Question about Panasonic CT25G7 25" TV

1 Answer

No vertical deflection,only a thin horizontal line.

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.

Wally

dede27@norwaymi.com


Posted by on

  • dede27 Feb 22, 2009

    Hi Shuttle,



    Thank you for your help! Sorry it took so long to answer. I had trouble with my PC and then the password. I contacted Fixya and they gave me a new one.



    After reading your comments, I went back and looked at the Service Bulletin. It said to "Replace C553(P/N ECEA2EU220) and add a 10UF/250V electrolytic capacitor (PN ECEA2EU100) across it on the underside of the board."



    I don't know what I was thinking. I figured the two capacitors were in parallel so I put in one 32UF/250V capacitor. I did not realize at the time, C553 was a special capacitor and that's why the bulletin had a special installation procedure.



    Do you think this had something to do with burning out the IC?



    Recently I was told I should have put in an IC 451 Vertical Output kit and it not only had the IC but also the associated capacitors, resistors, etc.



    Do you know what those components are? If so, would you please tell me what they are or where I could get the kit?



    I have an extra IC 441 Vertical Output. I do not want to put it in until I have hopes of finding out why the other one burned out.



    Regarding the vertical deflection coil: If it were shorted, one would think the picture would have been distorted after I had put in the new parts. When I started the TV it had a nice picture. There was no distortion at all.



    Again,thank you,

    dede27

  • dede27 Mar 15, 2009

    Again, thank you Shuttle!



    I did not know there is such a thing as "auto correcting circuits". I'm indebted to you for your time and expert help.



    Did you read my reply to the other man and, if so, what are your thoughts on my reply to his post? I'd especially like to know if there is such a Vertical Deflection kit and where would I get it ?



    I had been told the kit contains all the components that could go bad. Do you know what they are?



    Many thanks for your much appreciated help!

    dede27

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Hello dede27,

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,

Thank you,

Shuttle83

http://www.electron-age-technologies-llc.com

Posted on Jan 30, 2009

  • Henry McKelvey
    Henry McKelvey Feb 25, 2009

    Hello dede27,



    In reply to your statement:

    Regarding the vertical deflection coil: If it were shorted, one would think the picture would have been distorted after I had put in the new parts. When I started the TV it had a nice picture. There was no distortion at all.



    This is not necessarily true or false, because it depends is you TV has auto correcting circuits as some TV do, If the coil was to develop a short which causes excessive current to flow and a lowering of the deflection signal, the circuit would auto correct and make the picture appear normal until the problem was so bad that the auto correction circuit could not make up for the distortion. You have indicated in your first statement that the picture had some distortion:

    "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."

    This statement lead me to believe that auto correction was being done in this case, or a component was developing a charge as it played and warmed up.



    I hope that I did not mis-lead you in your efforts, I just wanted to cover as may possiblities as I could with the least amount of technical jargon.



    Thank you,



    Shuttle83



    http://www.electron-age-technologies-llc...

  • Henry McKelvey
    Henry McKelvey Mar 16, 2009

    Hello dede27,



    Yes many electronics parts stores now put together such kits for well known problems. I have always first tried to do troubleshooting and then parts replacement checking the waveforms and signal levels before concluding a repair job, These kits are helpful because they contain "most" of the parts that need replacing, but nothing beats a good and complete troubleshooting job on electronic devices.



    Thank you,



    Shuttle83


    http://www.electron-age-technologies-llc...

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