AT ABOUT 1440 PDT, THE NON-INSTRUMENT RATED PLT DEPD ANTIOCH CA, ON A FLT TO BURBANK, CA. NO KNOWN IN-FLT COMMUNICATIONSWERE MADE UNTIL THE PLT CONTACTED TRACON AT 1725 PDT. AT THAT TIME, HE RPRTD INBOUND AT 7500' & REQUESTED A SPECIAL VFR CLNC TO THE ARPT. HE WAS TOLD TO MAINT VFR & WAS ADZD THE WX AT BURBANK (ELEV 775') WAS 700' OVERCAST WITH 1 MI VIS, FOG & LGT DRIZZLE. SEVERAL MINUTES LATER, COMMUNICATION WITH THE ACFT WAS LOST. SUBSEQUENTLY, THE ACFT CRASHED ON A RIDGELINE APRX 9 MI NNW OF THE BURBANK ARPT. IMPACT OCCURRED IN A SHALLOW, WINGS LEVEL DESCENT AT AN ELEVATION OF ABOUT 2600'. NO PREIMPACT PART MALFUNCTION OR FAILURE WAS EVIDENT. NO RECORD WAS FOUND OF A PRE-FLT WX BRIEFING. MTNS TOPS IN THE AREA WERE FORECAST TO BE OBSCURED; CLOUD TOPS WERE RPRTD AT 4500'. TRACES OF MEDICATION (METABOLITES OF CHLORPHENIRAMINE & BENZODIAZIPINE) WERE DETECTED ONLY IN THE PLT'S URINE; TOXICOLOGY TESTS OF HIS BLOOD WERE NEGATIVEFOR ALCOHOL & DRUGS.