Assuming the TV is plugged into an isolation transformer (although I think there is already a small transformer onboard), then ground is not part of the secondary side. Yet, high voltage from flyback still wants to arc to earth (or just about anything), through human body as a medium.


At the high voltage and very low current involved here a lot of things that we consider isolation are adequate conducting paths.

You did not ask, but for experiencing an electrical shock a capacitive coupling can be enough: the capacitor formed by your body and the surrounding ground planes is charged, and this brief charge current is enough to cause a shock.

  • \$\begingroup\$ Also, if you pick up the flyback transformer's output before the diode/capacitor voltage multiplier, you don't get DC - you get an AC voltage of approx. 15.6 kHz that will cause a capacitively coupled current into any bigger conductor nearby. This can be done with old TVs that don't have a combined transformer and voltage doubler. Holding the tip of an isolated (!!!) screwdriver close to the top contact of a good old PY500A high voltage diode is a famous way for quickly checking if the flyback in a TV still works: You can pull beautiful arcs away from the tube's contact. \$\endgroup\$ – zebonaut Jan 5 '13 at 9:12
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    \$\begingroup\$ Upvoted for the info ! But your info is not complete from a viewpoint of somebody who don't know what is capacitive coupling and how it happens. Diagram would clear it more precisely. \$\endgroup\$ – Standard Sandun Jan 5 '13 at 16:01
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    \$\begingroup\$ That's just for the you did not ask part of the answer, so I don't feel guilty for not writing an essay on it. And I am (also) a teacher by profession, so I like to leave something to be explored by the 'student'. Once he/she knows a few terms (in this case for instance: capacitive coupling) google is more than willing to provide all the explanation you want and more. \$\endgroup\$ – Wouter van Ooijen Jan 5 '13 at 16:31

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