The *proper* common practice is to connect such a TV to an isolation
    transformer before operating it with the back off.

Speaking of which, does anyone know of a source for decent sized (100-200W)
reasonably priced isolation transformers?  Since most of my haunts have low
voltage logic and stuff, I never seem to run into them...

(The actual application is a high-voltage DC power supply using a
variac-style autotransformer (which itself does not provide any isolation.)

Thanks
Bill W