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Samsung 940bw

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    #1

    Samsung 940bw

    Hello,

    I have this problem. Monitor went black while surfing, no noise, just off. Tried flashlight trick and no joy.

    I have to date:

    1. Replaced all but two caps, the small 47u and the large cap. (In process of replacing the 47u, grasping at straw).
    2. Powered up monitor (prior to 47u removal) and screen dark, but, now I can see the desktop with a flashlight.
    3. Tried known good lamps and no joy.
    4. Capacitors from local electronics supply, NTE 105c type. Apparently this is pretty common as they say they sell tons of these to the LCD repair guys.

    Question is what is the next most common item to fail preventing the lamps to light up? And where can I purchase these items?

    I'm having a bit of fun messing and learning with this thing but haven't pinned down whether the fuse(s) are bad or one of them MOSFET thingys.
    I have noticed that one MOSFET by its self has a lead that is not soldered, the one next to the vcc which has printed on the board "high".



    Thank you in advance.

    Link to picture of my board if needed.
    https://docs.google.com/open?id=0B_b...TZWdUQweWhCcW8
    Last edited by walking; 06-05-2012, 08:27 PM.
    Tags: None
    #2
    Re: Samsung 940bw

    Post clear focused pictures of all your boards following my sig file below exactly. We want picture composition like the following

    https://www.badcaps.net/forum/showpo...94&postcount=1
    --- begin sig file ---

    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

    --- end sig file ---

    Comment

      #3
      Re: Samsung 940bw

      "I have noticed that one MOSFET by its self has a lead that is not soldered, the one next to the vcc which has printed on the board "high"."

      Perhaps its my tired eyes, bur the above I cannot see from the Photo,you need to add photos as advised by retired caps,
      You have not mentioned measuring the resistance of the Inverter transformer secondaries, and that should be your next Move.

      Comment

        #4
        Re: Samsung 940bw

        If you mean IC601 it is sometimes mounted like that on this board. Close up picture please.
        To test the inverter transformers see here:http://lcdparts.net/TransformerDetai...ProductID=2724
        Set your meter on ohms 2000. (power to the monitor off for 5 minutes)
        Measure across S1 to S2 and S3 to S4 on each transformer and post the results.


        EDIT also check the fuse at FH602 = Power off meter on resistance 20 ohms - post result
        should be the same as touching the probes together
        Last edited by selldoor; 06-06-2012, 04:06 AM. Reason: Fuse
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

          #5
          Re: Samsung 940bw

          Originally posted by selldoor View Post
          If you mean IC601 it is sometimes mounted like that on this board. Close up picture please.
          To test the inverter transformers see here:http://lcdparts.net/TransformerDetai...ProductID=2724
          Set your meter on ohms 2000. (power to the monitor off for 5 minutes)
          Measure across S1 to S2 and S3 to S4 on each transformer and post the results.


          EDIT also check the fuse at FH602 = Power off meter on resistance 20 ohms - post result
          should be the same as touching the probes together
          Ok, Transformers are both @ 600-609 per S1-S2,S3-S4. And P1-P2=.6 (there is no P3-P4. Single center winding.

          Fuse FH602=no cont. over resist. blown...
          Fuse FH601=.5

          Thanks.
          Last edited by walking; 06-07-2012, 01:09 AM.

          Comment

            #6
            Re: Samsung 940bw

            Fixed it...one bad MOSFET in addition to the fuse.

            Comment

              #7
              Re: Samsung 940bw

              which one?

              Comment

                #8
                Re: Samsung 940bw

                Originally posted by walking View Post
                Fixed it...one bad MOSFET in addition to the fuse.
                Well done!

                As Bocca says - "which one" if it was the I601 on its own that is ok if it was one of the pair it is usual to change both. We like this sort of info to help others in future.
                Please upload pictures using attachment function when ask for help on the repair
                http://www.badcaps.net/forum/showthread.php?t=39740

                Comment

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