How to Test a Tube Amplifier
Seasoned and beginning guitar players alike prefer tube guitar amplifiers for their overall tone and warm sound. But there is a certain amount of work involved in repairing and maintaining your amp's tubes. Loud crackles, feedback and hum are obvious indicators of dying tubes, but there are other subtle hints that many inexperienced guitarists don't pick up on. Fortunately, there a few ways to troubleshoot your tubes to single out specific problems with your amp.
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Instructions
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Turn on your amp. Use a 1/4-inch speaker cable to connect the amp to your external speaker cabinet, if present. Grasp each tube, and gently wiggle each tube. If you hear a crackling or popping sound that means the tube is bad, or going bad. Turn off the amp, pull the tube out of its socket and reinsert the tube. Disconnecting and reconnecting a tube may improve its connectivity to the amp's circuit.
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Power on the amp, and flip on the standby switch on the amplifier. Scan each tube and examine the color it emits. Working tubes emit a reddish, orange glow. If your tube is emitting any other color, it may be an indication that your tubes are going bad.
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Turn off the standby switch. Gently tap each tube with a pencil or similar object. If your tube changes colors, makes a crackling sound or your amp starts feeding back your tube is starting to go bad. Replace the tube, accordingly.
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Turn off your amp. Remove all tubes from the amplifier. Examine each tube for black, burn marks or discoloration. Replace the tubes with burn marks.
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Tips & Warnings
Always use extra caution when handling tubes. Dropping or mishandling your amp's tubes will break the components inside the tube.
References
- Photo Credit Amplifier image by Mladenov from Fotolia.com
