Question about Toshiba 51H84 51" Rear Projection HDTV-Ready Television
For a while there is a loud snap and the screen goes out ( less than .5 sec )
It sounds like static . It is now quite often. I removed the back cover and there was bright spark from one of the 3 circuit boards. It appears on the board but not always in exact same area of board.
TV's use high voltage to generate the stream of electrons traveling
across the picture tube hitting the screen and lighting it up (thus the
name Cathode Ray Tube). It takes about 25,000 volts to do
this. In normal air, it takes about 1000 volts to jump an inch of
air, so the high voltage transformer needs to have good
insulation. It generates the voltage through a technique of
charging the transformer's magnetic field with a low voltage of about
140 volts then letting it go where upon it flys back out the high
voltage side at much high levels (Thus the common name
flyback). A most common failure in a CRT type TV is for the
insulation to crack in this transformer which is a unique component for
each model of TV and leak out the current overstressing the circuit
driving it. You can liken it to a little bolt of lightning
getting loose in the circuit and has the same sound on a smaller scale.
It would be well to replace your flyback transformer before it gets worse and blows up something else as well. Best done by a professional used to handling high voltage. The picture tube can retain voltage even when the TV is unplugged for some time, and replacing the anode lead (the big red one) can be dangerous.
Hope Ya Fix It!
Posted on Jan 09, 2008
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