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The Power Tubes in my Vibrolux have turned...


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Ah ok. Thanks Phil. Like I said, the amp runs fine. The blue glow might have always been there and I just never noticed.

Is it possible for tubes to suddenly get a blue glow?



Sometimes handling them (with bare hands) will make them glow blue. My mate used to do it on purpose because you could see them through the front of his head and he thought it looked cool. :facepalm:

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Ah ok. Thanks Phil. Like I said, the amp runs fine. The blue glow might have always been there and I just never noticed.

Is it possible for tubes to suddenly get a blue glow?

 

 

Power tubes glowing blue/purple usually result from the amp being turned on with out a load attached, ie your amp may have been used without speakers which is NOT a good thing to do.

 

I'm not sure but it might be able to be cause by an impedance mismatch as well (?).

 

It is also possible that you have a bad connection somewhere with your speaker cable/jacks or even somewhere in the output stage of the amp.

 

I'm no amp tech but I believe the blue/purple colour results from a build up of charge feeding back into the power stage of the amp then oxidising something within the tubes.

 

The strange colour in and of itself does not necessarily mean the tubes are bad, but operating an amp under these conditions can is very unhealthy for your gear and can result in some nasty issues.

 

I would strongly suggest getting it looked at by a tech before using it again just to be on the safe side - you never know what other components might be having issues and what consequences you get if you keep using it.

 

tl;dr - take it to a tech.

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Great Post ^^^^^

Thanks!

 

 

tbh that's all 2nd hand information so I may be somewhat full of {censored}.

 

I'd still play it safe and have someone take a peak.

 

 

Some google-ing has revealed that there are a few causes for blue glow. Some tube types are more blue than others.

 

What type of tubes are they?

 

Is it intense blue or just a tinge?

 

 

 

 

 

This thread needs Andreas...

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Dude... it's almost certainly fluorescence, and NOTHING to worry about. Seriously, if you feel it needs to be looked at, and the "blue tubes" is the ONLY "symptom" your amp has, take a video or picture and toss it up and I'll have a look. But from what you're describing, even without the pic, I'd be willing to bet there is nothing to worry about. :)

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I've never heard that plugging your amp in without a load causes the tubes to turn blue. :idk:

 

I DO know that plugging your amp in without a proper load can cause Very Bad Things to happen - like blown transformers, fried parts - tubes, resistors, etc. And it doesn't take long, so avoiding that scenario completely is HIGHLY recommended. IOW, don't try experimenting to see if you can get your tubes to glow blue by connecting the amp without a load - ALWAYS run your amp with the correct impedance load connected! :wave:

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I've never heard that plugging your amp in without a load causes the tubes to turn blue.
:idk:

I DO know that plugging your amp in without a proper load can cause Very Bad Things to happen - like blown transformers, fried parts - tubes, resistors, etc. And it doesn't take long, so avoiding that scenario completely is HIGHLY recommended. IOW, don't try experimenting to see if you can get your tubes to glow blue by connecting the amp without a load - ALWAYS run your amp with the correct impedance load connected!
:wave:



Absolutely.

But I'm pretty sure I'm not making it up.....reasonably sure. :p

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That's why SS amps rule, no load = no problem.
:thu:



You can get SS amps to overheat by running at an impedance that is too low for too long though (less than 2 ohms for some amps). But in my experience it doesn't seem to hurt anything, just trips some sort internal failsafe that stops it working for 15 mins or so.

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This thread needs Andreas...

At your service...

 

I'm with Phil - a light blue glow from the filaments (the thingamagooks inside the tube) is just fine, and if the amp works as normal (normal sound, and no change in the sound over time) it's all ok. It's different if the glow seems to come from the whole tube (glass and all), but as long as it comes from inside the tube, it's ok.

 

A bright red glow from the whole tube (glass and all) is bad - the tube is either on its way out, the heater voltage is wrong or the bias voltage is completely off. But in all those cases, you'll definitely hear it too.

 

Keep in mind that the colour of the glow will change with the viewing angle. In a Fender amp the tubes (6L6's in the Vibrolux) hang from the chassis, so when you lean over the back of the amp to check, you're looking right in between the filaments. If you view the tubes from the rear, at level height, the glow might look different.

 

/Andreas

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I heard that this indicates poor performance of the crystal lattice. Those loose electrons are the weak ones carrying inferior frequencies that can't pass through, and they'll contribute to a buildup of bad tone in your amp until everything sounds like ass.

Bottom line: you needs a Dumble.

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the ONLY glow you need to look out for IMO is "cherry spots" on the plates...

you'll know why they're called that when you see it :lol:

or you'll be able to tell when they're cooled off, there's a significant distinct darker circle on the centers of the plates

edit: / bobby d has ME doing the CAPS thing

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I heard that this indicates poor performance of the crystal lattice. Those loose electrons are the weak ones carrying inferior frequencies that can't pass through, and they'll contribute to a buildup of bad tone in your amp until everything sounds like ass.


Bottom line: you needs a Dumble.

 

 

dumble's bottom line is not something to be mocked, it's quite expansive

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