Monday, October 19, 2009


Ever see a power tube getting rebuilt? Didja know it could be done? One of my favorite tube rebuilders, Kennetron, has a bit of a virtual tour of their plant!

Sure, there are other rebuilders; many years ago, I used Econco for big Class C power tubes in FM service (now a wholly-owned division of CPI, which also owns Eimac, it looks like they have dropped their old, irreverent "use a transistor, go to jail" tagline) and I've always heard good things about Freeland Products. Still, I have a soft spot for Kennetron, who have so far been the only outfit willing to take on rebuilding small (1000 Watt!) ceramic external-anode power tetrodes used at ultra high frequencies in Class AB1 -- and their rebuilds work! This is a fussy task, combining the skills of jeweler, machinist, welder and more for devices that operate in about the same power range as chainsaws.

It's a heck of a thing to send in old, worn-out, even shorted "empties" and get 'em back at half the price or less of new tubes, ready to go.

Power tube rebuilders are a scarce breed. The collection of skills and equipment to do the job, from vacuum engineering to glass building to fabricating the intricate internal assemblies, is rare and unlikely -- we're lucky there are at least three left!


  1. When I worked for DirecTV we used CPI to rebuild our Ku-Band Klystrons. We always kept a few in the spares room, but also sent the dead/weak ones in as soon as we pulled them, as it could take them a while to rebuild them. I think they said they did them in batches, and if you sent one in "out of turn", it could take months to get it back.

  2. I've put Econco tubes in at 105.7 and 92.1 with no issues. We went to a Svetlana tube in the early 90's in the Continental 25KW FM at 92.1.... And it didn't like that low a frequency. Not sure why.... 4CX15000A.. as I remember.....

    Thanks for the memories. I'm really enjoying walking thru you blog!!


  3. Thank you! --I just checked for new comments today; didn't mean to leave yours in limbo.