Smoke coming from transformer means........anyone?

Found an old tube rcv. turned it on and it started to smoke. I noiced the transformer was extremely warm. Will I cause any more damage turning it on? Shiould I replaced the transformer or junk it? Anyone able to help me?
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Yes, a Variac is a needed for vintage gear that has been out of service for awhile and/or recapping a piece. I am in the market for good used one right now. As Clueless mentions the caps can hold high amperage charges for long periods of time and you need to learn how to drain them properly if doing the work yourself. I have been shocked through one hand, on through the chest and out the other hand by equipment that has been powered down for weeks. These were "not" Martha Stewart moments, take care and caution.
The Variac method doesn't work so well if the unit has a tube rectifier. The tube rectifier won't really conduct until the filament voltage gets close to specification. This point will be somewhere around 75-80 volts AC input. At this point you put about 60% of the B+ voltage on the caps. Better than full voltage, though.
Wasn't that a Deep Purple song from the '70's..."Smoke on the Transformer"? Happy Tunes!