blue glow on one channel

wicked1 · 27th April 2008, 01:19 AM

Hi,
One of the tubes in my amp has always had a blue glow. Today I finally decided to do some testing, and swapped tubes, and still, the right channel was the one glowing.
I even used a different type of tube, and same thing.

I checked the current and voltage on both channels, and they are exactly the same.

this is a 300b se amp.

What else could cause this if the voltage and current are the same?

thanks!

SY · 27th April 2008, 02:19 AM

http://www.jacmusic.com/html/article...w/blueglow.htm

wicked1 · 27th April 2008, 04:07 AM

Well I know it's not gassy, and it's nothing to worry about, but I haven't found anything that says why one channel does it. It's not dependent on the tube, but on the channel.

Thanks for the link. I hadn't seen that particular site. Lots of great glowing tube pictures!

m6tt · 27th April 2008, 04:32 AM

Have you tried replacing the coupling cap? It's a long shot, but I've seen weirder.

vax9000 · 27th April 2008, 05:36 AM

Would a high frequency oscillation cause the problem?

m6tt · 27th April 2008, 05:40 AM

I've seen weird loading cause blue glows otherwise unexplainable as well. Maybe back emf from a transformer?

Jeb-D. · 27th April 2008, 05:19 PM

It's normal for some tubes to glow, if it is on the inner glass surface. Although, that's weird that it's always on one channel even when switching tubes. I've seen oscillation cause blue glow between the plate and the cathode, but not on the glass surface.

Read this link.
http://members.aol.com/larrysb/blue_glow.html

Here is a picture of one of my amps that glow. Sorry for the size

kevinkr · 27th April 2008, 11:02 PM

Differences in the local magnetic fields around the output tubes? Just a thought..

Original Burnedfingers · 29th April 2008, 12:00 AM

New 6BG6GA's All 6BG6GA's I have are showing some blue glow.

They test and work normally. Besides being SY's favorite tube they just cannot be bad.

How about the way the tube is put together?

SY · 29th April 2008, 12:12 AM

Nice ST-70 there!

27th April 2008, 01:19 AM	#1
wicked1 diyAudio Member Join Date: Jan 2008	blue glow on one channel Hi, One of the tubes in my amp has always had a blue glow. Today I finally decided to do some testing, and swapped tubes, and still, the right channel was the one glowing. I even used a different type of tube, and same thing. I checked the current and voltage on both channels, and they are exactly the same. this is a 300b se amp. What else could cause this if the voltage and current are the same? thanks!

27th April 2008, 02:19 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	http://www.jacmusic.com/html/article...w/blueglow.htm __________________ If there's a sucker born every minute, where do the rest of them come from?

27th April 2008, 11:02 PM	#8
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Differences in the local magnetic fields around the output tubes? Just a thought.. __________________ "Extraordinary claims require extraordinary evidence." - Carl Sagan

29th April 2008, 12:12 AM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Nice ST-70 there! __________________ If there's a sucker born every minute, where do the rest of them come from?

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27th April 2008, 04:07 AM	#3
wicked1 diyAudio Member Join Date: Jan 2008	Well I know it's not gassy, and it's nothing to worry about, but I haven't found anything that says why one channel does it. It's not dependent on the tube, but on the channel. Thanks for the link. I hadn't seen that particular site. Lots of great glowing tube pictures!

27th April 2008, 04:32 AM	#4
m6tt diyAudio Member Join Date: Aug 2007	Have you tried replacing the coupling cap? It's a long shot, but I've seen weirder.

27th April 2008, 05:36 AM	#5
vax9000 diyAudio Member Join Date: May 2006 Location: Cleveland	Would a high frequency oscillation cause the problem?

27th April 2008, 05:40 AM	#6
m6tt diyAudio Member Join Date: Aug 2007	I've seen weird loading cause blue glows otherwise unexplainable as well. Maybe back emf from a transformer?

27th April 2008, 05:19 PM	#7
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	It's normal for some tubes to glow, if it is on the inner glass surface. Although, that's weird that it's always on one channel even when switching tubes. I've seen oscillation cause blue glow between the plate and the cathode, but not on the glass surface. Read this link. http://members.aol.com/larrysb/blue_glow.html Here is a picture of one of my amps that glow. Sorry for the size

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