No picture but great sound

Is very possible your picture tube is good,the problem might be a loose conection in the main board,the circuits to check will be the horizontal driver transformer,the output transformer and all overheated components in that area,another possible reason might be a loose conection in the crt board witch is in the neck of the picture tube,if you are familiar with tv service you can try to repair it yourself,you can start by removing the back cover and try to tap on different areas of the chassis to see if it reacts ,do this with a wooden or plastic handle(not metal)and be atentive where you tap when the set reacts so you can go back and check the solder conections,if you are not too familiar be safe and call for help from a servicer.Let Us know if you need more information.