How can I identify a vault on my sony digital camcorder?

I have a sony digital camcorder (DCR HC-19E) which was working great until recently. The problem i have is this, if I open the viewing screen located at the side of the camera more that a quarter of the way out I lose the picture. I also have no sound when I play back a recording. If I connect the camera to the mains supply the picture is restorded but there is still no sound. I initially suspected a fault with the battery but I'm not so sure now. Any useful advice would be most welcome.