How To Diagnose Amplifier Tubes

Although, an amplifier aids in increasing the sound of your guitar or audio device, it tends to develop problems from time to time. The main problem that faces amplifiers is failure of the tubes to work. There are two types of tubes: power and preamp tubes.

Power tubes propel signals out of the amp's speaker while preamp tubes boost and shape the incoming signal. When the tubes have problem, there are inconsistencies in the sound coming out of the amp.

The good thing is that you can easily diagnose the tubes. To do it you only need to do the following:

Check the fuse

The first thing that you should do is to take a look at the fuse and see if it's blown. The fuse is usually located in the rear of the amplifier near the power cord. You should unscrew the fuse and check if there are burn marks. If there are burn marks, it's an indication that the fuse has blown.

When the fuse has blown, it's an indication that the tube is dead or its dying and as a result forces the amp to draw a lot of power from the wall that overworking the fuse.

Check the tube

You should take a look at the tube and see if it's broken. A broken tube usually has white, black, or silver powder spots on its interior. In rare cases you will find that the tube has burned out. The tube burns just like a light bulb. In such a case, it usually has burn marks all over it.

Turn on the amp

You should turn on the amp and listen to its sound. The tubes usually produce a dull sound. If you stay for five to ten minutes and then the sound goes away, it's an indication that the tubes are bad. If the tubes are completely dead, the sound will not go away.


If your tubes are bad, you should not replace just a single one; you have to replace all of them. The purpose of this is to ensure that power is balanced among all the tubes. This results to a longer life of the tubes.

You should be careful when replacing the fuse. As rule of thumb you should not attempt to replace a fuse with a stronger one. This is because this will result in permanent damage of the central power of your amp.