[Jeffhs]

The cord was cut off on this TV set for a good reason--there are one or more short circuits or other very major problems somewhere in the chassis.

It is never a good idea to plug a very old TV or radio, stereo console, etc. into AC power and turn it on before replacing, at very least, the electrolytic filter capacitors in the power supply, the first step in a procedure followed in television/radio restoration known as "recapping". If the TV you found has a power transformer, shorted filter capacitors can damage or destroy it and/or the low-voltage rectifier tube if the power supply is not fused, or if the fuse has been bypassed or replaced with one larger than the original. If you see white smoke coming from "the power supply box", which I am guessing means the high voltage cage, your TV's flyback transformer may be shorted and will have to be replaced, although there is a fuse in the high-voltage cage that is supposed to protect the flyback in the event of major shorts, say in the horizontal-output tube.

Any number of components in the set could have burned out or been destroyed when it started smoking. If you pulled the plug as soon as you saw the smoke, there may not be too much damage, but I wouldn't count on it; the longer the set was on the greater the damage will be. If you saw clouds of white smoke coming from what you refer to as the PS box (again, I'm guessing--I don't know if you mean the HV cage or the area in which the TV's power transformer, if used, is located), there is a very major short in the set; needless to say, this TV must not be used again until it is recapped, at least in the low-voltage power supply. Again, damage of varying degrees may have occurred in other parts of the set as well. You are very fortunate that the set did not catch fire.