So I run a recording studio and allow bands to use the drum room as a rehearsal space, Last night a band knocks on the control room door and says the bass amp has stopped working, thats rather odd as its a Simms Watts AP 200 super and has been fully recapped with hi quality caps and like old Matamps those amps don't fail very often. So I check the fuses and discover a blown Mains fuse and see that one of the sprung string nets that hold the output tubes (GEC KT 88 Date code 7210 thats 1972 october) in their sockets, is lying by the side of the second from left tube with a broken spring and the tube is cracked just on the turn of the glass body at the back just where the spring might have hit the tube if the spring broke. The spring was stainless steel. So thats the cause of failure. A broken valve retaining spring?, still I have a Roost amp until I can find another good new old stock GEC KT 88, any one have a good one they want to flog?. PS It makes me wonder if someone tried to pull one of the tubes as I leave the back off to improve ventilation and so I can see the tubes clearly from the control room window, its not that hard to get round the back of the stack, perhaps I should make it harder?. Or do stainless steel springs under gentle tension just fall in half and crack tubes?.