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Discussion Starter #1
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?
 

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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.
 

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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
 
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