[sproul07]

I have an '85 Marshall JCM 800 100w head and I am running EH 6550's in it, which I noticed are glowing blue. I have heard that when a tube is glowing blue, they are running too hot. Is this a problem for my amp?

 

[J S Moore]

Have you changed tubes lately? My JCM800 was biased way too high for the tubes that were in it originally. I think that is a standard though for Marshall to run the tubes hot.

 

[nonreverb]

What you're seeing is gas in the tube glowing...not an uncommon occurence...however if the plates (the big grey areas) are glowing orange like the embers in a fire then you have a bias problem

 

[Geek]

Hi,

Some informative links on the topic:

http://members.aol.com/larrysb/blue_glow.html
http://www.jacmusic.com/html/articles/blueglow/blueglow.htm

Cheers!

 

[nonreverb]

Good article Gregg :smile:

 

[J S Moore]

Excellent articles. I learn something new every day.