You are right, koolkar. I do profess to be an electrical engineer.
From evidence that I have found on the web, it takes as little as 1 Joule of energy through the heart to send it into fibrillation. How much is a Joule of energy? It is the discharge of one 26.4 microfarad capacitor charged up to 275 volts. (E=C*V^2/2). Now, if the radio was powered up, or there were more than one capacitor, the energy delivered could be significantly higher. B+ supplies usually have over 100 microfarads of capacitance available. That makes about 3.8 joules, which is enough to burn you pretty good and jolt your heart pretty badly.
Yes, commercial defibrillators typically provide 200J+ of energy, but they provide that much to make sure they work the first time, and they also have to overcome the resistance of the skin. If you accidentally [censored] yourself or your hands are wet you can easily overcome the skin resistance and then the impedance of your body is very low.
While very unlikely it is possible to get killed by working on tube car radios. Sure, if you have it out on the bench and it has been shut off for a while the caps probably leak down enough to not be dangerous, but if you have the radio in the car and maybe turned on and your hands are wet or sweaty and you grab the wrong thing and your heart is a bit weak you could die. Please err on the side of safety!
