There are two major reasons why an amp might smell like it’s burning:

1. The amplifier is covered in dust, which is in fact burning from the heat of the tubes

2. The amplifier is malfunctioning and a component is burning

If you have any doubt whether your amplifier is burning, you should turn it off and unplug it right away. However, you may be asking yourself, am I overreacting? Is it correct to be concerned about this burning smell? Or do old amps always smell this way?

If your tube (or solid state) amplifier is not “turning on,” the cause of this problem could be a blown line fuse. The line fuse, also referred to as a mains fuse, is the fuse that stands between the main AC power and your power transformer. In an otherwise functional amp, the main fuse can and will blow when there is a problem between the wall outlet and your power transformer (PT). A fuse can also blow when there is a short somewhere in the amp. In either case, the fuse is doing its job when it blows and is protecting the amp by stopping it from running when there is a problem present that could harm the amp’s circuit.