Alim Tube Grundig TK8

Hi Audiogon forum,

I am new on the forum and in the repair domain, so sorry for a quite naive question. A neighbor was trashing a 1954 Grundig TK8 reel-to-reel tape recorder, so I saved it to restore it. I worked on it few months ago and disassembled it. With a multimeter, I convinced myself the issue came from one of the tubes being shot. That tube seems to be first tube in the circuit, the one receiving directly the juice. I made some researches online, downloaded the circuit and user manual, found the references of 4 out of 5 tubes, but unfortunately the missing reference is exactly the one I'm looking for...  

I have made accessible the user manual and circled the element that seems to have failed on mine - any help of any sort would be appreciated! 
https://www.dropbox.com/s/45v3xyexe6bm6wq/hfe_grundig_tk_8_service_de_circled.pdf?dl=0 

best wishes

Johnny