I have troubleshooting sony tv 29 inches having pincushion problem at the right side of picture. At first time it was turn on it is small dark and then dissappar in a few second and it will comeback again.
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I assume that the pincushion problem to your TV, ie, the display have curved vertical lines [X] shape. If so, the pincushion circuit should be troubleshooted. Check the transistor of this stage. Try to download the repair manual to this set. It will have all details. Is it a Sony TV? If so, try this link. http://electronicshelponline.blogspot.com/Pull up older posts.
The pincushion it intimately related to the horizontal circuits,the electron beam must travel farther to reach the corners of the crt and it does to the middle and so without pincushion circuits the raster would be bowed in on the sides on crts 27 inches are larger.Pincushion corrections straightens the raster by modulating the horizontal yoke current at a vertical rate.In an RCA tv the pincushion circuits are usually numbered 4800and the pin amp will probably be numbered 4801,its drive transistor should be Q4802,R4802 will be the width control,and R4805 the e/w pin amplitude. its inputs from the vertical should be Q4801 (subtractor) Q4803 (buffer) you should have a parabola waveform at 4801,yoke current can be modulated here without effecting high voltage.when Q4802 conducts voltage should decrease across Q4801 and the voltage drop across the yoke increases. The east west pin amp control 4805 controls how much of the vertical parabola is input to U4801 to compensate for changes in width caused by variations in beam current.By varying the e/w control resistor you can know if the circuit fault is in the input or output,if the picture varies in size the fault is in the input to U4801,if it does not vary check the output or U4801......hope that helps
The picture on my projection TV has intermittent concave right and left sides.
Can you tell me what's wrong with it?
your problem is due to pincushion ckt
as it is intermittent so that there might loose contact or print break in pincushion ckt
it can be rectified easily by skilled tech.
there is no parts failure.
Lets try something before you call for a second opinion,with the tv ON and the problem showing hit the top and side of the tv,if the picture somehow reacts or corrects itself when you hit it call someone else and tell them what the problem is and that you feel it has a loose conection,dont have to tell them about the first estimate.
Dont hit the tv with a hammer,just with the palm of your hand.Is worth the try.