Hello all Marshall lovers, This is my JCM800 2203 in the video. The YouTube link below is will show my AMP error. I heard the sound like that a few days ago when I turn on my AMP. There is a noise whenever I knock with drum stick to the amp body and/or the circuit and no guitar sound is out. Like a loose connection, but I think it is not loose connection as the sound is there any where I hit with the stick. Please tell me if someone know what's happened? Thanks.