Common Amplifier Malfunctions: The amp smells like it's burning.

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?