Jim Gregory Posted November 15, 2021 Share Posted November 15, 2021 What is the purpose of degassing tubes before testing ? Quote Link to comment Share on other sites More sharing options...
captainbeefheart Posted November 16, 2021 Share Posted November 16, 2021 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. Quote Link to comment Share on other sites More sharing options...
Jim Gregory Posted November 16, 2021 Author Share Posted November 16, 2021 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. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted November 16, 2021 Share Posted November 16, 2021 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. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted November 16, 2021 Share Posted November 16, 2021 I’ve used these in the past as an example. The new PSvane 845’s appear to be well made and are about $150 a pair. 1 Quote Link to comment Share on other sites More sharing options...
Shiva Posted November 16, 2021 Share Posted November 16, 2021 Just landed on this vid the other day and seems appropriate. Here she is talking about why vacuum and all about the Getter. 1 Quote Link to comment Share on other sites More sharing options...
Curious_George Posted November 16, 2021 Share Posted November 16, 2021 10 hours ago, Jim Gregory said: The seller stated that the tubes had been degassed before testing. If a vacuum tubes need anything done to it before you use it (except if you want to match them for various reasons), be wary. 1 Quote Link to comment Share on other sites More sharing options...
Jim Gregory Posted November 16, 2021 Author Share Posted November 16, 2021 6 hours ago, Curious_George said: I have used Chinese 845 tubes and they appear to perform well and sound great. I use Psvane 845 in my amps and they do great. I just got the itch to upgrade. Quote Link to comment Share on other sites More sharing options...
Curious_George Posted November 16, 2021 Share Posted November 16, 2021 Understood. Perhaps look elsewhere in the audio chain to spend money on the "upgrade". Unless you have money to burn. I'm not hurting for money, but I always look for a good value. It's just me. In addition, because I have so many hobbies, it helps spread the money around! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.