[gregb]

That 6SC7 tube was most likely added as a phono preamp. I have seen that tube used many times in this application and it makes sense with the addition of the switch and RCA jack, most likely a low level input in conjunction with a high level input or maybe the switch just isolates the radio from the phono. As Terry pointed out not the best mounting location and they are usually mounted on isolated tube sockets as well. If you don't need or want a phono input, remove it all.

Gregb