TVs with hot chassis - where signal ground is actually line connected and
at some intermediate (and dangerous) voltage - will have an isolation block
in between the tuner and antenna/cable connections. TVs with isolated power
supplies may have some bypass capacitors between the power supply and signal
grounds (including the A/V shields if there are A/V connectors). It is
possible for a failure to result in a serious safety hazard where the RF
(antenna/cable) or A/V connectors become electrically live.
|NotTaR of Television Sets : Shock and/or spark when connecting cable..
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However, a tingle or small spark might be normal. RFI bypass caps between the
AC input and shield on the connector could result in some leakage - 50 V or
more might be indicated using a high impedance multimeter. This is harmless.
Reversing the plug in the AC socket (if it is not polarized or if you are using
an unpolarized extension cord) might eliminate or greatly reduce the effect.
Nonetheless, it should be checked out. Measure the resistance between each
side of the AC plug and the RF and AV connector shields. It should be 1 M ohm
or more. Test for voltage between the cable (or other device) connector and
earth ground. If there is anything significant, test the resistance on the
device between its shield and its power plug as above - other devices may have
RFI bypass caps or be defective as well.