Question about Panasonic CT25G7 25" TV
I would appreciate any help I can get for the following problem:
My television set is a Panasonic CTN 2766S and chassis APEDP204.
Problem: The top of the picture was a couple of inches short when the tv was first turned on. After five minutes or so, the picture filled out to normal and stayed that way.
It did this for about a year and then when the set was turned on, it only had a horizontal line in about the middle of the screen. It did not fill out no matter how long it was on.
I replaced the IC 451(LA7836-TV) “VERT OUT” and, also, replaced C553, 22UF/250V with a 32UF/250V capacitor because a service bulletin said the capacitor was drying out. That caused an increase in beam current resulting in a broken CRT neck.
When the tv was turned on. The raster filled out except for the top couple of inches. Adjusting the vertical size pot did not have any effect. IC 451 was getting hot in a short time. After 30 minutes the raster did not fill out, like it had done previously. I heard a sound like something was shorting out and the raster disappeared leaving only a horizontal line on the screen.
I made a check of IC 451 and found it was shorted.
Again, I would appreciate any help with this problem.
Hi and welcome to FixYa,
A few ideas you may want to consider/explore;
Posted on Jan 30, 2009
I suspect you have some background in electronics so I'll ask you some questions.
First, I know that you changed the output ic and a capacitor, the capacitor caused excessive beam current, that's bad, remember that beam current is dangerous because it can produce X-Rays. Remember to use the exact value of parts for X-Ray generating areas of the TV. So replace the C555 with the rated value by the manufacture.
As far as the vertical deflection problem it sounds like you may have a shorted vertical deflection coil (part of the yoke transformer). I would suggest testing the coil to see if it is shorted (A ring test will determine this). The Sencore LC102 has a ring test feature or you can lookup how to build a simple ring tester. In any event replace the IC and test the yoke transformer for shorts on the vertical winding.
I hope this helps,
Posted on Jan 30, 2009
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