BE55 ON A FERRY FLT HAS LOSS OF COM RADIO WHILE APCHING TRI CITY; TN. PLT ATTEMPTS TO AVOID CLASS D AIRSPACE FOR A RETURN TO DEP ARPT BUT CLIPS THE EDGE OF TRI AND HAS AN NMAC WITH AN ACR ON APCH. RPTR NEVER SAW THE OTHER ACFT.

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I WAS ON A FERRY PERMIT IN A 1962 A55 BARON (VFR ONLY). I TOOK OFF FROM JOHNSON CITY; TN; ENRTE TO SAN DIEGO; BROWN FIELD. JOHNSON CITY ARPT HAD NO FUEL; SO I DECIDED TO GO TO TRI CITY FOR FUEL. I RECEIVED ATIS FROM TRI CITY ARPT AND SWITCHED TO TWR FREQ. I COULD NOT RECEIVE OR XMIT ON COM FREQ DUE TO THE RADIO OVERHEATING AND EVENTUALLY SHUTTING OFF. SO I THOUGHT MY BEST DECISION WOULD BE TO FLY BACK TO JOHNSON CITY; SO I MADE A 90 DEG TURN FROM MY APCH ANGLE AND FLEW AROUND THE CIRCUMFERENCE OF THE CLASS D AIRSPACE. APPARENTLY; I PENETRATED THE CLASS D AT TRI CITY BY 1 MI; AND MISSED A MIDAIR BY SOME 300 FT WITH ANOTHER ACFT ON APCH. I NEVER SAW THE OTHER ACFT. I KNEW I WAS CLOSE TO PENETRATING CLASS D; SO I DECIDED THAT SINCE MY RADIO WAS INOP AND TO AVOID TFC PROBS AT TRI CITY; THAT IT WOULD BE SAFER TO AVOID INCOMING TFC THERE AND JUST FLY BACK TO JOHNSON CITY. THERE I WAS GREETED BY A POLICE OFFICER AND HE TOOK MY PLT INFO AND ADVISED ME TO CALL THE TRI CITY TWR. I CALLED THE TWR AND WE DISCUSSED THE SIT TOGETHER. I'VE BEEN FLYING IN THE SOUTHERN CALIFORNIA AREA ALL MY LIFE AND HAVE NEVER VIOLATED AN AIRSPACE. I SHOULD HAVE AVOIDED CLASS D AIRSPACE UNTIL COMS WERE MADE. MY OPINION OF WHAT MECHANICALLY HAPPENED IS THAT SINCE IT HAS BEEN A YR SINCE THE RADIOS HAVE BEEN TURNED ON THEY OVERHEATED AND SHUT OFF. THE SOLUTION TO ALL OF THIS WOULD BE TO CARRY A HAND-HELD RADIO ON MY FERRY FLTS.