Inside the EF40 vacuum tube

Here’s a broken EF40 pentode tube. I dropped it, so took the opportunity to take a peek inside. The construction is intricate and quite beautiful.

Inside the EF40 tube, glass envelope removed

EF40 pentode with screen removed

EF40 with getter, mica insulation and plate removed

EF40 showing grids heaters and cathode have a good description of how tubes work, and this diagram from shows all the parts: