Broken tube in guitar amplifier?

Hi, i have a peavey 5150 and its not working properly...when i try to play thru it i can barely hear the guitar at all, im thinking one of the tubes is blown because it is really old. is there a way i can tell by looking at the tube if it is blown or not? also there is a spring like noise whenever i shake the amp a little bit, i think that is the coil for the reverb unit? is this normal for it to be making that sound when i shake it a little bit?