If you do not use any type of electronic gear for an extended period of time, powering up with a variac is never a bad idea. This is especially true if the devices are old and / or exposed to very high voltage levels ( like tubes ). So long as the gear is getting a good workout on a somewhat regular basis, it is not really a big deal. However, the older the gear & the less it is used, the greater the potential for damage.
As with most electronics, high heat levels are a major problem for capacitors. Items should not be stored in an area that is exposed to high temperatures ( like an attic ) or someplace that has a heat duct blowing directly on the items. Newer capacitors can deal with this a little better than older caps, but none of them really "like" this kind of treatment.
If you have other tubed gear and / or buy older used gear, a variac is kind of a handy thing to have. Just make sure that you fuse the input to the variac ( from the AC wall outlet ) and the output which feeds the gear being powered up. It is quite possible to smoke a variac when powering up gear that is not "healthy". Everything might be fine until you hit a certain voltage point and then "poof".... As you might guess, it's cheaper to blow a fuse than to smolder the variac. Sean
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