MY SHARP 20 INCH COLOR TV GIVING NOISE IN SOUND?

Question

TV CREATING NOISE SOME TIMES. IF I CHANGE CHANNEL DISTERBANCE WILL COME . THEN IF I FINE TUNED MANUALLY OK OR I HAVE TO TOUCH TUNER PLUG . SOME TIME PICTURE AND SOUND WILL BE SMOOTH.NO DRY SOLDER IN TUNER CARD.
WHAT IS THE PROBLEM. BUT IN AV MODE 100% OK.

IS IT TUNER PROBLEM?
IF SO, WHICH TUNER CARD I SHOULD PUT?
ANY ADJUSTMENT IN VOLTAGE ?