What was found
ON CLIMBOUT FROM CLT, EN ROUTE TO RDU, CREW LOST ALL THREE RADIOS FOR A FEW MINUTES. THEN THE NR 1 RADIO CAME BACK TO SERVICE. FLIGHT RETURNED TO FIELD AT CLT AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE VERIFIED DEFECTIVE OBS AUDIO SELECTOR PANEL. REPLACED OBS AUDIO SELECTOR PANEL ASSEMBLY AND OPERATIONAL CHECK ACCOMPLISHED SATISFACTORY. REFERENCED MM 23-51-21, PAGE BLOCK 4, APPLICABLE PROCEDURES.