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Degassing tubes


Jim Gregory
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3 hours ago, Jim Gregory said:

What is the purpose of degassing tubes before testing ?

 

So the tube functions properly and then tests accurately.

 

I have never heard of anyone doing this before testing. If I get a tube that acts weird and tests gassy on a tube tester THEN I may try and activate the getter with an inductive heater to suck up the gasses and hopefully come back to life. It works but many times the tube just becomes gassy again because it has a compromised vacuum but it is well worth trying for very nice tubes you wish to not throw in the rubbish.

 

That's why they are called vacuum tubes, they don't work so well in an atmosphere of gas molecules floating around. 

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3 hours ago, captainbeefheart said:

So the tube functions properly and then tests accurately.

Thank You. Your explanation makes sense to me. I was looking at some RCA 845 tubes on eBay. The seller stated that the tubes had been degassed before testing. After reading your explanation, I would reason that the tubes before testing contained gasses that would have given a less favorable analysis outcome. And as you stated the tube can become gassy again. 

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Since USA NOS 845 tubes prices are ridiculous, I have used Chinese 845 tubes and they appear to perform well and sound great. If you are looking to retube or are building an amp, I would use these inexpensive tubes first, then if you think you still want or need USA NOS you can buy some, but I don’t think you will hear too much difference. 

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