PLT OF SMA ACFT LOST ALL RADIO COM AND NAV DURING AN IFR FLT.

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LOST COMPLETE COM/NAV IN VMC ABOVE BROKEN OVCST. MADE DECISION AND IMMEDIATELY PROCEEDED VIA MAGNETIC HDG TOWARD BTV AS BTV IS USUALLY BETTER WX THAN INTENDED DEST OF MPV (DEPARTED MHT). AS I GOT CLOSER I COULD TELL THAT I WOULD NOT BE ABLE TO SEE BTV; HOWEVER; I DID FIND AN AREA WHERE I COULD SEE THE GND. I DECIDE TO REMAIN IN THAT AREA AS THERE WERE NUMEROUS PLACES THAT APPEAR SUITABLE FOR AN EMER LNDG. I HAD 3.5 HRS OF FUEL AT THAT POINT AND DECIDED THAT I WOULD LAND WITH 1 HR OF FUEL. NOTE: AT FIRST NOTICE OF FAILURE; I DECLARED EMER AND SQUAWKED 7700 1 MIN AND 7600 15 MINS ALTERNATELY. REMAINING IN VISUAL CONTACT WITH GND; I BEGAN TROUBLESHOOTING; RECYCLING CIRCUIT BREAKERS; BATTERY SWITCH; ALTERNATORS; RADIO MASTER; STANDBY RADIO MASTER; ETC -- NO HELP. AFTER APPROX 15-20 MINS; I TURNED OFF BATTERY FOR 10-15 MINS. WHEN I REENGAGED BATTERY; ALL EQUIP WAS WORKING AND I FOUND I WAS 17.5 DME E OF BTV. I CONTACTED BTV APCH AND WAS VECTORED; DSNDED TO ASR RWY 15. I INFORMED APCH CTLR OF INTENTIONS TO OBTAIN VISUAL CONTACT AT ALTERNATE AND HDG ASSIGNED AND LAND VISUALLY IF COM WAS LOST AGAIN. LNDG WAS MADE; NO FURTHER PROBLEMS.