Electric Shock From Radios....

[PRR]

....and also the super-cheap transformerless Kay and Kent guitar amplifiers.

A summary of how UL requirements changed 1930s-1950s. Radios were getting more risky, a shock test was devised.

Guitar amps are different in that a radio can be sealed in insulation (radio waves in, sound out) but a guitarist almost has to be holding on to the common of the amplifier. This essay does not get into those changes.

https://incompliancemag.com/article/electric-shock-from-radios-a-review/

[shooter]

Interesting read;
I liked this statement;
"You can tell when the body resistance breaks down — it occurs simultaneously with the onset of the sensation of electric shock"
I did not know that, shocks, I'm quite well qualified there 

[davidwpack]

Initial shocks from defibrillators typically don't effect the heart. Subsequent shocks have to be given to ultimately break the thoracic resistance barrier. Bigger people in ventricular fibrillation will require more shocks to break the resistance barrier before the heart can be successfully defibrillated.