[mythtv-users] OT - Life without MythTV
beww at beww.org
Mon Feb 25 21:25:00 UTC 2008
On Feb 25, 2008, at 1:30 PM, Bill Omer wrote:
> Other than leaving the set unplugged for several hours, is there
> way? I've heard that some caps that just wont discharge unless you
> short them.
The usual way is to use a "chicken stick", sometimes known as a "Jesus
stick". This is basically an alligator clip on one end of a well-
insulated wire with a high-voltage type probe at the other end.
Technically it should have a resistor to limit current flow but a lot
of them don't have this. You slip the probe under the rubber cap of
the connector on the CRT.
If you pop the HV connector of the CRT (carefully), then touch the
metal part to the chassis before working on the xfrmr it usually
discharges any residual HV.
To be honest, most capacitors used in today's consumer units are so
crappy they don't hold a charge for long.
>> You really should measure the high voltage after a flyback
>> replacement, but I suspect you do not have a voltmeter designed for
>> upwards of 20K volts.
> I've read 50kV. Deadly ... easily. By far not a safe project IMHO.
Usually around 26-33 Kv. Not generally "deadly" as there is not
enough current there to kill you except under unusual circumstances,
but it hurts like blazes, I know :-(
Now the power supplies in High-power TV transmitters are another
story. That's why we called them "Jesus sticks", when you shorted a
cap that somehow didn't get discharged by the interlocks and saw the
arc you would often say "Jesus, that could have been me!".
One reason for checking the voltage is that you can get X-Ray emission
if the voltage is too high, but most sets these days have overvoltage
sensing and shutdown circuitry.
Just be careful if you don't have experience with such things.
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