What does it mean when one tube glows blue?

[boogiemon]

i've tried swapping the two power tubes & the pi tube but the tube on the outside always glows blue the inside one does not.

 

[Horizon6505]

I could mean that the voltage is not properly reaching the tube. I'm not too sure.

 

[sparklesmcgraw]

When working the tubes should always glow blue.

If running in Simul class all 4 should glow, in Class A the two outer ones only should glow.

If the tube that isnt glowing is selected then it may be defective. How old are they and what kind are you using?

 

[boogiemon]

It's a sixty-watter: only two power tubes. The position on the right (looking from the back) glows blue which I know is ok, but shouldn't both positions do this? I've tried swapping tubes but it's always the one on the right that glows blue.

When working the tubes should always glow blue.

If running in Simul class all 4 should glow, in Class A the two outer ones only should glow.

If the tube that isnt glowing is selected then it may be defective. How old are they and what kind are you using?

 

[SonicProvocateur]

My 60 watter was like this with my EH tubes, but not my STR-425's. It has to do with the tubes themselves and voltage applied. I talked to phyrexia about it, and he said it was normal and that it was probably that the EHs weren't perfectly matched....

Yet again, that tube later popped and burned a screen grid resistor. Maybe early signs of a leaky resistor? I know my amp needed a slight rebias, so maybe its time for some dialing in on yours...

 

[boogiemon]

Thanks for the data point. i've tried a couple different pairs of power tubes w/no change: t he one on the right glows blue, the one on the left doesn't. i've also changed the phase inverter tube w/no effect. i wouldn't care except that this boogie doesn't seem to "boogie" like it should. Even for 60 watt's it seems like it has no headroom. Down low everything is good but turned up in a band setting it's kinda under-whelming.

My 60 watter was like this with my EH tubes, but not my STR-425's. It has to do with the tubes themselves and voltage applied. I talked to phyrexia about it, and he said it was normal and that it was probably that the EHs weren't perfectly matched....

Yet again, that tube later popped and burned a screen grid resistor. Maybe early signs of a leaky resistor? I know my amp needed a slight rebias, so maybe its time for some dialing in on yours...

 

[SonicProvocateur]

Thanks for the data point. i've tried a couple different pairs of power tubes w/no change: t he one on the right glows blue, the one on the left doesn't. i've also changed the phase inverter tube w/no effect. i wouldn't care except that this boogie doesn't seem to "boogie" like it should. Even for 60 watt's it seems like it has no headroom. Down low everything is good but turned up in a band setting it's kinda under-whelming.

Yeah...im thinking smoke and popped tubes is the next thing to happen...

Might wanna upgrade screen grid resistors (from 1 watt to 3) and rebias.

 

[boogiemon]

re-bias? i thought boogies are fixed-bias...

Thanks for the data point. i've tried a couple different pairs of power tubes w/no change: t he one on the right glows blue, the one on the left doesn't. i've also changed the phase inverter tube w/no effect. i wouldn't care except that this boogie doesn't seem to "boogie" like it should. Even for 60 watt's it seems like it has no headroom. Down low everything is good but turned up in a band setting it's kinda under-whelming.

Yeah...im thinking smoke and popped tubes is the next thing to happen...

Might wanna upgrade screen grid resistors (from 1 watt to 3) and rebias.

 

[Horizon6505]

just asking, but what amp is it?

 

[boogiemon]

just asking, but what amp is it?

An early mark III

 

[Horizon6505]

just asking, but what amp is it?

An early mark III

Hmm. I dunno then. Have you called mesa?

 

[boogiemon]

I think I'll just drop it off at the factory tomorrow. It's only about an hour from me. I'll post the outcome back to this thread once I get the official word. Thnx for all the input.

just asking, but what amp is it?

An early mark III

Hmm. I dunno then. Have you called mesa?

 

[thunda1216]

i've tried swapping the two power tubes & the pi tube but the tube on the outside always glows blue the inside one does not.

could be worse: one could be glowing red!

 

[SonicProvocateur]

re-bias? i thought boogies are fixed-bias...

They are fixed bias, but you they can be adjusted slightly (or so I believed, someone correct me if i'm wrong).

 

[elvis]

Could be a cold solder joint on the bias, or bad socket contact. Or output transformer (I hope not!).

 

[boogiemon]

Well I hope the factory can figure it out. At this point the clean channel sounds like crap if it's loud enough to drown out the fan noise. :^(


:x

Could be a cold solder joint on the bias, or bad socket contact. Or output transformer (I hope not!).

 

[wizard333]

Blue means the purity of the vacuum isnt great as it could be and there is oxygen in the tube.

As long as it sounds ok, nothing to worry about.

 

[kekam35]

Blue means the purity of the vacuum isnt great as it could be and there is oxygen in the tube.

As long as it sounds ok, nothing to worry about.

+ 1

 

[MesaDCLP]

+2
It's oxygen in the tube. It doesn't hurt anything.

 

[boogiemon]

...Just got a call from the factory and the answer in this case is that the left tube socket had a loose/broken ground connection. I'll get it back tomorrow or next week and post again on what sonic difference there is if any.

It's a sixty-watter: only two power tubes. The position on the right (looking from the back) glows blue which I know is ok, but shouldn't both positions do this? I've tried swapping tubes but it's always the one on the right that glows blue.

When working the tubes should always glow blue.

If running in Simul class all 4 should glow, in Class A the two outer ones only should glow.

If the tube that isnt glowing is selected then it may be defective. How old are they and what kind are you using?