guitar player's " dear Abby " letter

Courtesy of Leland Sklar over at totonetwork.com

http://www.totonetwork.com/node/218213

Dear Abby:

I think my wife is cheating on me. I am a working musician and, as you would expect, travel a lot. I have been noticing strange things happening when I get home. Her mobile phone rings and she steps outside to answer it or she says, "I'll call you back later." When I ask her who called she gets evasive. Sometimes she goes out with friends but comes home late, getting dropped off around the corner and walking the rest of the way.

I once picked up the extension while she was on the phone and she got very angry. A buddy of mine plays guitar in a band. He told me that my wife and some guy have been to his gigs. He wanted to borrow my guitar amp.

That's when I got the idea to find out for myself what was really happening.

I said "sure, you can use my amp but I want to hide behind it at the gig and see if she comes into the venue and who she comes in with." He agreed.

Saturday night came and I slipped behind my Marshall JCM800 half stack to get a good view. I could feel the heat coming off the back of the amp. It was at that moment, crouching down behind the amp, that I noticed that one of the tubes was not glowing as bright as the other 3.
Is this something I can fix myself, or do you think I need to take it to a qualified technician?

Thanks,

Very Concerned Musician