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I have some of the early 1940s radios. Mine are bakelite, but the screws on the bottom connect directly to the chassis which is live. Also, if you loose a knob, you are in trouble. A very dangerous design.
By the mid 1940(just after WWII, the power was coupled to the chassis via a 240k resistor or so and a capacitor. This is somewhat safer unless the capacitor shorts.
I also have 1953 model Hoffman TVs with live chassis. The Tubes are on a filament transformer, but the DC supply grounded on the chassis. Hoffman used a full length back and a paper cover behind the control door as well as non-conductive shaft on the front controls to protect the user. I do not know why a power transformer was used instead-I do not think the cost savings was that great.
Another example of what I think is a stupid way to design a set is a 1950 GE series string set that I have. They used the radio trick of wiring all the power supply grounds together and then coupling it to the chass via a resistor/capacitor network. Considering the labor used in tieing all the necessary components for a TV to the common internal ground, I think this design did not save any money over a power transformer.
I have two isolation transformers and always use them when repairing radios/tvs.
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