I Have a Strange...

[radiotvnut]

I remember reading an article from an old radio / TV servicing magazine concerning the dangers of hot chassis radio & TV sets housed in metal cabinets. According to the article, part of the problem was failure of the service technician or DIY'er to place the insulating devices between the cabinet and the chassis when service was complete. The article also mentioned cases of electrocution from such sets. I've had several of those metal radios from the '40's and '50's. None of them had any sort of insulation between the chassis and cabinet. At best, the chassis was connected to one side of the line through a capacitor. I always install polarized cords on AC/DC sets that I service. Of course, it can still be dangerous if the outlet that it's plugged into is wired wrong. I've also run into a fair amount of early AC/DC radios with the "curtain burner" resistance line cord. Now, exposed hot chassis and resistance line cords would never fly with UL.

[Old1625]

Originally Posted by radiotvnut

I remember reading an article from an old radio / TV servicing magazine concerning the dangers of hot chassis radio & TV sets housed in metal cabinets. According to the article, part of the problem was failure of the service technician or DIY'er to place the insulating devices between the cabinet and the chassis when service was complete. The article also mentioned cases of electrocution from such sets. I've had several of those metal radios from the '40's and '50's. None of them had any sort of insulation between the chassis and cabinet. At best, the chassis was connected to one side of the line through a capacitor. I always install polarized cords on AC/DC sets that I service. Of course, it can still be dangerous if the outlet that it's plugged into is wired wrong. I've also run into a fair amount of early AC/DC radios with the "curtain burner" resistance line cord. Now, exposed hot chassis and resistance line cords would never fly with UL.

That resistance cord idea was a cutie, but I never liked it. The term you use is very appropriate.

The other cute trick was to put the on-off switch on the ground side of the line, making any metal part of the set dangerous to touch in the off or on position, depending on how it was plugged into the outlet. When I was a wee tot we had an old Zenith table radio that was missing both volume and tuning knobs. Where we lived was in a house in FL with a concrete slab/tile floor. My older sisters (usually barefoot around the house) used to either stand on a pillow when changing stations, or would use a playing card in the slot of the splined shaft.

[electroking]

This past November, I was near Trois-Rivieres, and I spent an evening
playing with a small radio I have had for years. IIRC, it doesn't even have
a nameplate, although I don't believe it is a homebrew. This is a 4-tube
TRF design with 78 RF amp, 6C6 infinite impedance detector, 41 audio
output and 80 rectifier. I tested the tubes (for the first time in about
30 years of ownership) and found all to be good except the 6C6 that barely
wiggled the needle of my Heathkit TT-1. After a NOS replacement (wartime
U.S. Navy surplus) was installed, I fired up the radio.

With an antenna consisting of the telephone with its 25-foot cord,
I managed to pull in CBC in Moncton with good volume for about an hour, a station about 400 miles away.

You can have fun with a simple AM radio!

[Jeffhs]

I never cared much (or at all), either, for the "curtain burner" resistance line cords because they got so hot in operation. My grandmother had a 1936 Silvertone AC/DC radio that had a resistance line cord; for years it was in her summer cottage, left unplugged, of course, when she wasn't there or in the off-season. The cottage had curtains on the windows; I hate to think what would have happened had that resistance cord come in contact with them.

In the late '60s-early '70s, I had a 1955 transformerless Emerson portable TV in a metal case (which also wound up in my grandmother's cottage when I eventually got a new set). The TV worked well enough, but the metal case could well have posed a shock hazard (thank goodness mine never did; the AC switch was bad and had been jumpered, so the TV was always unplugged when not in use anyway). I don't know for the life of me why some TV manufacturers (even reputable, long-standing manufacturers such as Zenith) even put some models of their sets in metal cabinets in the first place when they knew (at least they were supposed to know) that transformerless televisions in metal cabinets were disasters waiting to happen under the right (or wrong[!]) circumstances. Deteriorated or missing insulation barriers (some do-it-yourselfers and even some technicians who should have known better sometimes left insulation schemes such as barriers off the cabinets of transformerless TVs and AC/DC radios, thinking they weren't needed--after all, the set worked without them), failed blocking capacitors, accidental contact with the chassis--anything could cause these sets eventually to become death traps. I also had a 1959 Zenith metal-cabinet TV which had a power transformer, but that set never was a concern to me as far as shock hazards went because the transformer effectively isolated the chassis from the cabinet.

There is a way, however, a transformer-powered TV in a metal cabinet can become a death trap, aside from the high voltage on the CRT or a defective power cord: if the power transformer develops a short that, for whatever reason, does not trip the house circuit breakers. This will happen because the core of the power transformer is usually grounded; if the windings short to it, either the TV's own line fuse or the house fuses/breakers will open. If they do not open and kill the circuit, the entire case of the television will be charged with the full line voltage. What would happen to the rest of the house is a different story.