Panasonic tv, tx-28ps1. sound is getting weaker, hiss on right speaker, left speaker sometimes fades with crackling. I checked all scart connections, tried a friends scart lead and makes no difference. Have opened back carefully. Speaker end connections are good. Havent touched the central area of circuit board (where speaker wires go to), for fear of electric shock. Has the amplifier started to die? Is it anything to with my cheap freeview set top box?