How is thebest way to use a variac when firing up an old tube radio?
This is the method I think is best. Bring up the variac slowly, over a period of about half an hour, until you reach about 40 volts. This will pre-heat the tube filaments or heaters. Then, slowly, over another half an hour, bring up the Variac to around 80 volts. This is the point where the average tube rectifier just begins to pass current. This will allow the power transformer windings (in a transformer-equipped set) to warm up a bit,driving out any accumulated moisture, and will “re-condition” the electrolytic filter caps, allowing the electrolyte to re-form on the foil. Leave the Variac at this point for several hours, but not unattended, of course. Then you can start inching it up bit by bit, say ten volts every fifteen minutes. When you reach about 95 volts the radio MAY start to function. Or,. it may begin to hum, which means you need new filter caps.As a rule, I ALWAYS replace filters, whether the radio works or not. Old filter caps ALWAYS fail, sooner or later. Keep on advanci
