Quote:
Originally Posted by Von Soundcard /img/forum/go_quote.gif
Actually it was more of a pun to your last reply
5000-7000 hours does sound a bit optimistic, from what I've heard it could be perhaps half of that; however it all depends on what the figure means: is it the degradation of it's response below certain values or total lifetime until failure.
Even though the manufacturers may not have usually provided life expectancies for the tubes, they could have done so for the military versions - in which case they may lay somewhere in an army manual or spec.
However, the best advice would indeed come from a professional who has worked with this tube and knows it's limitations.
But you see, whenever we get into serious territory and someone brings a significant issue to the table - one which may involve hard gained knowledge or even trade secrets - all the 'gurus' suddenly have something else to do and you're left with Google
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I understand the importance of answering your question, but you will get mixed results.
You have to remember these tubes are up to 60 years old, and may have never been used. It could die on you the next day you have it. And because of the nature of tubes, we kind of average what the well respected have to say, and get from 1,000-8,000 hours. Since they are so old, there is no concrete evidence saying one tube WILL last "X" amount of hours. My advise to you, buy multiple replacements, that way you will always have one hand.
You could have 10 of the same tubes, with 4 failing under 1,000 hours,4 failing between 2,000 and 6,000, and you may find the rest of your tubes average 7,000+ hours.
It is too dependent on the source, and the tube. I don't know how much more you want. Dare I say to use Google, but I bet I can help you out with specifics, but it would be with the use of Google, which it seems your not to fond of.
Maybe this book would help you:
Amazon.com: Customer Reviews: Power Vacuum Tubes Handbook, Second Edition (Electronics Handbook Series)
Check with your local library. I am not having too much luck, as most everything I am reading says "too many variables in play".
In all honesty, just image 2,000-4,000 would be an adequate amount of time.
Just register here:
Tubes Asylum
And ask away. Some of those guys are true tube nuts; if you can't pull the answer you're looking for, you may not ever know. These are some of the most knowledgeable people in the Tubes department, I know.
Good luck..
-Nick