Can a tube change its specs due to blows or hits?

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RockNote
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Can a tube change its specs due to blows or hits?

Postby RockNote » Thu 01/26/17 8:45 am

I have recently received a box of new JJ 6V6 tubes from an online vendor. Unfortunately, the box containing the tubes has taken quite a beating during transit. I am concerned that the tubes may have become damaged from this rough handling without it being visible. I have no equipment for measuring the tubes.

I hesitated to open up the box until I had been in touch with the online vendor. When I called, they informed me that if the tubes appear to be okay, then they are okay. However, in an Internet guitar forum I have since learnt that this statement may be questionable. I am to use the tubes in my Cornford Carrera which came from the factory with a JJ 6V6 tube. This amp uses just a single output tube. (One at a time, at least, as it holds also an EL84 tube, which can be switched on when the 6V6 tube is not selected.) I wonder if this single-ended construction makes the amp more flexible/durable in case the new tube has changed its specs due to the rough handling it has received? At least, one does not need to be concerned with matching tubes.

According to Paul Cornford, who designed the amp with Martin Kidd, the amp does not need re-biasing when replacing the output tube with one of the same type and brand. Hence, I need to trust that the tube that I put in is okay in terms of the specs it is supposed to have.

Should I be concerned about using the tubes even though they look all right?
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Re: Can a tube change its specs due to blows or hits?

Postby JMPGuitars » Thu 01/26/17 9:11 am

I doubt specs would change, but it could become defective. A hard enough hit could crack the glass, and then it might look cloudy or white instead of clear.

Regarding the amp though, I would ask questions at our sister site www.sewatt.com. Using the same brand and tube type doesn't tell you anything accurate about how an amp is biased. This site doesn't deal with single-ended stuff at all, so I would ask at sewatt.com to be safe.
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