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bobo60 09-15-2009 03:15 AM

Degaussing a tv
 
hi,

i have a 20" rca color tv, that i need to degauss. its only about 6 yrs old, would think it would have a degaussing coil built in, but if it does, it must not be working. anybody know where i can get a deguassing coil? i have and old turntable that i could disect, and pull the moter out, and remove the armature, and try that to deguass the set, but i really dont want to tear apart the turntable. i looked online , and places like radio shack, best buy, dont even list them. thanks.

bob

DangerMouse 09-15-2009 05:47 AM

ANY color TV that has a picture tube has a demagnetizer in it.....it only fires/demagnetizes when your TV has been OFF for 20 minutes or longer, it fires up when the power is turned on....

That means you should see a CHANGE in the picture over a period of days....IF it still hasn't changed in a 3-4 day period, you may want a TECH to check your degaussing circuit.....
I would suspect a bad thermistor or relay drive/timer circuit or bad connects >>IF<< it doesn't change over 3-4 days......

maybe this will help?

DM

micromind 09-15-2009 08:12 PM

A TV form 6 years ago almost certainly has a thermister in series with the degaussing coil control. It works like this;

1) when power has been off for a while, the thermister is at room temperature.

2) when the set is turned on, the cold thermister allows a large amount of current to flow in the degaussing coil, thus degaussing the picture tube.

3) the thermister quickly heats up, and as its temperature rises, so does its resistance.

4) In a second or two, the thermister will reach its point of equalibrium. The current flow through it will maintain its temperature. This current is very low, so the coil is barely energized.

5) When the set is turned off, the current flow stops, and the thermister cools.

Most of the time, the thermister burns up. Sometimes, the coil wires break, it's rarely anything else.

A word of caution, if you go poking around in the back of a TV, there are capacitors that can store a lethal charge, even if the set has been off for several days. Stay away from the thick wire that goes to the screen side of the picture tube, usually on top. It operates at about 1000 volts per inch of tube size.

Rob

P.S. A TV tech can troubleshoot and fix this pretty easily.


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