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Does tube testers tell how much life is left for tubes?

Let's say that you have new tubes, very old tubes that are almost to die, and something in the middle.
What kinds of reading do you expect from these three kinds?
Can you usually tell the life of tubes from tube testers?
How about the color? Do those three kinds of tubes have different colors when they were turned on?
I would like to know when to change tubes before it gets too late.
Some says if it sounds good, don't bother to change. 
Some brands of power/pre amps consume more on tubes than other brands and their life seems varies brand by brand. 
128x128ihcho
ihcho's avatar
ihcho OP
612 posts
 
Thanks for the info (even to MC).
I have two tube testers. One from Knight and one from Superior Instrument. Both is I guess made in late 50s or early 60s. They don’t have transconductance readings. They tell whether tubes are good or bad, but they don’t tell how much life is left.
If in doubt, I would just purchase new tubes to be safe.
The new (old) preamp I just bought (A.I. M3B) is recommended to have tubes replaced every two years. Yikes!

jjss49's avatar
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jjss49
6,612 posts
 
short answer is even the best tube testers measure the present degree of mutual transconductance of a test subject tube - it is a decent proxy for tube strength/freshness but it is a poor proxy for durability as a function of time

if you want to educate yourself more...

http://www.alltubetesters.com/articles/tester_guide.htm

http://www.jacmusic.com/Tube-testers/

https://shop.ehx.com/vacuum-tube-faq/ - see section on tube testing
ninetynine's avatar
ninetynine
135 posts
 
I use the uTracer and i am happy with it. Most important for me is transconductance.Only in German, sorryhttps://www.orangeaudio.de/blog/2021/04/29/roehrenmessung-mit-dem-utracer/
don_c55
1,025 posts
 
An approximation of tube life can be found from the cathode emissions, which I think some testers can provide.

When the cathode electron emission drops way low the tube is at the end of its life.

Tubes can test good right up to the end time of failure.
mijostyn's avatar
mijostyn
8,570 posts
 
RIght, the testers can tell you whether or not the tube is OK. They can not tell you how much time is left on the tube until the tube starts to measure poorly which means the tube is at deaths door. I use tubes until they fail and in my experience they sound just fine until they do fail. 
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