new tubes glow red hot?

[dinky kustom]

ok sorry for the noob question,i have replaced the tubes [pre/power]in my jcm 900 [50watt head] with electro harmonics 6l6c and 12ax7.when i turned it back on the power tubes instantly started to glow very red down the bottom and had a blue haze up top.if i hit a chord at volume they would ''flair''up and glow a lot more before fading back to there normal already glowing state.this freaked me out a bit so for the time being i have put the stock power tubes back in.now it has not been biased as i was told by persons at music shop it wouldnt need it?.if not is it normal for the power tubes to glow that much and have a blue haze?its fine with the stock tubes in?i guess it pays to do some home work first.

[AlexL]

Not sure about the blue haze, but typically, power tubes DO have to be biased.

Preamp tubes do NOT have to be biased.


- E.

[Cleveland Metal]

They use 6L6's in those heads there? The ones here are EL34s...

And when I used to run 900s ( I had a few 4100s), my tech, who was the famous Dr Z (yes, that Dr. Z) always had to change the resistors to get them to bias properly as the stock tubes were weird (cheap chinese), and they used a weird resistor value that would not allow the amp to be biased correctly with a tesla or svet that we'd use... He was always irritated at those amps...

[dinky kustom]

They use 6L6's in those heads there? The ones here are EL34s...

And when I used to run 900s ( I had a few 4100s), my tech, who was the famous Dr Z (yes, that Dr. Z) always had to change the resistors to get them to bias properly as the stock tubes were weird (cheap chinese), and they used a weird resistor value that would not allow the amp to be biased correctly with a tesla or svet that we'd use... He was always irritated at those amps...

yea no el34s in jcm 900 after a period in time so most that came to aust had 5881/6l6 in them,but is it normal for them to glow what i would call excessivly red down the bottom?i have only ever seen the tubes that came in it glow,and they dont glow that much.i see a trim pot in there that i think is for the biasing but i know nothing about it.could i turn this one way or the other to see if they glow more or less or just leave it .its about a 3 hour trip to get a tech to do it and i dont go that way very often but i dont want to kill these new tubes in a matter of days either.?i can take pics if that may help between the two types and there glow?

[Cleveland Metal]

I'm thinking excessively glowing red is not so great man. Some red at the base is sorta typical, but if the plates are glowing red, I believe it would be out of bias a bit too much. That could kill the tube pretty quickly.

As I mentioned, when I owned them, those amps didnt have a lot of bias variability. Just to be safe, and not being able to see it myself, I'd recommend getting someone to look at it sorry to say.

[Spivonious]

Regardless of the glow amount, a blue haze is very atypical of tubes. I'd get the amp biased. You can do it yourself with a device to measure amps, but there are major currents running through the amp that could easily kill you, so I'd take it to a pro if you don't know what you're doing.

[yabba]

some blue haze is normal, IME (it varies quite a bit, and isn't really cause for concern), the red sounds bad though - they're probably biased way to hot right now and will burn out quick if you don't get them biased

[CharvelRocker]

I HAD THAT PROBLEM WITH A KRANK HEAD I HAD....THEN IT MELTED, THANK GOD THEY WERE HERE IN TEMPE AZ


KRANKENSTEIN SHOULD COME WITH A FREE FIRE EXTINGUISHER

[dinky kustom]

thanks for the info guys.i know next to nothing about tube amps ,just how to get a tone i like.looks like i have to make a trip so i can get it sorted .