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Old 5th March 2012, 02:27 PM   #1
jeapel is offline jeapel  Canada
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Default no logo on tube

Hi
I m reading from a web tube seller

" Comes from bulk with no logo or marking."

Is it normal and good tubes or reject stock from company

Thanks
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Old 5th March 2012, 04:22 PM   #2
DF96 is offline DF96  England
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It could be OK. Valve manufacturers would make batches for others, including their competitors, to label themselves. What matters is what is inside the glass, not what is printed on the outside.
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Old 5th March 2012, 04:29 PM   #3
kevinkr is offline kevinkr  United States
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In a case such as this you need to be able to trust the seller. What do you know about them - if on eBay do they have excellent feedback or something rather less?

In your favor is cheap (below market pricing) and/or a generous return/replacement policy.
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Old 5th March 2012, 06:00 PM   #4
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Or you can ask for a nice photos of internal elements, like plates, getters, ... and than try to indentify ...
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Old 5th March 2012, 06:51 PM   #5
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How would you tell if this is a 12AX7, 12AT7 or 12AU7 from the outside (if it was a noval tube of roughly the right size)?

Fran
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Old 5th March 2012, 07:08 PM   #6
DF96 is offline DF96  England
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Not always easy. Most anode shapes were used for more than one type. The real experts may be able to tell, though.
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Old 5th March 2012, 07:41 PM   #7
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Quote:
Originally Posted by woodturner-fran View Post
How would you tell if this is a 12AX7, 12AT7 or 12AU7 from the outside
First by testing. Second by examining the grid structure if part of it was visible. Third (worst case) sacifice one and dissect it.
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Old 5th March 2012, 07:56 PM   #8
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Ok, I just wondered was there some magic to it (other than measuring)


Fran
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Old 6th March 2012, 12:42 AM   #9
jeapel is offline jeapel  Canada
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thanks for all your advices
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