What's a properly lit 6SN7 tube look like?

I just purchased an SET 300B amp here on the 'Gon, and after a bit of light cleaning of pins and sockets, etc; I fired it up.

All the tubes light up, but the single 6SN7 tube only lights at the top, while the 6BX7's light top and bottom. I get no sound out of the amp, with the exception of a very weak sound (music from the source) in the R/channel, with the preamp turned all the way up.

Any help would be greatly appreciated!

Make sure the tubes are all seated correctly, you might have to wiggle them a bit in their sockets until you're getting both channels. 6SN7s, I have three of them, may light up very faintly, and in a lighted room you can just barely see they're on.
My 6SN7s glow top and bottom.
That's exactly what I needed to hear, thank you Brownsfan! Got a new one on the way, hopefully, that will do it.

Best regards,
Hi Dan

What kind of 6SN7 tube are you having a problem with? Also do you think the tube got damaged when the amp was shipped to you and that is what cause the 6SN7 to only glow at the top? Where do you get your 6SN7 tubes from? I've bought from Jim McShane in the past and he is great to deal with.

A "properly" lit tube can still be faulty. You have to replace with a known working tube. Jallen
don't judge a bulb by its' color...only one way
Some 6SN7s are properly lit when you can only see something from the top. A lot depends on the particular brand and vintage!
Thanks for the responses. All tube are firmly seated in their sockets. (This is not my first tube amp, nor is it the only one I have currently).

The tube in question is a Russian Tung-Sol. Only the top glows faintly. I have purchased all new tubes for the amp, as I believe the tubes are the original ones that came with the amp. The new 6SN7 and 6BX7's are on their way from Andy Bowman at Vintage Tube Services.

The 6SN7 would be hard to tell from a new one, it looks perfect. I'm hoping this will solve the output problem, but now, I'm having my doubts.

I guess I'll just have wait and hope.

Thanks much, regards,