Question about Sharp LC-26DV24U 26 in. LCD HDTV/DVD Combo

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By macafly on Mar 05, 2011 LC-26DV24U. Sound OK, White screen. Replaced Q413. No Joy. 12.8v on E, 1.55v on C, and 1.38v on B. 1.38v and 0.09v on either side of R518. 3.33v on 13 of cp401. Know just enough to be dangerous, but always willing to try and curious how thing work. If I short emitter/collector on Q413 I get picture, but I'm sure there is a reason for the circut. What's next? macafly14 days ago nothing obvious with the caps. pg e-3 says to check pins 1-5 for 5 v on cp2804. I've searched high and low and cannot find cp2804. at cp2802 pins 1-4 show 1.55v and pin 5 0.00v. Another note, This is the later "A" unit, and I have both service manuals. The "A" manual schematic shows 12v for pins 1-4. I don't understand the circuits, but it seems Q419 controls Q413 and J20 on IC2801 controls Q419. Mark macafly13 days ago pg e-3 of the service manual says to check pins 1-5 for 5 v on cp2804. I've searched high and low and cannot find cp2804. at cp2802 pins 1-4 show 1.55v and pin 5, 0.00v. Another note, This is the later "A" unit, and I have both service manuals. The "A" manual schematic shows 12v for pins 1-4. I don't understand the circuits, but it seems Q419 controls Q413 and J20 on IC2801 controls Q419. Thanks, Mark I've posted the original comment and offered $10 and received two broad answers. posted these comments back to each, but have not received any futher assistance. I presume either the digital PCB or power board will solve the problem, but don't know which to try or if their is a little more testing that can be done to solve the problem. thanks, Mark

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  • 8 more comments 
  • macafly Mar 21, 2011

    Q413 is on the power board. This set's T-con board is fastened to the bottom of the LCD screen assy. The parts breakdown does not list a part # for it. If I short the emmitter to the collector, I get a picture. As I've posted, I suspect, the scaler IC on the digital PCB, is the culprit, just don't want to waste money on the board if it is not the problem. Any more testing suggested?

  • macafly Mar 21, 2011

    http://www.mediafire.com/?h3fqacc16kh8j0... http://www.mediafire.com/?6487bi2r5nrsx9...
    Here are the links to the files. The top is the full manual and the lower is the "A" version which just has the update differences.
    Thanks,
    Mark

  • macafly Mar 22, 2011

    No, just the white screen. If I short the emmiter to the collector of Q413, then I get a picture, menu, etc..
    If I start a DVD, I get sound with the white screen, unless I short the e-c of Q413.

  • macafly Mar 22, 2011

    Thank you. Will get a board coming and let you know.
    Mark

  • macafly Mar 25, 2011

    Well, just received the replacement board, and no dice, acted exactly the same.
    What's next?

  • macafly Mar 27, 2011

    here's a short video on mediafirehttp://www.mediafire.com/?9bed8dbhdd63et... .
    I suspect one of a few things.
    1. the board I got has the same problem- seller says 100% checked OK
    2. I think it was Q419 that controls the base of Q413 is bad. It is a surface mount and I don't think I can get it changed (****, I can't hardly see it!!)
    3. The inputs to IC2801 that set the control to Q419 are the problem, at this point I'm lost. Don't understand the circutry and what the designers are tring to accomplish.

    On my own, I would probably try replacing the power board, but I'm just guessing at this point.
    More testing?
    Thanks,
    Mark

  • macafly Apr 03, 2011

    OK, I order the transistor and replaced it. Still the same. I have to admit ignorance, Emitter shows 0.0 V and Shows 0 ohms resistance to ground--like the schematic shows. 3.3V on the collector and 0.09V on the base and one side of R518. The other side of R518 is 1.38, same as the base of Q413. I'm baffled and over my head. What's next? What is the purpose of the circuit? Thanks,
    Mark

  • macafly Apr 04, 2011

    I'll see if I can find one and give it a shot. What happens if I just permantly short the E-C on Q143? Thanks,
    Mark

  • macafly Apr 20, 2011

    finally got a board found and ordered. Been swamped with work and family. Will let you know the results.
    Thanks,
    Mark

  • macafly Apr 23, 2011

    OK, received the board, didn't work at first. Found blown 404 picofuse. Replaced and Success!! Must be a bad cap or somthing. Thanks for your help,
    Mark

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  • 4,889 Answers

I believe the Transistor Q413 is on the T-con board? The one with the LVDS connector going into the display?

Posted on Mar 20, 2011

  • 8 more comments 
  • eagle338
    eagle338 Mar 21, 2011

    Ok read all the comments you have posted so far. By digital board of you mean main A/V board yes that seems like the problem to me too. Somehow I do not have the schematic for this particular model. If you can upload it to mediafire.com and get me the link to the file I will tell you if there is anything else you can do to confirm the location of the problem

  • eagle338
    eagle338 Mar 21, 2011

    I see that the Q413 controls the 12V line. When you have the white screen, are you able to bring up the menu?

  • eagle338
    eagle338 Mar 22, 2011

    100% possibilty that its a Digital A/V board issue. The fact that your tv works perfectly if the Q413 transistor is shorted confirms this. Replace the same and it should resolve your problem

  • eagle338
    eagle338 Mar 22, 2011

    Surething. Let me now how it goes

  • eagle338
    eagle338 Mar 25, 2011

    Thats weird. Its gotta be the Digital board. Let me make sure that I understand you correctly. Can you please upload a picture of the screen with the tv on?

  • eagle338
    eagle338 Mar 27, 2011

    Sufrace mount components can be replaced unless they are embedded into the board. I am about to log off now so I will check the video first thing in the morning and let you know

  • eagle338
    eagle338 Mar 28, 2011

    Oh ok now I get it. The picture is absolutely perfect when you short it. You say the surface mount transistor is faulty. It can be replaced by melting the solder and cleaning it up as soon as it melts so that the entire older solder is removed. You can then just solder the new one in. Does it look like this?
    http://members.cox.net/codesuidae/Transi...

  • eagle338
    eagle338 Apr 04, 2011

    The 12V line powers the backlight inverter and in the schematic I have seen that it powers the t-con too. I think it might be easier to just replace the power supply. Should not cost you more than 50-60$

  • eagle338
    eagle338 Apr 20, 2011

    Surething. Good luck :)

  • eagle338
    eagle338 Apr 23, 2011

    Glad to hear that :) Perseverance pays. Thank you for using Fixya.

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