RCA tube #UY-227 question
 

Hi All,
I have a few N.O.S. RCA UY-227 tubes. Is there any use for these anymore or am
I holding onto them for no good reason? Are they worth anything at all? I think
that several years ago, I heard them referred to as "heater" tubes. I didn't
know that anything got hotter than a good old metal 6L6 tube....
rgds,
Mark S.