blue glow

[tonka]

I know that 6l6s useully glow blue is there a problem if one of them doesnt

[Albert Kreuzer]

No.
The blue glow is just a side-effect, not a necessity.
Some tubes do it, some don't.

[Enzo]

Well, depends on what you mean.

SOme 6L6s glow and some don;t, it is all a matter of how hard the vacuum is in the bulb.

But in general if I have a row of four same type tube, in particular a matched set and all of them have the glow but one, it is often a good indication that tube is not conducting. When I buy a quad of Sovtek, or JJ or whatever tubes, I have a reasonable expectation they are all from the same batch. And so I'd also expect all of them to probably have about the same level of free gas molecules floating around inside. From electrons flying around inside, it is the free gas molecules that get ionized and cause the glow.

So if the one tube has an open screen resistor - maybe because the tube just replaced had shorted out - it won;t glow like its brothers.

Now it may just be an odd tube, but when one looks different, it really should be checked out.

[tonka]

Yea i need to get it checked out .They are a set of 4 tubes that use to all glow the same. i swiched them all around and its not the tubes .Its thetube on the far left that dosent glow blue no matter which tube i plug in it.