Well, I have asked once in the past regarding new tubes in my JCM 800 50 watt amp. There were many responses but there seems to be no agreement. I was finally put in touch with a reputable Marshall certified Technician, and he told me... Obviously a degraded sound quality would be a hint but he would test if the tube had become microphonic, which means Sensitivity to vibrations causing noises and ringing. Tubes are especially prone to microphonics and will self-oscillate. He told me to turn on the amp and let it warm to operating temperature. Then, with the rear sheild removed (on my JCM Model) yours may vary, to lightly tap on the top of the warm tube, if you hear the tapping sound through the cabinet speakers, it is microphonic and are in need of change. His name is Barry and he owns a store called the Audio Clinic in Uncasville, CT. I hope this helps.
Rod
You are at GuitarMasterClass.net
Don't miss today's
free lick. Plus all our lessons are packed with
free content!
--------------------
Electric Guitars : Gibson Les Paul Standard "Raw Power", Fender American Deluxe HSS QMT Stratocaster
Acoustic Guitars : Ovation 1771 LX Balladeer
Effects : Digitech Jammer Looper, Digitech DF7 Distortion Factory, Boss DD-3 delay, Keeley Modded Boss DS-1, Keeley Modded TS-808 Tube Screamer, Keeley compressor, Dunlop CryBaby Wah.
Amps : 1982 Marshall JCM 800 2204 50 watt Head (all original unmodified Electronics, Complete cosmetic restoration) It is the "Tone of the Gods" 1982 Marshall 1960a JCM 800 4x12 Slant Cabinet
Rodnator How To Tell If You Need To Have Your Tubes Replaced Feb 20 2008, 07:10 PM
