Capacitor’s Swan Song

Capacitor’s Swan Song

This week’s post is a bridge between two passions of me. And what better way to bridge electronics and retro computing than a tool? And I also like tools, so it is cool. Before you turn on a 30+ year old electronic equipment – which is what you really aim for when you caught the retro-computing virus –, you should always open up the beast and check some of its components. The minimum should be capacitors and power supplies. The formers have the bad taste to age badly and often blows up fairly quickly, releasing the magic smoke – which smell pretty nasty by the way. So inelegant. The already blown-up and leaky caps can be easily spotted. But for all the not so obvious cases, I use an ESR meter. ESR stands for Equivalent Series Resistance. Indeed, real capacitors (not those ideal unicorns you find in frolicking in text books) are also resistive, and as they take their beating during their lifetime (abuse, age, temperature cycling), their start dissipating power. ESR is more complex than just considering it as being the total internal résistance of the capacitor, but for now that will suffice. Especially since electrolytic capacitors are what we are looking for in general with antique electronics. As their age, the dielectric solution/gel inside them tend to dry out. With an ESR meter, you can get both, the ESR and the capacitance. The Atlas ESR+ I have (or ESR70 by Peak) is a bit pricy, but it is extremely handy. Among the cool features – in addition of its main purpose of course –, it discharges the caps, can be used in-circuit (not powered), and has a buzzer for audio feedback. It handles ESR measurements from 0 to 40 ohms with a 0.01-ohm resolution, and capacitance from 1 to 22,000 microfarads. You just have to hook the suspicious cap’s leads of the instrument, and in few seconds you get your readings! Simply replace the faulty ones. No more Swan Song of the Capacitor for you. That is true of course if you don’t skip this step. I have to confess that I blew my fair share of caps by being impatient 😉