The Quest for the missing tube

[LyMob]

Could anyone please tell me where is the 4th and last preamp tube of my tsl 602 ???? just the other day I opened the back of my marshall for my first ever tube change and I realised that there are 2 svet's on the power stage and only 3 preamp tubes!!!! according to marshall's site there should be 4 preamp tubes.....is this a "normal" situation?????
thx

[y2stevo]

Re: The Quest for the missing tube

There should be another one covered by a metal cylinder, i believe that it the V1 pre tube..