PLT RECEIVES NO RESPONSE FROM THE TWR; TAXIES ACROSS A RWY AND DISCOVERS THE RADIO VOLUME WAS TURNED DOWN.

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FOR THE PURPOSE OF PRACTICING VFR NIGHT LNDGS; I COMPLETED PREFLTS AND CALLED TCL GND FOR TAXI CLRNC TO RWY. AFTER 2 CALLS WITHOUT ANSWER A THIRD CALL WAS TRIED ON TWR FREQ; WITHOUT REPLY. AT ABOUT XA55 LCL TIME I ASSUMED THE TWR IS ALREADY CLOSED AND ANNOUNCED ON TWR FREQ TO TCL TFC; THAT I AM GOING TO TAXI FROM FBO TO RWY 22. BEFORE XING NON ACTIVE RWY 29 I DOUBLE-CHKED APCH PATHS IN BOTH DIRECTIONS AND ANNOUNCED VIA TWR FREQ; THE XING. AFTER HAVING CROSSED RWY 29 AND TAXIING TO THE ACTIVE RWY I RECEIVED A RED STOP-SIGNAL FROM THE TWR. I STOPPED IMMEDIATELY AND CHKED THE RADIOS. AFTER HAVING DIALED THE APPROPRIATE FREQS IN RADIO SET #2; I REALIZED; THAT VOLUME ON SET #1 WAS DOWN. THIS TURNED OUT TO BE THE REASON FOR NOT RECEIVING REPLIES FROM THE TWR. AFTER PROPER COM WITH TWR; I FOLLOWED A CLRNC TO TAXI TO RWY 22. AFTER BEING CLRED TO TAKE OFF; THE TWR SVC WAS TERMINATED AND I CONTINUED AGAIN WITH SEVERAL TA TO TCL TFC. IN DOING SO I COMPLETED 5 LNDGS AND A FLYING TIME OF 40 MINS WITHOUT ANYTHING UNUSUAL. RESUME: MY ASSUMPTION; THAT ACTIVATING RADIOS WITH THE MAIN SWITCH AND SUCCESSFULLY MONITORING ASOS ON SET #2 WILL IMPLY A PROPER FUNCTIONING OF SET #1 WAS WRONG; AS 'VOLUME' ON THIS SET WAS DOWN FROM A PRIOR PLT. MY DECISION TO TAXI AND CROSS A RWY AS A CONCLUSION OUT OF THE FACTS THERE WAS NO REPLY FROM TWR ON MY CALLS AND NO LIGHT SIGNAL FOR MINS OF TAXIING. WAS FALSE ALTHOUGH I DID TA TO OTHER TFC. MY JUDGEMENT THAT THE TWR CLOSES 5 MINS BEFORE HRS WAS FALSE. THE SIT DESCRIBED ABOVE IMPLIED NO OTHER ACFT.