A BE35 PLT; TAXIING FOR TKOF; TAXIED PAST THE HOLD SHORT LINE.

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I WAS READY TO TAXI BONANZA XXXX AND GND CTL GAVE ME PERMISSION TO TAXI OUT TO RWY 35R AND HOLD SHORT. I REPEATED THE INSTRUCTIONS AND BEGAN TO TAXI. AS I TURNED ONTO THE TXWY; THE BUTTON ON THE TIP OF MY THROTTLE POPPED OFF BECAUSE THE SCREW HOLDING IT CAME LOOSE. ABOUT THAT TIME GND CALLED ME AND ASKED ME TO HOLD SHORT OF TXWY A8 IF NEEDED TO LET ONCOMING TFC CLR THE TXWY. I REPEATED HER INSTRUCTIONS AND ASKED PERMISSION TO GET OFF THE TXWY TO REPAIR THE KNOB. GND SAID THAT WAS OK. I EXITED THE TXWY AT TXWY A8. I PARKED NEAR THE END OF RWY 10 IN THE RUN-UP AREA. AFTER I REPAIRED THE KNOB; WHICH TOOK ABOUT 2 MINS; I CALLED GND AND RPTED THAT I WAS READY. GND SAID THAT I COULD PROCEED TO RWY 35R OR IF I WANTED RWY 10 I COULD DEPART TO THE SE. THIS WAS MY INTENDED DIRECTION OF FLT SO I OPTED FOR RWY 10. THE GND CTLR TOLD ME TO CALL WHEN READY FOR DEP AND TO REMAIN ON THIS FREQ. I MOVED L AND TOWARDS RWY 10 ABOUT 100 FT. I PARKED AND BEGAN MY FINAL RUN-UP PROC. ABOUT 1 MIN LATER; THE TWR OPERATOR CALLED 'XAX YOU HAVE CROSSED THE HOLD SHORT LINE AND ARE IMPEDING OP ON RWY 28/10.' IT TOOK ME ABOUT 5 SECONDS TO REALIZE WHAT HE MEANT AND AS I BEGAN TO ANSWER HE ASKED; 'XAX HOW DO YOU READ?' I SAID 'THIS IS XAX; I WAS TURNING AND PROCEEDING BEHIND THE HOLD SHORT LINE; WHICH I HAD CROSSED BY ABOUT 3/4 THE LENGTH OF THE ACFT.' I ADDED THAT 'I THOUGHT SHE (GND) HAD CLRED ME TO THE RWY AND TO CALL WHEN READY TO DEPART.' THE TWR SPEAKING AGAIN ON GND FREQ SAID 'NO; SHE CLRED YOU TO THE HOLD LINE.' I SAID 'I APOLOGIZE;' AND THAT 'I AM NOW BACK BEHIND THE HOLD LINE.' THE TWR; ON GND FREQ; SAID 'RPT READY TO DEPART.' I COMPLETED MY RUN-UP AND CALLED ABOUT 60 SECONDS LATER 'XAX READY FOR DEP.' THEY ANSWERED 'XAX MONITOR TWR AND WAIT FOR INSTRUCTION.' THERE WERE 2 ACFT ON FINAL; 1 ABOUT 1/2 MI OUT; THE OTHER ABOUT 2 MI OUT FOR RWY 28. WHEN THESE ACFT HAD CLRED THE RWY; I WAS CLRED FOR DEP ON RWY 10. I BELIEVE I WAS CONFUSED BY THE COMBINATION OF THE THROTTLE BUTTON COMING APART AND THEN THE UNEXPECTED CHANGE OF RWYS.