Lethal Hazards of AC-DC Radios and Televisions - John Dunn, Consultant, Ambertec, P.E., P.C.

Remember the good old days before the CK722? Remember when your table model AM radio cast a warm, friendly glow on the wall from the filaments of its vacuum tubes? Remember the comforting warmth of the radio's cabinet? Remember how that thing had the capability of killing you?  

 
It's hard for some younger folks to believe, but these things could be lethal if you happened to come into simultaneous contact with such a radio's chassis, or in some cases the chassis mounting screws or control knob shafts and the nearest radiator.

There were television sets made this way too and they were just as dangerous, especially the AC-DC televisions that used metal cases.

If you ever happen to come across one of these oldies, BE CAREFUL. As Captain Kirk said to Ensign Chekov in one episode, "At close range, these things can be as deadly as a phaser."

 

 

Comments

[Carl Schwab]

,
Starting in 1939 I started to work part time for the Richter Appliances, a dealer in a small town near where my parents farm was located. I worked there all through WW2 until I graduated high school. So I saw plenty of the AC-DC tabletop radios. When on the test bench I rigged a 4W test bulb with a clip lead that I connected to the radio chassis. If the light lit I reversed the plug. This meant that the chassis was connected to the AC neutral.

I was told that the designers had to get rid of the power transformer because of cost. I recall that I saw lot of Philco table tops (circuit nearly identical to what you show) and a whole bunch of Arvin and Crosley that had 3 and 4 tubes only. I recall that the Crosleys were $5.95 and the Arvin was $6.95--------the circuit you showed in the Philco line were $19.95 BTW Ted Richter who owned the store had a complete set of Riders Manuals that each year added a volume with the past years latest radio schematics.

[Kim]

Why do you think the electric chair is so effective? There is danger involved if not used or shielded properly ;)

[Mark Nelson]

The AC/DC radio chassis was introduced in the very early 1930s (when 110 VDC mains were still in use in NYC and other places with trolley and subway systems) as a cost- and weight-saving measure ("midget" radios were the rage then). Most cabinets and knobs were non-conducting, which helped mitigate the danger some, though metal cabinet radios were available too. As you said, many tube TVs also were transformerless, especially portables. Pretty much the entire run of tube-type home electronics (1930s to 1970s) had plenty of hot-chassis designs. How many people electrocuted themselves with their radios would be interesting to know. It wasn't considered enough of a problem that they were banned.

[Cor van de Water]

I would expect the line switch in the *phase* lead, not in the neutral lead as shown above. With that switch position, nothing is live that can be touched, whether on or off. Naturally, it needs some attention to plug (and outlet!) polarity.