no logo on tube

[jeapel]

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

[DF96]

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.

[kevinkr]

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.

[radiostar]

Or you can ask for a nice photos of internal elements, like plates, getters, ... and than try to indentify ...

[woodturner-fran]

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

[DF96]

Not always easy. Most anode shapes were used for more than one type. The real experts may be able to tell, though.

[HollowState]

Originally Posted by woodturner-fran

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.

[woodturner-fran]

Ok, I just wondered was there some magic to it (other than measuring)


Fran

[jeapel]

thanks for all your advices