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Post subject: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 9:13 am
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Hi there,

My Blues Jr. seems to be making some crackle and pop sounds when I get to louder volumes. It is fairly new, I have had it for about 2 years. This is my first tube amp, so I am still not to sure what repair and maintenance is involved.

I thought at first that it was maybe a blown speaker. I've browsed the forums, and it doesn't seem as though anyone else has had that issue. I am wondering it it is a tube issue?

I took the back off and observed while I played. It seems as though the V5 tube gets a little blue stuff going on inside. I'm wondering if it means that it is near the end of its life? I am not sure when tubes need replacing?

Thanks!
Kyle


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 9:25 am
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When they crackle and glow blue, it's probably time for a new pair of power tubes.


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 3:37 pm
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Maybe, but the blue glow could be normal. Some output tubes have the blue glow, some do not. You could even have the blue glow in only one of a pair of output tubes, sometimes meaning that the one with the blue glow is using more current than the other.

Crackling and popping could be from tubes, likely preamp or PI, but could also be from loose tube sockets.

http://billmaudio.com/wp/?page_id=171

Examples of normal blue glow:
Image
Image

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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 8:17 pm
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Nice pics.
I've seen a few glowing too. Seemed like playing with fire. The steel guitar player from the Texas Playboys had a Fender Twin BF that would flash the power tubes every time I hit the standby sw.
Replaced the tubes and it did the same thing. Put the old ones back in and he took it to Texas. Never did figure out why it did that.
It was my understanding that 500 volts was about minumum for ionization. Does it happen lower?

I guess I should have said," If it's blue and flashing like it's arcing, you probably need new power tubes."


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 8:33 pm
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Yes, arcing is not good. The top pic is an Egnater with a pair of 6L6, around 430 VDC on the Plates, and the lower pic is a HRDlx with a pair of 6V6, around 470 VDC on the Plates. Normally, with 6L6, the HRDlx has about 430 VDC on the Plates. I can get more or less blue by adjusting the bias higher or lower.

It is my understanding that the blue glow is due to some gases left in the tubes after flashing the getter. I have no idea whether or not the ones that glow blue will last as long as the ones that don't glow. So far, I haven't lost any that have the blue glow.

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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Sat Mar 21, 2015 8:39 pm
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This is a Carvin X100B with a quad of 6L6, with around 450 VDC on the Plates, and they only have a slight blue glow. For any tubes that do have the blue glow, it will not be there until the high voltage is applied, switching the standby switch to play. You might see the glow surge a bit at first, but this isn't arcing.
Image

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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Mon Mar 23, 2015 7:24 am
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shimmilou wrote:
Examples of normal blue glow:
Image
Image



Lazy blue or purple glow in output tubes is ok. Just interaction of electrons and the glass envelope or contaminates from manufacturing process burning off. Some tubes are noted for more of this glow that others. Like those tubes made in China.

Gassy tube glow is another matter. Usually, stronger & brighter. Good site describing both types:

http://www.jacmusic.com/techcorner/ARTI ... ueglow.htm


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Mon Mar 23, 2015 8:38 am
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I seem to notice that the blue colour happens when the crack sound is happening. Should I try replacing the tube anyway? If it is a loose socket, how would I fix that? Is that something I can do myself, or should I bring it in to a shop?


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Mon Mar 23, 2015 11:45 am
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Blue flashing and crackling at the same time means the power tubes need to be replaced. A loose socket won't do that.


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Post subject: Re: Blues Jr III - Crackle Issues
Posted: Tue Mar 24, 2015 9:23 am
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Blue glow can be normal in some tubes, you could try re seating the tubes and if you have some cleaner like DEOXIT spray the pins of the tubes and insert them in out a couple of times to help clean the pin contacts.


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