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Cures for the Common Head (and Cab) Aches
What do you do when your amp starts making ungodly, non-musical sounds? Here are a few steps to help you isolate and solve a few common amplifier problems. First, plug straight into your amp. Just a guitar and cable – the more stuff you have in your chain adds more potential problems.
Fuses. Now you can easily blow a fuse due to a voltage spike. If you replace a fuse and it you keep experiencing issues, it could be something more serious, so take it to a good amp doctor. DO NOT replace the fuse with a different amperage fuse, or cram some kind of conductive material in there (paper clips, tin foil, etc) as you could damage your amp, or more importantly hurt or kill yourself!
To check if you have a bad speaker, here’s a simple test. Grab two wires, connect them to the terminals on a 9v battery, and then touch them to the terminals on the speaker. If you get any noise from the speaker, your speaker should be OK.
Guitar amps generally have two parts: the preamp, and the power amp. One quick check to see if it’s a preamp problem is to plug your guitar into the power amp section directly. This may also be called the effect return input on your amp. If you get a good signal using this method, it’s more than likely something related to the preamp section of your amp.
Tubes. Take a look at them while your amp is on, is one glowing a bit differently? One way to find a bad tube is take a guitar pick, and tap on the tube lightly while it’s on. If it’s bad, you’ll get a noise when you tap on it. It works for preamp and power amp tubes. If it’s a preamp tube, try swapping them around, taking the one in the first socket and swap it for the one from the last socket, and so forth. Not all of the tubes are being used for the same circuit in the same way, so swapping a tube that’s actually part of the preamp with one that’s being used for the reverb or tremolo, may work in a pinch to get rid of any nasty hum or noise.
Most modern amps have a three pronged plug – that bottom one is the ground. If you’re using an older amp with just two prongs, you’ll want to change it over to a grounded one. One easy way to try to reduce hum when using a non-grounded amp is to rotate the plug the opposite way in the outlet. It might help a bit. BUT if the PA system is plugged in on the same circuit, and you’re playing guitar and singing, it’s very likely that when you get close to a microphone YOU will become the ground, which can result from getting lightly zapped or seriously hurt if you touch or go near a microphone stand.
As always, take care when it comes to dealing with electronic or electrical issues. When in doubt, consult a professional for your own safety.