Recapping Audio Equipment
At Austin Stereo, we only take on vintage amplifier and receiver service that includes replacement of all electrolytic capacitors in the power supply and amplifier stages. As most of these units are over 40 years old, doing less does not make economic sense. Symptoms included degraded performance in either channel or both, hum, sporadic noises, and eventually, failure to operate. In some cases, damage to other components that are not easily replaced may occur.
Electrolytic capacitors (“caps”) are electronic components that perform a critical function in amplifier and receiver circuits. The electrolytic compound decays over time. A typical receiver has on average, 40 to 50 separate electrolytic caps in the amp and power supply sections. Some of the largest amplifiers and receivers have over 100 individual capacitors.
Quoted directly from a manufacturer of electrolytic capacitors. “The aluminum electrolytic capacitor has a limited life span. This occurs because the electrolyte in the element eventually dissipates.”
In the image to the right, the electrolytic capacitors are the larger blue cylinders. In some cases, you can actually see physical evidence that the capacitor has failed. The fact is that most of the time there is no visual indication of degradation or failure at all.
In earlier electronics, primarity vacuum tube amplifiers, non polar capacitors are also replaced. This depends on the composition, as some types decay with age, while other types are known for long term reliability, and are of very high quality. In these cases, we leave those capacitors in place.
It is of course possible to isolate the failing capacitors in a circuit, but this is not only laborious, it is the beginning of a never ending loop of replacing one after the other when they are all 40 years old or older.
If you would like to know more, or just need help falling asleep at night, here is some data on electrolytic capacitor reliability.