ON A B757-200 ON LEVELOFF AT 10000 FT IT WAS DISCOVERED THE CAPT'S AUDIO AND VHF COMS WERE INOP CAUSED BY A YOKE SWITCH FAILED IN THE XMIT POS. ACFT RETURNED TO DFW.

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AFTER TKOF FROM DFW WE WERE INSTRUCTED TO CONTACT DEP. THE FO WAS FLYING SO I SWITCHED FREQS. I TRIED SEVERAL TIMES TO CONTACT THEM WITH NO RESPONSE. I CHKED TO BE SURE THE CORRECT FREQ WAS SET. AFTER SEVERAL MORE ATTEMPTS; I SWITCHED BACK TO DFW TWR AND TRIED TO CONTACT THEM. WE REALIZED WE WERE NOT HEARING ANY XMISSIONS ON EITHER FREQ. THINKING THE L VHF WAS INOP; WE BOTH SWITCHED TO THE R VHF. WE WERE STILL UNABLE TO CONTACT DEP AND WE WERE NOT RECEIVING ANY XMISSIONS ON THE R VHF EITHER. WE LEVELED AT 10000 FT; OUR ASSIGNED ALT; AND SET THE XPONDER TO 7600. THE WX WAS VMC. WE MADE A TURN TO THE NW WITH AMA BEING THE FIRST POINT ON OUR RTE; BUT INTENDED TO RETURN TO DFW. I SENT A MESSAGE TO DISPATCH SO THEY COULD ADVISE ATC OF OUR INTENTIONS TO RETURN TO DFW. WE CONTINUED TO SWITCH RADIOS AND THE FO WAS EVENTUALLY ABLE TO CONTACT DFW TWR USING THE R VHF. THEY RELAYED BTWN US AND APCH CTL UNTIL WE GOT BACK INTO TWR'S AIRSPACE. I WAS UNABLE TO XMIT OR RECEIVE ON EITHER RADIO AND COULD ONLY HEAR USING THE FO'S SPEAKER. WE LANDED WITHOUT INCIDENT AND RETURNED TO THE GATE. MAINT DISCOVERED THE CAPT'S MIKE SWITCH INSIDE THE CTL YOKE WAS STUCK IN THE XMIT POS. THE SWITCH WAS REPLACED AND THE FLT CONTINUED TO HDN.