Tube question... Tube is changing colors on only 1 side??

[tele_jas]

Hi, I noticed the other day that in my Rectoverb that the tubes that came in the amp (Groove Tubes 6L6's) are changing colors to a silverish/black color but only on one side or area of the tube about the size of a quarter? What does that mean? I'ts on both tubes in the same spot and the same size - maybe I'm just a dumbass and they are supposed to be like this or came like this??? If I had a way to post a pic I would but I don't have any webspace (that isn't Flash) to do that with (and not quite sure how to do so).

Needless to say, I didn't play with them this weekend, I borrowed a couple tubes from my Triple to be on the safe side but if the GT's are OK, then I'll go ahead and put those back in and save a few $$ until they do start to get week.

Is this a normal thing?

Thanks...

 

[Ken j]

Are you refering to the spot were the getter (sp?) is? This is the part of the tube that burns off any remaining oxygen when it is fired up for the first time. It usually leaves a silver spot on the inside of the glass. Depending on the tube manufacturer it can be in a number of different locations in the tube.