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Panasonic 27sf14v1 no video/sound

One morning I turned my TV on and nothing on the screen nor I can hear anything from the spekers. I hear the relay clicking when I turn it on or off. I have replaced the horizontal output with an NTE2331, thought it would fix the problem. What else should I do?

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  • MWTech Oct 09, 2008

    Thank you for the info. I'm not really good about fixing tvs and still learning on how to fix them. It's a new hobby that I'm getting into. But base on what you are telling me, I'm confuse on where to put my leads in testing the components. I know for sure that I am not getting the voltage on the horizontal output checking on the collector and emitter. Really I don't know where the low voltage power supply is located. I'm going to test somethings out.

  • MWTech Oct 09, 2008

    Update. I was checking the voltage on the horizontal output in AC mode. I have 183V DC on the horizontal output. I've checked for cold solder joints and found a few, but still the same.

  • MWTech Oct 10, 2008

    I've done what you have told me to do. Resolder the small transformer and small transistor traced from transformer. I have tested the transistor which come to find out it's the horizontal deflection driver and I got these readings as my meter is set to diode reading.

    Red lead on Base, Black lead on Collector = OL

    Red lead on Base, Black lead on Emitter = OL

    Black lead on Base, Red lead on Collector = OL

    Black lead on Base, Red lead on Emitter = .597

    Red lead on Emitter, Black lead on Collector = .572

    Red lead on Emitter, Black lead on Base = OL

    Black lead on Emitter, Red lead on Collector = OL

    Black lead on Emitter, Red lead on Base = OL

    Red lead on Collector, Black lead on Base = OL

    Red lead on Collector, Black lead on Emitter = OL

    Black lead on Collector, Red lead on Base = OL

    Black lead on Collector, Red lead on Emitter = .572

    From google searching on how to check a transistor, these are the readings. I put it back in and still not working. Does the transistor seem bad? All I remember is that if it's shorted, then replace it. I might be wrong though.

  • MWTech Oct 11, 2008

    I took some pictures of the TV I'm working on. Hope some of these help.



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While the horizontal output is often the culprit you need to check some other things out first before jumping in and changing parts. Many sets, due to the high voltages and high amounts of heat they produce are prone to having bad solder connections. Look around the horizontal transformer for one leg than may be loose/desoldered. Also check the connections on the relay, they can come loose (you may even see some black charred discoloration) from repeated on/off cycles and the heat/cool that happens in the sets normal life. Also look at the connections at the flyback transformer. Re-solder all that are not nice and shiny.
If you have a DC voltmeter, verify that you are getting your B+ voltage (approx 160V )up to the horizontal output. If not, look to the low voltage power supply. If it's there and still nothing and all the connections look to be good, check the horizontal drive transistor (smaller transistor that feeds the signal to the base of the horiz. output).

Probably 80%of the time you'll find a bad connection and be off and running again. While you're in there, re-solder the vertical output ic as a precaution. Panasonics (and other brands) are known for the legs of those ics getting loose.

Posted on Oct 07, 2008

  • Inno Laur Oct 09, 2008

    The low voltage supply will be around where the AC power cord connects to the set. There will be a quite large (compared to others in the set) black electrolytic capacitor in this area and you can (carefully) check for voltage at it's leads on the underside of the board. It should be around 160V DC.

    In general, when testing for voltages around the circuit board you need to find a good ground, the case of the tuner (shiny chromed box that the cable connects to) is a good place to reference your ground from. From there you can secure your negative meter lead and just move around with the positive lead to check for different voltages.

    It's difficult to give accurate information when I can't actually see the set. Troubleshooting TVs is kind of a process that technicians develop over the course of years. I start by looking very closely for bad connections (as they are very common) in certain areas and also for any obviously burned or discolored components. A picture is worth a thousand words, that definitely applies here. Not sure if you can post pictures on this website. After that I start chasing voltages around the board, starting with the power supply as outlined. Without that B+ voltage you won't have anything.
    If you have 183V on the horizontal output then I'd say you have that but probably no horizontal drive. From the base of the horizontal output you can trace back to a small transformer (the horizontal drive transformer) which generally doesn't fail itself but it is prone to cold solder, sometimes not that obvious. I'd touch up the solder just to be sure. From the primary side of that transformer you can trace back to a smaller transistor (smaller than the horiz. output) which takes the hoiz pulse from the processor IC and pre-amplifies it for the output. Check to make sure it's both soldered properly and meter it for defects. On the diode setting of your meter, connect the black lead to the base. Connect the red lead first to the emitter, note the reading, then to the collector, note the reading. Then reverse things, with the positive lead on the base, black lead to the collecter then emitter and note the readings.

    Sounds like you have some electrical/electronic skill and the necessary tools so I will continue to help you as much as I can. Let me know what you find and I'll see what I can do.

    Good luck!



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