PRIMARY ELECTRICAL PWR SUPPLY PROB RESULTS IN EMER DECLARED AND DIVERSION TO ALTERNATE ARPT. GEAR COLLAPSES UPON LNDG PROC ROLLOUT.

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SUDDEN LOSS ELECTRICAL SYS WHILE IN FLT. ALL ELECTRICALLY OPERATED EQUIP FAILED; INCLUDING DIRECTIONAL GYROSCOPE; RADIOS AND XPONDER; EGT; DIGITAL FUEL GAUGES. BOTH VOR/OMNI INDICATORS NOT WORKING. FLEW DISABLED CRAFT TO DEST ARPT BY PILOTAGE; MAGNETIC COMPASS; IAS; ALTIMETER. ON APCH TO DEST (MODESTO); PERFORMED 'GUMPS'. HEARD LANDING GEAR LET DOWN BUT NO LIGHT INDICATING UNDERCARRIAGE LOCKED. I THOUGHT LIGHT MAY NOT BE WORKING BECAUSE OF ELECTRICAL FAILURE. MADE DECISION TO LAND BEFORE ANYTHING ELSE WENT WRONG (FEARFUL OF ELECTRICAL FIRE). I WAS PREPARED TO GAR; HOWEVER; IF ACFT FAILED TO TOUCH DOWN AT PROPER HT ABOVE GROUND. ACFT DID TOUCH DOWN (GENTLY); ROLLED OUT 75 YARDS OR SO. THEN UNDERCARRIAGE COLLAPSED. ACFT SLID ON UNDERSURFACE APPROX 75 YARDS AND CAME TO REST JUST OFF THE RWY ON THE L (GRASSY AREA). THIS PLT SLIGHTLY UNNERVED; BUT NO INJURIES. CAUSE OF ELECTRICAL FAILURE: UNKNOWN AT THIS TIME. CORRECTIVE ACTIONS: IMMEDIATELY DIALED 7700 ONE MIN AND 7600 FOR 15 MINS. PROBABLY USELESS PROC SINCE XPONDER LIGHT OUT. INACTIONS: I KNEW THE PROCS FOR ELECTRICAL FAILURE (CHK ALTERNATOR LIGHTS; ETC; ETC. IF BOTH ALTERNATOR LIGHTS OUT; SWITCH TO OTHER REGULATOR; ETC). HOWEVER; I THE ANXIETY OF THE MOMENT (WORRIED ABOUT ELECTRICAL FIRE) AND OPERATING THE ACFT VIA PILOTAGE; ETC; I FAILED TO EXECUTE THE EMER PROCS FOR ELECTRICAL FAILURE. IF I HAD; AND THE PROB WAS FAILURE OF ONE REGULATOR; I WOULDN'T BE FILLING OUT THIS QUESTIONNAIRE. ON THE OTHER HAND; INSPECTION OF THE ACFT DOWN THE ROAD MAY REVEAL EXECUTION OF ELECTRICAL EMER PROC WOULDN'T HAVE MADE ANY DIFFERENCE. I MADE WRONG ASSUMPTION THAT LNDG GEAR LIGHT WAS NOT WORKING BECAUSE OF THE ELECTRICAL FAILURE. I SHOULD HAVE MANUALLY LOCKED THE GEAR DOWN -- OR AT LEAST HAND CRANKED IT DOWN AS FAR AS IT WOULD CRANK. HOWEVER; WITH SO MANY GAUGES BLINKING ON AND OFF ALL OVER MY INST PANEL LIKE A PENNY ARCADE AND FEARFUL OF AN ELECTRICAL FIRE; I MADE THE DECISION TO GET THE ACFT ON THE GND AS SOON AS POSSIBLE; ESPECIALLY FEARFUL THAT THE ELECTRICAL FAILURE WOULD ERUPT INTO AN ELECTRICAL FIRE.