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50V AC coming from RF connector
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Posted to sci.electronics.repair
Andy Cuffe
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50V AC coming from RF connector
On Thu, 20 Sep 2007 09:41:05 -0700,
wrote:
Got a tester from electrician and tested all sockets all had correct
polarity and grounding. Electricians checked the ground and neutral
to copper pipe and all was good there as well. I'm leaning towards TV
is suppost to do this but no concrete proof yet.
It's completely normal. Many TVs (particularly cheaper ones) have a
hot chassis. This means that the chassis is connected to the power
line and has voltage on it compared to ground. The tuner input is
isolated from the hot chassis with a network of capacitors and
resistors that block the line voltage, but pass RF. If you measure
the voltage with a typical volt meter it will show a voltage, due to
the meters high input impedance. As soon as you ground the RF
connector the voltage will disappear. If this isolation network
failed, you'd know it when you connected the cable (loud bang, lots of
sparks, blown fuses...).
Andy Cuffe
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