That is it. You need at least a few seconds, To seal the leaks. If the leak is to big, you can make the leak smaller and repeat the Vacuum process. Big leaks, like when you drill a unused pin out, are a bit harder to seal. But a bottom entry is good, for straightening the elements, Just harder to seal. It all depends on the tube in hand.
This talk about restoring a vacuum in a tube has got to be a joke, right? When Eimac closed the Salt Lake City plant, they had to cut up with torches the huge rotary vacuum pumps because they were so big and heavy they could not move them. And you people think you can remove air from a tube? That is shear non sense.
Shear away. People do it all the time. All you need is a vacuum pump and a vacuum chamber. I maintain a couple of vacuum tubes with built in vacuum pumps. They can be "de-evacuated" for internal service at any time.
I guess it is, see to believe. I tested using lightbulbs before trying tubes, Then I got a better pump for tubes. The pump I have to do tubes will suck a Light bulb in, Just because of the thin glass. A good pump is key, To do it right.
That not reason they were cut up. They moved them in originally. Likely did not want anyone to have them.
OK I'm trying to put this whole thing together and then I thought of the recent thread by KB4MNG about his 4-400 turning blue. Consensus was his tube had gained some gas. I'm thinking then that this tube might have been a good candidate for a vacuum chamber session. So, questions I have and please answer in simple terms that assume young grasshopper (me) has little knowledge and is trying to learn. Cause I don't and I am: How long should tube be in the chamber under vacuum? How do you even know your chamber has achieved a better vacuum than what's inside the tube? Because if your chamber vacuum pressure isn't lower then inside the tube...you got nothing. How do you determine where the leak is? Still not getting that part. Does the hard as nails not react or melt or something at high heat when tube is under heavy use?
