[TV MAN]

I'm gonna throw a monkey wrench in this line of thought. I believe it is a good idea to have BOTH a separate variac and isolation transformer. Why? You NEED the protection of the isolation transformer when working on a bare chassis. You need to be able to vary the voltage to bring up, test and watch with the variac. In the real world, a radio/tv or such is designed to work directly off the line. My point? When you want to test something, there ARE times when you NEED to connect it directly to the line, but still have the variability of the variac. On the ac/dc radio sets, the chassis is connected directly to one side of the ac line. Fine when it is plugged in correctly. If it is reversed, then the chassis becomes "hot", and can give you a pretty good shock. The variac connects directly to the ac line, one side is simply a short from your outlet to the variac outlet, the other side runs through the transformer. It works like a dimmer switch that are on ceiling lights. So, you get NO protection using only a variac. Besides, if the variac or isolation trans fails, you only need to replace one or the other. I think it is good plan to have both. My experience anyway.