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 Post subject: Tube Failure
PostPosted: 04 Aug 2019, 21:32 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi Everyone, This topic could go in components but since it relates to the numerous amps I have posted I thought here might be better. Most folks know that one of the key factors in my designs is long tube life. I don't see any need to re-tube amps on a regular basis. In guitar amps OK as they work them harder, in hi-fi no. I figure the tubes in my amps will be going strong long after I'm pushing up flowers. So today I had my first tube failure. A 12SL7 in one of the original Oddblocks went soft today. As in zilch gain. I figure with all the amps I have here and the many hours on some (probably 5000 on that particular amp) one tube failure in 11 years is OK by me. It was after all a NOS JAN one from 1944. BTW, I was so confident that the tubes were OK it took an hour to isolate the problem.

Good listening
Bruce

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 Post subject: Re: Tube Failure
PostPosted: 05 Aug 2019, 12:13 
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Joined: 01 Jun 2013, 09:05
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Quote:
It was after all a NOS JAN one from 1944. BTW


What make was it?
Its quite difficult to replace things like that. It will be interesting to see how long the others last. NB its not a power tube.
11 years is good!
What life do you get out of Tube rectifiers?

Regards
M. Gregg

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 Post subject: Re: Tube Failure
PostPosted: 05 Aug 2019, 12:23 
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Hi, National Union under contract to Western Electric (1944 for the US Navy). I have several as we bought up many for use in the kit amps. Super sweet sounding. The Sylvanias under the same contract are quite similar. Both are probably getting a bit scarce now though. Everyone raves about the RCAs of that vintage. I have the clear tops, gray plates and black top ones and the NUs and Sylvanias are nicer. Anyone using 12SL7s should pass on the GEs that have no base. The new Sovteks are OK if you like a brighter sound.

I use only SS rectifiers, usually UF4007 or UF4005, but some MUR types too.

Good listening
Bruce

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 Post subject: Re: Tube Failure
PostPosted: 12 Aug 2019, 04:32 
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Joined: 20 Feb 2014, 10:35
Posts: 59
Location: NZ
gofar99 wrote:
Anyone using 12SL7s should pass on the GEs that have no base.


Slightly confused, do you mean wafer-base GE 12SL7 tubes aka ‘coin base’ are no good?
Or is that a typo & you mean musically they have no bass?


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 Post subject: Re: Tube Failure
PostPosted: 12 Aug 2019, 10:18 
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Hi, Actually a minimal base. See photo.

Good listening
Bruce
Attachment:
GE 12SL7.jpg


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