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The hot chassis design is mind-blowingly dangerous by contemporary standards. These things weren't designed to modern creepage distances either. I would worry

The hot chassis design is mind-blowingly dangerous by contemporary standards. These things weren't designed to modern creepage distances either. I would worry about creepage to controls on these things. THe article mentions screws potentially being hot as well as other shock hazards finger-accessible through vent hols so no joke be careful to unplug a radio before moving it or otherwise handling it in a way beyond turning it on and tuning it. All of these safety standards are written in blood. Even with the RC network referenced in the wikipedia article, you're looking at leakage to the chassis of 4.5 to 11.3 mA: https://incompliancemag.com/article/electric-shock-from-radios-a-review/ https://incompliancemag.com/article/electric-shock-from-radi...

Aloha 4y ago
The safety interlock cover was mandated at one point by law (or by the UL), because of this - because there are user replaceable components inside (tubes), they mandated a pressboard cover that contained the power lead, so you couldn't hook it to power while also having the case open.
- Manuel_D 4y ago
  I've modified and disassembled several of these radios. There's a second connection behind the cover. This will be disconnected as you remove the cover, but you can easily reconnect it afterwards. I've done so myself to probe the various components (I only manipulated it while the power was off, though).
Animats 4y ago
I was shocked by one as a kid. It was not fun.
aidenn0 4y ago
Even wiring the chassis to the neutral line with a polarized plug would be a bit archaic today, though it greatly improves things (assuming the power-switch isn't on the same line as the chassis, which on many of these radios it is !!)
- analog31 4y ago
  Early guitar amplifiers were expected to be used that way. There was a polarity switch, and you flipped it to the position where the neutral was "connected" to the chassis via a capacitor. This arrangement is now known as the "suicide cap." There's a general agreement among players, that having a tech install a proper grounded cord doesn't spoil the "vintage value" of an old amp. Example here: http://www.thevintagesound.com/ffg/schem/deluxe_5e3_schem.gif http://www.thevintagesound.com/ffg/schem/deluxe_5e3_schem.gi...
gumboza 4y ago
Yes they are terrible. Should be consigned to museums and never celebrated. My grandmother had a tube TV with a hot chassis. The Bakelite controls were on chassis connected metal shafts. The only protection you had from being killed was beeswax you had to rely on the TV repair guy to apply to the grub screw holes on the shafts.
mikewarot 4y ago
I avoid anything over 12 volts or 15 amps, but I wouldn't call this mind-blowingly dangerous. Working on Kilowatt amplifiers with 3KV at 1 amp ready to burn you to a crisp, that's dangerous. In Europe, with 220+ volt lines, I'd have a different opinion.
- wglb 4y ago
  110 is seriously dangerous enough.
- buescher 4y ago
  I think you misunderstand. "Mind-blowing" is not about the courage or skill it takes to work on them, and it's in relative terms. They didn't have contemporary safety standards back then, so I don't think the manufacturers were being completely feckless. All that had to be learned. But today, would you build something that puts one side of an unpolarized plug onto finger-accessible screws and then give it to a neighbor?
  - mikewarot 4y ago
    No, but I would gladly repair it for them and explain the danger, if it were a family heirloom. For example, I recently helped a friend get his grandfather's 1949 Airline Television working. There were some interesting aspects of that circuit. My late father had a mint condition Sunbeam Automatic Toaster he loved to show off. It has a hot chassis. --- Back in high school(1980), my chemistry teacher, Mr Tchalo had an old conductivity demonstration apparatus that was essentially an incandescent light bulb in series with two copper prongs that would dip into a beaker. After explaining how it worked, he would slowly pinch them together, then challenge us to do the same. I never tried it. As I said, anything more than 12 volts or 15 amperes, and I get scared. Mr Tchalo was from the old school of teaching, he had been brought back from retirement to fill out the staffing levels required for certification. He spoke with a heavy accent and had some seriously thick glasses, his eyes had been injured in a gas attack in his childhood in Macedonia during The Great War. He was one of my favorite teachers ever.

Aloha 4y ago

The safety interlock cover was mandated at one point by law (or by the UL), because of this - because there are user replaceable components inside (tubes), they mandated a pressboard cover that contained the power lead, so you couldn't hook it to power while also having the case open.

Manuel_D 4y ago
I've modified and disassembled several of these radios. There's a second connection behind the cover. This will be disconnected as you remove the cover, but you can easily reconnect it afterwards. I've done so myself to probe the various components (I only manipulated it while the power was off, though).

Animats 4y ago

I was shocked by one as a kid. It was not fun.

aidenn0 4y ago

Even wiring the chassis to the neutral line with a polarized plug would be a bit archaic today, though it greatly improves things (assuming the power-switch isn't on the same line as the chassis, which on many of these radios it is !!)

analog31 4y ago
Early guitar amplifiers were expected to be used that way. There was a polarity switch, and you flipped it to the position where the neutral was "connected" to the chassis via a capacitor. This arrangement is now known as the "suicide cap." There's a general agreement among players, that having a tech install a proper grounded cord doesn't spoil the "vintage value" of an old amp. Example here: http://www.thevintagesound.com/ffg/schem/deluxe_5e3_schem.gif http://www.thevintagesound.com/ffg/schem/deluxe_5e3_schem.gi...

gumboza 4y ago

Yes they are terrible. Should be consigned to museums and never celebrated. My grandmother had a tube TV with a hot chassis. The Bakelite controls were on chassis connected metal shafts. The only protection you had from being killed was beeswax you had to rely on the TV repair guy to apply to the grub screw holes on the shafts.

mikewarot 4y ago

I avoid anything over 12 volts or 15 amps, but I wouldn't call this mind-blowingly dangerous. Working on Kilowatt amplifiers with 3KV at 1 amp ready to burn you to a crisp, that's dangerous. In Europe, with 220+ volt lines, I'd have a different opinion.

wglb 4y ago
110 is seriously dangerous enough.
buescher 4y ago
I think you misunderstand. "Mind-blowing" is not about the courage or skill it takes to work on them, and it's in relative terms. They didn't have contemporary safety standards back then, so I don't think the manufacturers were being completely feckless. All that had to be learned. But today, would you build something that puts one side of an unpolarized plug onto finger-accessible screws and then give it to a neighbor?
- mikewarot 4y ago
  No, but I would gladly repair it for them and explain the danger, if it were a family heirloom. For example, I recently helped a friend get his grandfather's 1949 Airline Television working. There were some interesting aspects of that circuit. My late father had a mint condition Sunbeam Automatic Toaster he loved to show off. It has a hot chassis. --- Back in high school(1980), my chemistry teacher, Mr Tchalo had an old conductivity demonstration apparatus that was essentially an incandescent light bulb in series with two copper prongs that would dip into a beaker. After explaining how it worked, he would slowly pinch them together, then challenge us to do the same. I never tried it. As I said, anything more than 12 volts or 15 amperes, and I get scared. Mr Tchalo was from the old school of teaching, he had been brought back from retirement to fill out the staffing levels required for certification. He spoke with a heavy accent and had some seriously thick glasses, his eyes had been injured in a gas attack in his childhood in Macedonia during The Great War. He was one of my favorite teachers ever.