6С4С (=6B4G) directly-heated triode, made by Svetlana in 1978. This tube, along with its three sisters, is working in my push-pull monoblock amps (albeit not every day), at 300V on the plate, for almost a quarter of a century. So far so good.
<a href="//commons.wikimedia.org/w/index.php?title=User:Retired_electrician&amp;action=edit&amp;redlink=1" class="new" title="User:Retired electrician (page does not exist)">Retired electrician</a>
2022-12-31 22:25:22
<span class="int-own-work" lang="en">Own work</span>