[Bob2]

Didn't notice till last night. This is a 274B from my WA6 amp.
Have limited experience with tubes so I'm not sure if this is normal.
This is inside the glass. Looks cracked but it is not.

[medium jim]

Doesn't look broken....

Jim

[SET Man]

Hey!

   Look like mark left from the mica spacer when they insert the inner structure  assembly to me 

   So, if the tube still work fine than no need to worry. If the glass is cracked and the vacuum is loss the getter/flasher will turn white.

Take care,
Buddy 

[medium jim]

Hey!

   Look like mark left from the mica spacer when they insert the inner structure  assembly to me 

   So, if the tube still work fine than no need to worry. If the glass is cracked and the vacuum is loss the flasher will turn white.

Take care,
Buddy 

Additionally, if the glass was cracked, the mixture of air and gas inside of the tube would result in the tube looking milky inside.

Jim

[FullRangeMan]

The getter works with heat, it will turn white if the tube is warm, if the tube is cold the getter may not processing the gas inside.

This is a chinese tube??

[Bob2]

Thanks everyone for the info.
This is a Chinese tube. Tube seems to function properly. Being new to tubes/valves I just wanted to be sure this wasn't a problem.

Bob.

[FullRangeMan]

After inspecting my chinese 300B I noted they dont had any track like your tube, but the mica also is this thin.

[Bob2]

FULLRANGEMAN,
Thanks for taking a look at your tubes. I appreciate the input!
Had the amp powered up last night for about 3 hours and no problems. No change in appearance..
If anything it's starting to sound pretty good....or maybe I'm just getting used to it! 

Thanks again everyone!

[medium jim]

FULLRANGEMAN,
Thanks for taking a look at your tubes. I appreciate the input!
Had the amp powered up last night for about 3 hours and no problems. No change in appearance..
If anything it's starting to sound pretty good....or maybe I'm just getting used to it! 

Thanks again everyone!

Tubes will sound better as they burn-in.

Jim

[FullRangeMan]

FULLRANGEMAN,
Thanks for taking a look at your tubes. I appreciate the input!
Had the amp powered up last night for about 3 hours and no problems. No change in appearance..
If anything it's starting to sound pretty good....or maybe I'm just getting used to it! 

Thanks again everyone!

Hi,
Seems this line mark is visible with the tube cold, by what I understand about mica it is a electrically inert material.
If it broken it my not create any problem to the getter, maybe only some mica fragments.
So avoid hit/knoch in this tube when you cleaning the glass dust.