Chevrolet Repair: chevy hei dist buzzes

Question
i have a 67 chevy c20 with a 82 caprice 350 motor with hei ignition motor been i n truck for min. 15 years.Recently started draining batt.Also buzzing noise heard in coil. I can disconnect battery cable or hot wire to hei ,buzzing quits does not drain battery until i start truck then shut off , buzzing starts again . Replaced ignition switch,coil, dist.cap, rotor.Very confusing. Can capacitor cause this problem? What is my cure?

Answer
HI DAVE, A 67 CHEVY TRUCK NICE !!!! I DO NOT THINK A CAPACITOR WILL CAUSE THIS...DOES THIS HAVE THE 67 HARNESS TO THE DIST STILL AND SWITCHED TO THE NEW HEI SYSTEM ??? WOW THIS IS A GOOD ONE.. OK HANG TIGHT I WILL GET BACK TO YOU ON THIS ONE. I HAVE SOME OLD TIMER TECHS THAT I THINK WILL KNOW THIS....[[[I WILL GET BACK TO YOU ON THIS IN 1 OR 2 DAYS I WILL NOT FORGET THIS...TOM...
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GOOD MORN DAVE,I WAS UNABLE TO REACH A FRIEND OF MINE ON THIS WEIRD PROBLEM. HE IS A ELECTRONIC GURU WITH STRANGE PROBLEM.....BUT I HAVE HAD SOME TIME TO THINK ABOUT THIS..THE BUZZING IS FROM THE COIL  AND I BET THAT THIS IS HAPPENING BECAUSE THERE IS A WEAK VOLTAGE SUPPLY TO THIS AFTER THE KEY IS OFF CAUSING THE BUZZ. HAVE YOU HOOKED ANYTHING UP TO THE COIL MAIN VOLT SUPPLY IN THE PAST LIKE TACH, RADIO WHATEVER ???? IF NOT THEN I ASKED YOU LAST NIGHT DOES THIS STILL HAVE THE ORIGINAL HARNESS FROM THE 67 ??? BECAUSE IF SO THIS HARNESS HAS A BUILT IN RESISTOR IN IT TO LOWER THE VOLTAGE TO THE POINTS WHEN RUNNING.SO I WONDER IS SOMETHING HAS BURNED OUT IN THE HARNESS..SO TO TEST MY THEORY GET A VOLT METER AND CK FOR VOLTAGE TO THIS COIL WHEN THE KEY IS OFF. I BET YOU WILL FIND THERE IS LOW VOLTAGE TO IT..LIKE 5 TO 7 VOLTS MAYBE. SO IF THIS IS THE CASE FIND OUT WHERE THE POWER WIRE IS GETTING FED THIS POWER SUPPLY..OR RUN A NEW WIRE FROM THE SWITCH TO THE COIL..ONLY IF THIS IS THE PROBLEM...PLEASE LET ME KNOW IF I AM ON THE RIGHT TRACK..GOOD LUCK TO YOU,,,TOM....