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T240 Monitor Backlighting Issue

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    #1

    T240 Monitor Backlighting Issue

    Long time lurker, first time poster. Thanks in advance for any insight anyone might have!

    One of my friends gave me his Samsung T240 display because it stopped working. I said I’d look into why this might be happening. He’s actually purchased a new monitor, so this is mostly just an experiment, but I’d sure like to find out why this problem is happening. I have been referencing these posts (https://www.badcaps.net/forum/showth...highlight=T240, https://www.badcaps.net/forum/showth...highlight=T240), but my problem appears a little different.

    Symptoms:
    The monitor turns on for a second or two, displaying the Samsung logo. However, shortly thereafter, the backlight turns off and the screen won’t display a picture. I can get similar behavior to occur when hitting the ‘source’ button. It doesn’t look like the backlight is totally out because it would ever light the panel, if that was the case. During the problem, the power light on the front is on.
    Here is a youtube video of what is happening: http://youtu.be/7u-i_inT2RE



    What I have done so far:
    • Currently, I have the panel disassembled and have looked over the power supply. The panel is only 2-3 years old and was very well taken care of. The caps look to all be in very good shape.
    • I have checked for shorts on U202 (see last picture, small 5-pin in middle), none.
    • I have checked for shorts on the other IC, none.
    • I WANT to check if T301 is okay, but don't know how to test. Can't find data sheet, either.




    Component Conditions:
    • No apparent bad caps (no bulging, leaking from top or bottom)
    • No big burn marks on any components
    • Slight browning of the PCB’s underside (trace side), though nothing looking too drastic
    Attached Files
    Last edited by mucoast; 09-03-2011, 01:24 PM.
    Tags: None
    #2
    Re: T240 Monitor Backlighting Issue

    Please verify if this is the common problem known as "two seconds to black". With a flashlight or other bright light at a flat angle, see if the screen is still showing an image after the backlight goes off.

    TSTB can be caused by bad caps, bad inverter transformers, failing CCFL tubes, and other stuff. I'd check the inverter transformer first, mainly because I've got a board with an earlier version of that TM-10160 transformer laying on a shelf because of an open winding.

    Comment

      #3
      Re: T240 Monitor Backlighting Issue

      Yep, verified. I hooked it up via DVI to my small server and, upon powering on, I saw the full screen.

      A second or two later, the screen went dark. With the help of a trusty maglite I could see that the logon window was still displayed, just too dark to read without the light on it.

      On a side note, I saw this: https://www.hobbymods.com/store/inde...ent-parts.html

      Wondering what kinda caps they provide. Not a bad price, but wouldn't want to trade crap for more crap.

      Comment

        #4
        Re: T240 Monitor Backlighting Issue

        I believe your board has had problems with the the inverter transformer, T301. Hint: If you look on Ebay, there's at least 5 sellers selling replacement transformers. Try checking the secondaries of the transformer. With your meter set on resistance, place your probes across the yellow points and then across the red points. Difference between the two readings should be no more than 3%
        Attached Files

        Comment

          #5
          Re: T240 Monitor Backlighting Issue

          epic.


          YELLOW POINTS: 935 Ohm
          RED POINTS: .594 MOhm (WOW)

          So one of the transformer secondaries opened up?

          Comment

            #6
            Re: T240 Monitor Backlighting Issue

            Originally posted by mucoast View Post
            epic.


            YELLOW POINTS: 935 Ohm
            RED POINTS: .594 MOhm (WOW)

            So one of the transformer secondaries opened up?
            Yes. Looks like you will have a nice monitor for very little money.

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

              #7
              Re: T240 Monitor Backlighting Issue

              So that was simple.

              I purchased a replacement on ebay, but the sellers are all in Hong Kong/ China. Argh, gotta wait till almost oct. for the part to come in.


              Also, one last question:

              That transformer is a large part, much bigger than the caps I am used to replacing. Is there any information you can provide on getting this big ole' part out? I have a WES51 soldering station, is that sufficient?

              Comment

                #8
                Re: T240 Monitor Backlighting Issue

                Using a solder sucker or solder wick on each individual connection should do the trick. Once most of the solder is out of the way, apply lots of flux, then quickly run your soldering iron over all pins on one side until the solder is soft on all of them, remove that side from the board, then do the same for the other side.
                Originally posted by PeteS in CA
                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                A working TV? How boring!

                Comment

                  #9
                  Re: T240 Monitor Backlighting Issue

                  I have a feeling that the wick might be a better choice. I can just plop the wick over the connection, heat it up and get most of it out.

                  However....ill probably just buy both to be safe.

                  Seriously, if this fixes the monitor, I am going to crack up laughing. Ill see if my friend can return his new monitor!

                  Comment

                    #10
                    Re: T240 Monitor Backlighting Issue

                    Don't mean to kinda jack this thread but I am having the same issue. I have a t240 that turns on for one second and then off goes the backlight.

                    I have been trying to figure out how to take the stupid thing apart for a while now. I now I feel like the stupid one.

                    I figure you put like a small flat blade into the slits on the sides on the back but I can't get the center part of the stand holder to come off.

                    Pictures attached of my monitor. Any help would be great.
                    Attached Files

                    Comment

                      #11
                      Re: T240 Monitor Backlighting Issue

                      There are probably two screws in those holes in the stand. Take those out, take the back of the stand off, and then there are probably at least two more holding the bottom of the monitor together. Don't use a screwdriver to pry, they scar the plastic. There are plastic tools for that, and credit cards and guitar picks sometimes work.

                      Comment

                        #12
                        Re: T240 Monitor Backlighting Issue

                        There were 2 screws on the front of it that I had already removed them. However it turns out I was just to worried about breaking it. The base piece just slide out (with a little prying). and found the other 2 screws.

                        Now I dont feel so dumb, just kinda
                        Attached Files

                        Comment

                          #13
                          Re: T240 Monitor Backlighting Issue

                          Yeah, I have one of these T240 on my desk - really sweet monitor, hard to get one these days with 1920x1200 resolution.

                          The leg is hard to mount and hard to pull out, makes you worry you'll break it, and the way the case is made just sucks as you almost can't open it without damaging the case.

                          Comment

                            #14
                            Re: T240 Monitor Backlighting Issue

                            On most monitors you can ease up the top or bottom of the Surround from the Screen,and that can then let you put in a flat object to open the rest up.

                            Comment

                              #15
                              Re: T240 Monitor Backlighting Issue

                              When I took mine apart yesterday, I took some video. I talk about how I got the panel apart, as well as how to remove the components to get to the power supply. If youll be patient, I will put it up on Youtube later this afternoon.

                              THe long and the short of it is this: After taking out the stand and the two screws on the bottom-center of the back of the panel, put a screwdriver in either slot on the back of the panel (use a large one to get a lot of leverage). Pry the back panel up until it pops on either side. Then, work your way from the non-menu side all the way around to the side with the pushbutton menu. This worked fine for me, though I am pretty sure its impossible to do without a few scuffs on the glossy-black finish...

                              Comment

                                #16
                                Re: T240 Monitor Backlighting Issue

                                Got mine all the way apart. I was hoping it was just the capacitors but it looks like it is something like the guy who started this thread.

                                Brown marks on the board.
                                Attached Files

                                Comment

                                  #17
                                  Re: T240 Monitor Backlighting Issue

                                  Scorching like that isn't good, but it doesn't mean the transformer is bad. Check the output windings with an ohmeter. I'd also replace all the caps except the largest. It's possible that failing caps are causing the transformers to fail. Or the transformers are just badly made.

                                  Comment

                                    #18
                                    Re: T240 Monitor Backlighting Issue

                                    http://youtu.be/_UEGD-uhkTo

                                    Probably not needed anymore, but goes over a few more details of taking the monitor apart.

                                    Comment

                                      #19
                                      Re: T240 Monitor Backlighting Issue

                                      Measured the resistance between the points like above:

                                      Red: .930
                                      Yellow: .605

                                      Comment

                                        #20
                                        Re: T240 Monitor Backlighting Issue

                                        Originally posted by coreyc123 View Post
                                        Measured the resistance between the points like above:

                                        Red: .930
                                        Yellow: .605
                                        Bad transformer. Plenty of information on getting a replacement in this thread.

                                        PlainBill
                                        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                        Comment

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