First day of running our air conditioner. When the air conditioner turned on a loud buzz and vibration in the conduit occurred in a pulsing rhythm fast at first then slowed and the stopped. Happened only once. Has not happened since. Additionally the power to our tv went out momentarily but did not trip the breaker. it appears that the conduit leading to the AC unit also contains the lines for the outlet for the TV. Finally ac unit is a rheem and is over 20 years old. Thoughts?