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Post by mrpharmacist on Mar 20, 2011 9:26:23 GMT
Hi all, I was wondering when you can gauge tubes are at the end of their life. I've got some Raytheon 12AX7A's and they seem to be losing some bass and seperation and getting noisier ie more 'hiss'. A second question is with the V3 switched on to warm up, is the tubes lifespan being used up regardless of playing music or not? Cheers~
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Post by PinkFloyd on Mar 20, 2011 11:11:41 GMT
Hi all, I was wondering when you can gauge tubes are at the end of their life. I've got some Raytheon 12AX7A's and they seem to be losing some bass and seperation and getting noisier ie more 'hiss'. A second question is with the V3 switched on to warm up, is the tubes lifespan being used up regardless of playing music or not? Cheers~ You will need a valve tester and you will have to check the transconductance / emissions. No way of checking with a multimeter or "by ear" but if they are starting to hiss then they are definitely knackered. If you send them to me I will test them in my tube imp The valve will be cooking whether or not music is playing, as long as it is glowing it is doing it's thing.... Before I had testers I would replace my valves every year as a matter of course. I would NEVER buy valves from somebody who sells them as "test good" and claim they are NOS even though they have clearly been used (print worn off the valves, socket "marks" on the pins etc.) Always best to go with brand new NOS.... ie: valves that have NEVER been powered up. You can buy a pair of "NOS" mullards which "test well" and they will sound crap compared to a brand new pair of Russian 6N23P-EB (for example).... these guys who say they test good never tell you what they are testing...... Plugging them in and seeing them glow is a "test" but means nothing. Anyways, I won't ramble on here but reckon it's time to replace your valves mate.... hissing and sonic deterioration is a sure fire sign that they are cream crackered. Mike.
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xerxes
Been here a while!
Posts: 1,115
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Post by xerxes on Mar 21, 2011 23:58:08 GMT
About 1960.
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Deleted
Deleted Member
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Post by Deleted on Mar 22, 2011 0:24:19 GMT
About 1960.
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rowuk
Been here a while!
Pain in the ass, ex-patriot yank living in the land of sauerkraut
Posts: 1,011
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Post by rowuk on May 21, 2011 20:09:28 GMT
Tubes will NEVER be out. Too many rock musicians out there that just happen to like microphony, hiss and hum.
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Post by ozelui on May 3, 2012 11:26:10 GMT
(extracted from www.rickresource.com/forum/viewtopic.php?f=19&t=162885)You can tell if tubes are going bad by the following: 1. Reduced power output. 2. Higher than normal distorion. 3. Fuzzy or cheezy sound which should be clean 4. Amps that blow fuses can have shorted output tubes. Visually inspecting tubes: Reject or test if: 1. The tube rattles when you shake it. 2. The silver getter inside has turned white, which means there is not vacuum left. 3. The getter is very brown or tan colored. Tubes tend to wear out if left on all the time, output tubes wear out super fast if biased to hot. New tubes generally have shorter lives than good NOS stuff. The biggest source of deterioration is heat, then vibration or a combination of both. For me, my biggest problem is tube rolling which does not allow them to rest on their sockets for a long while, LOL. I am also considering a Tube IMP for Small Tubes check.
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