BONANZA PLT ASSUMED TWR WAS CLOSED WHEN NO RESPONSE WAS RECEIVED FROM HIS RADIO TRANSMISSIONS. AS HE TAXIED ONTO THE RWY; HE DISCOVERED THAT THE TWR WAS OPERATING; BUT HIS RADIO VOLUME WAS TURNED DOWN

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I AND 3 OTHER GUESTS WERE READYING FOR A DEP. I LOADED PAX; MY NEIGHBORS; FOR THEIR FIRST FLT WITH ME. I BRIEFED THEM ON THE ACFT AND THE EMER EGRESS PROC FOR MY BONANZA. I THEN STARTED THE ENG AND LISTENED TO THE ATIS. I THEN CALLED ADDISON GND AND ADVISED THEM THAT I WAS REQUESTING FLT FOLLOWING AT 3500 FT. THERE WAS NO RESPONSE. I THEN CALLED AGAIN; TO NO RESPONSE. I CONCLUDED THE TWR WAS NOT OPEN YET. THOUGH I HAD CHKED THE NIGHT BEFORE ON A WEBSITE TO LEARN THE TWR OPERATING HRS; IT WAS DARK AND THERE WAS NO ACTIVITY AT THE ARPT. I THEN SWITCHED TO THE TWR FREQ ON THE SAME RADIO AND CALLED THE TWR. THERE WAS NO RESPONSE. SO I FIGURED I GOT THE HRS OF OP WRONG. I DECIDED TO TAXI AND ANNOUNCE MY INTENTIONS AS THE ARPT TWR WAS CLOSED. I ANNOUNCED TAXIING TO RWY 33. AT THE DEP END I COMPLETED MY ENG RUN-UP AND BEFORE TKOF CHKLIST. I THEN ANNOUNCED MY DEP TO AREA TFC ON THE TWR FREQ AND ALSO MENTIONED I WOULD BE A N DEP. I THEN TAXIED ONTO THE RWY FOR DEP. AS I LINED UP ON THE RWY I NOTICED IN THE DARKNESS A BRIGHT RED LIGHT SHINING AT ME FROM THE CTL TWR. I WAS STARTLED THAT ANYONE WAS IN THE TWR. I QUICKLY TAXIED OFF THE RWY. I STOPPED AND THEN PUT THE TWR FREQ IN THE #2 RADIO. I CALLED THE TWR AND THEY IMMEDIATELY RESPONDED TO ME. THE TWR CTLR SAID HE HEARD ALL OF MY CALLS. THEN HE SAID DON'T WORRY ABOUT IT AND YOU ARE CLRED FOR TKOF; HAVE A GOOD TRIP. I THEN WENT TO MY #1 RADIO AND DETERMINED THE VOLUME WAS TURNED ALL THE WAY DOWN. I COULD NOT BELIEVE IT. I NEVER QUESTIONED THE POSSIBILITY I HAD A RADIO ADJUSTMENT PROB. I HAD GONE TO THE ARPT PREVIOUSLY AND SAT IN THE AIRPLANE TO PRACTICE USING MY NEW GARMIN 496 GPS. I TURNED MY RADIOS ON WITH THE AVIONICS MASTER SWITCH. WHILE I WAS PRACTICING WITH MY NEW GPS I HAD TURNED OFF ALL OTHER AVIONICS INDIVIDUALLY TO REDUCE THE BATTERY DRAW. AFTER 20-30 MINS OF REVIEW ON THE NEW GPS; I TURNED ON ALL THE AVIONICS INCLUDING THE #1 GARMIN 430; BUT I MUST HAVE JUST TURNED IT ON AND I DID NOT ADJUST THE VOLUME. I THEN TURNED OFF THE AVIONICS MASTER SWITCH. I HAVE A PARTNER IN THE ACFT; BUT HE HAS NOT BEEN TO THE AIRPLANE SINCE I WAS LAST. I DID NOT QUESTION THERE WAS ANYTHING WRONG WITH THE #1 RADIO. I MADE THE INCORRECT ASSUMPTION THE ARPT TWR WAS CLOSED. MY DIRECTION FROM THE TWR WHILE TAXIING WAS AWAY FROM THE TWR; AND ONLY WHEN I TURNED ONTO THE RWY WAS I LOOKING TOWARD THE TWR. IN RETROSPECT; IT SHOULD HAVE TUMBLED TO ME THE TWR WAS OPEN BY THE FACT THAT ATIS WAS ON. MY ONLY EXPLANATION FOR THIS IS I FLY PROFESSIONALLY FROM ANOTHER LCL ARPT. AT THAT ARPT THEY HAVE AN ASOS. IT ALWAYS IS ON WHETHER THE TWR IS OPERATING OR NOT. WE ALSO HAVE OPS THAT DEPART BEFORE THE TWR OPENS IN WHICH WE JUST ANNOUNCE OUR INTENTIONS ON THE TWR FREQ. IT WASN'T UNTIL THAT NEXT EVENING DID I EVEN THINK ABOUT THE ATIS AND HOW THAT SHOULD HAVE TIPPED ME OFF TO THE TWR BEING OPEN.