I just purchased a Scott/Eico/Fisher/Etc tube component off Ebay; is it safe to plug in and turn on?
In short, No, most often this is asking for trouble. This is probably one of the most frequently asked questions of Hot Glass Audio. Most vintage pieces have been sitting unused for a prolonged period of time. During this time, some components, notably electrolytic capacitors, will have degraded. Applying full line voltage to a vintage piece that has remained untouched for years can cause costly damage, and in some instances, an explosion could result from a defective electrolytic capacitor. It is best to power up such equipment using a VARIAC (variable AC transformer) to prevent costly damage. By slowly increasing the applied line voltage, you will have a opportunity to observe the current draw, and look for signs of damage that would otherwise not be possible by applying full power. Hot Glass Audio actually encourages customers not to power their equipment up until it is rebuilt or repaired, this to be on the safe side. Yes, people have been lucky and happened upon the Ebay untouched
