In Part I of our guide on fixing hum, we listed some easy fixes. In Part II, we’ll go into further detail on techniques that require some prior electronics experience to execute. It’s worth checking out Part I first, because it listed some simple, non-invasive things that you should always be tried before diving into the amplifier’s circuitry. For the purposes of this article, we’ll assume that you already tried everything in Part I. This includes:

Before we start, a disclaimer: hum should be addressed on a case-by-case basis, because every vintage amp is special and degrades in its own way. What cures one amp may not work for another. That said, reading this guide should give you a good starting point on how to address your own hum problems. This guide is pretty basic and going to assume that the only piece of test equipment that you have is a multimeter.