Another question about tube amps?

[gagelle]

Why do some sellers of tube gear say that because the unit has been sitting around for awhile it should be hooked up to a (I forget name but it gradually increases the voltage.) before using, ? I read an article about a component (I think it was an electrolytic cap. but I could be wrong.) that needs a gradual charge for a chemical reaction to take place. I know you tech guys know all about this.

And my other question is why does this appear to be an issue only with tube gear?

[tube fanatic]

Electrolytic capacitors have a finite life span which is based on many factors. Check out the following tutorial which explains how they work in relatively simple terms:

http://www.hans-egebo.dk/Tutorial/electrolytic_capacitors.htm

Applying a very slowly increasing voltage to electrolytics allows them to re-form (see article for details about this) which, in many cases, can restore useful life to an otherwise "bad" capacitor (if the caps are installed in equipment, it is often done with a variac, a variable transformer). This does not apply to just tube equipment. All electrolytics, regardless of operating voltage, are prone to spoilage and failure.

[NOSValves]

much depends on a combination of how old the gear is and how long it has sat idle. IMHO with older gear (more then 25 years or so) a variac is a waste of time unless one just wants to see if it will work before they sink bucks in rebuilding it. Gear that old the caps may live but they sure are not living comfortably. Using caps that old is a sure fire way to end up needing a transformer replacement in the end.