PA28-200R PLT ON IFR FLT PLAN IN IMC HAS TOTAL ELECTRICAL FAILURE. UNABLE TO NAV HE DSNDS TO VFR AND MAKES DIVERSION.

Narrative

DURING CRUISE AT 7000 FT IN THICK IMC AND RAIN AT HANDOVER HARRISBURG FROM 124.1 TO 126.45 FREQ; THE RADIO SYS STARTED TO EMIT A STEADILY INCREASING SCREECHING/SCREAMING HIGH PITCH SOUND OVERRIDING ALL RADIOS; DISABLING ALL COMS. SIMULTANEOUSLY; THE XPONDER STOPPED BLINKING. ALL OTHER ELECTRICALS WORKED. THIS DEVELOPED OVER A PERIOD OF 20 SECONDS. I XMITTED BLIND THAT I HAD SYS FAILURE AND SQUAWKED 7600. I CONTINUED ON MAGNETIC HDG OFF GYRO AT ALT BUT SLOWED DOWN. I WAS SE OF HARRISBURG; NW OF LANCASTER; W OF PHILADELPHIA AIRSPACE. ALL RADIOS LOST DISPLAYS AND WENT BLANK/DARK; INDICATORS RED-FLAGGED. WHILE CONTINUOUSLY XMITTING BLIND; FLYING THE AIRPLANE MANUALLY; I WAS GOING OVER MY CHKLIST AND SYSTEMATICALLY CHKING ALL SWITCHES AND THE BUS BAR. RECYCLING SWITCHES DID NOT HELP. AMMETER AND OTHER ELECTRICS LOOKED GOOD AND WORKED. PANEL LIGHTS WORKED. I SHUT OFF ALL ELECTRICITY AGAIN AND PULLED ALL FUSES. NOTHING WRONG. I SET ALL RADIOS TO OFF. SWITCHED THE AVIONICS MASTER TO OFF. SWITCHED ALL ELECTRICS ON; THEN THE AVIONICS MASTER TO ON. THEN ALL RADIOS AND NAVS BACK ON. XMITTED BLIND. WHILE DOING THIS FOR THE 4TH TIME; I REALIZED I COULD NOT NAV AT ALL AND STARTED A CTLED DSCNT IN THICK IMC AWAY FROM THE AIRWAYS; XMITTING INTENTIONS BLIND. I BROKE OUT AT 3000 FT MSL OVER FLAT FARMLAND. CONTINUOUSLY XMITTING BLIND. HAVING CONTACT WITH GND; I RESET THE SYS 3 MORE TIMES. THE 7TH TIME ALL RADIOS CAME BACK ON. I CONTACTED ATC AND EXPLAINED THE SIT AND I WAS 'NURSED' TO PTW AT 3000 FT. I SUSPECT OVERVOLTAGE OR A SHORT. NO OVERVOLTAGE LIGHT CAME ON. THE AUDIO PANEL LIT UP LIKE A CHRISTMAS TREE BEFORE TOTAL SYS FAILURE. IT COULD BE THE CAUSE. THERE WAS NOTHING AVAILABLE IN TERMS OF NAV EQUIP WITH WHICH TO CONTINUE MY FLT PLAN. I HAD NO MEANS OF NAV LEFT. UNLESS THE SYS COULD BE RESTORED; I HAD IDENTED AN EMER LNDG FIELD ON A FARM. PILOTAGE WAS OUT OF THE QUESTION. P.S. I HAVE ORDERED A HAND-HELD GPS COM TODAY.