PLT OF AN SMA SEL MISSET THE VOR RADIAL AND FLEW THE WRONG COURSE RESULTING IN ATC INTERVENTION.

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FOR UNKNOWN REASONS; I WAS NOT AS MENTALLY SHARP OR 'AHEAD OF THE ACFT' AS I NORMALLY TRY TO BE. I HAD MADE A NUMBER OF SIMPLE; EASILY CORRECTABLE MISTAKES DURING THE FLT PRIOR TO THIS ONE. WHILE DSNDING INTO PHILADELPHIA INTL; I WAS INSTRUCTED TO PROCEED VIA V-210 TO BUCKS INTXN AFTER XING LANCASTER VOR (LRP). THE RNAV WAS SET TO PERMIT DIRECT NAV TO BUCKS FROM LRP (104 DEGS AT 26 DME). HOWEVER; INSTEAD OF PLACING 104 DEG IN THE RNAV HDG INDICATOR; I HAD PLACED 140 DEGS. AFTER XING LRP; I NAVIGATED BY THE RNAV/HSI COMBINATION. AT APPROX 14 DME; THE PHILADELPHIA CTLR ASKED IF I WAS PROCEEDING TO BUCKS ON V-210. BELIEVING I WAS; I CONFIRMED THAT I WAS PROCEEDING TO BUCKS ON 210 (HSI CTRED). THE CTLR ISSUED A HDG CHANGE TOWARDS BUCKS. AT THIS POINT I DISCOVERED THE RNAV ENTRY MISTAKE AND INFORMED THE CTLR. I WAS DIRECTED TO PROCEED DIRECT BUCKS. NO OTHER PROBS AROSE. WHILE I WAS FIT TO FLY; I PERMITTED A STATE OF MENTAL UNPREPAREDNESS AND COMPLACENCY TO PREVAIL. HAD I CHKED AND RECHKED THE RNAV SETTINGS; THIS PROB WOULD HAVE BEN CAUGHT PRIOR TO XING LRP.