If there were one word to regard above all others when learning how to troubleshoot a guitar amp, it would have to be "carefully." A guitar amp is an intricate, electrical sound-emitting device composed of a head (which houses the power amp), controls and tubes (if the amp has them) and the speaker cabinet, which is composed of a housing for emitting audio from the speaker or speakers. Dings and rips in the outer casing do not necessarily mean the amp is not good. It is the sound, from the inside, that counts. There are two types of guitar amps: combo amps and separate head and combo amps; both of these work in the same way, because a combo guitar amp basically just includes the head and speaker cabinet in the same housing, and they cannot be separated. For the purposes of learning how to troubleshoot a guitar amp, the head portion and the speaker cabinet portion will be discussed separately so that the methods told can apply to either amp type.
- The first step requires diligently checking out the most basic part of the guitar amp: the electrical end. Inspect the cord to ensure it is in good shape and plugged into the amp properly. The amp should turn on within a minute, and should have a light or hum to indicate this; please note that tube amps require the tubes to be looked at, and any that are blackened need to be replaced. Tube guitar amps also need at least five to fifteen minutes of sitting in standby to warm up the tubes before playing a guitar through the amp, because the tubes only work when heated, and this prevents them from being strained.
- If the amp is electrically sound, the next step is to inspect the speaker or speakers. One of the most common points of damage to an amp is the speaker, as playing at full volume for a lengthy period often blows them out. A guitar amp should never be played at full volume! A blown-out or worn-out speaker will sound muffled, scratchy and be quiet in comparison to a clear, crisp and clean sounding loud speaker of any size. Check the cabinet itself to see if there are any discernable rips or tears in the speaker, and then inspect the tiny set of wires that go from the back of the speaker cone up to the head. There should be a solid connection between the wire and the back of the cone.
- With the vitals of the guitar amp administered to, the next step involves making sure the head of the guitar amp is fully functional. The head consists of all of the controls and the instrument inputs and outputs. Many guitar amps now contain some kind of chip to provide various sounds or sound qualities, and the first thing to check to see if the amp is working is the volume control knob. The volume should go up and down without any feedback, buzzing or scratchiness when plugged into your ax. Sometimes dust can negatively affect an amp and cause noises when turning the volume knob, and this needs to be repaired if this is the case. Next, check all of the other effects, like tremolo, or reverb, and play with the settings from full on turns of the knobs in either direction to see if each sound comes out cleanly and correctly. Lastly, be sure to plug into each input and output and try these all out; the output will hook a head or combo amp up to another speaker cabinet for more sound.