTS OF FUMES AND POSSIBLE LIGHT SMOKE. LIGHTS REMAINED ON UNTIL AIRCRAFT POWERED DOWN. THE AIRCRAFT WAS REMOVED FROM SERVICE. FOUND BURNT PCB CARD AT SEAT 7BC. REMOVED AND REPLACED THE PCB CARD IAW EMB MM 33-25-04. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.