Samsung 2253BW inverter problem.

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  • FrankMtl
    Member
    • Sep 2015
    • 36
    • Canada

    #1

    Samsung 2253BW inverter problem.

    Hi, this is my first post.
    I repaired a few LCD as a hobby before.
    But this Samsung is a difficult one.
    I replace all the caps (10) and still nothing on the screen.
    All I have is the blue power led.
    I test the diodes and they check ok.
    What could it be?
    I can hear a small squeal when I put my ears close
    to the board. The squeal appears to come from the 2 transformers ?
    And when I turn on the monitor the squeal goes away.

    Thanks.

    Frank.
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Samsung 2253BW inverter problem.

    Any good clear pictures of the bottom side of the board?
    Did you check green fuse next to one of the inverter transformer?
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

    • FrankMtl
      Member
      • Sep 2015
      • 36
      • Canada

      #3
      Re: Samsung 2253BW inverter problem.

      Hi, no I didn`t check that fuse.
      I learn something today, I didn`t know that was a fuse.
      I didn`t check the other T3 fuse either..

      Can I check it on the board?
      I check my diodes on the board and was able to read them, but from what I read it`s not the best way to do it.

      Wich function do I use on my multimeter to check it?
      My multimeter is really basic and doesn`t have continuity on it... not good...
      Can I use the diode function to test the fuse?

      Thanks.
      Attached Files
      Last edited by FrankMtl; 09-24-2015, 09:13 PM.

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #4
        Re: Samsung 2253BW inverter problem.

        Ohm mode, no power to the board.
        Touch your meter probes together so it will show the reading on the meter, it should be <1 Ohms, now put the meter probes on each end of the fuse, it should show the same reading as when you touch the two probes together.
        I do not use continuity for testing fuse since the meter will beep with resistance as high as 50 Ohms or more. The fuse may have high resistance but may not be completely open circuit. Continuity does not tell you if you have good connections between point A and point B, it just tells you you have connections.
        Last edited by budm; 09-24-2015, 09:21 PM.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment

        • FrankMtl
          Member
          • Sep 2015
          • 36
          • Canada

          #5
          Re: Samsung 2253BW inverter problem.

          Thanks, I set my meter at 200 Ohm and touch the probes together
          it gave me 00.3. When I test the fuse with no power on board
          it gave me 140.33 something high like that??

          Strange I just retest 5 minutes after my post and now it reads 1.
          ..
          Now it read 139.8 ..

          I should mention that my multimeter is manual not auto range.

          Thanks.
          Frank.
          Last edited by FrankMtl; 09-24-2015, 10:10 PM.

          Comment

          • FrankMtl
            Member
            • Sep 2015
            • 36
            • Canada

            #6
            Re: Samsung 2253BW inverter problem.

            Hi, I bought I glass fuse 4A to replace that green fuse.
            Now even the power led doesn`t work?
            Can I replace this type of fuse with a glass fuse?
            Both are 4A.

            Thanks.
            Frank.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Samsung 2253BW inverter problem.

              The original green fuse has blown for reason, more likely that you have bad power MOSFETs (the two 8-pin SMD on the bottom side of the board) which drive the inverter transformer.
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

              Comment

              • FrankMtl
                Member
                • Sep 2015
                • 36
                • Canada

                #8
                Re: Samsung 2253BW inverter problem.

                I see, youre correct I tested the green fuse and it showed 1. on my multimeter.
                But could it be me that blow it with the heat from my soldering iron?
                I see the 2 mosfet that you are talking about, I don`t think I have
                the soldering iron to do this. This is so small.
                Maybe I will buy another power supply.

                Thanks.

                Frank.

                Comment

                • Joe Black
                  eager to learn
                  • Sep 2015
                  • 173
                  • southeastern europe

                  #9
                  Re: Samsung 2253BW inverter problem.

                  If you have not gave up yet, check the "transistor-like"components fitted on the metal "radiators".
                  Those are the power mosfets, and small SMDs that you got afraid of actually drive them-tell them how fast to switch.

                  Anyway, you should read the model of MOSFETs, and google their multimeter readings.

                  Most likely, one has failed. Report back with results.

                  Never just replace fuse, or even a MOSFET for that matter. We should always check WHY something has failed, and act accordingly.

                  note: not an expert. I stand corrected for anything I state wrong, of course not intentionally. Also, sorry for bad grammar.

                  edit:
                  If all MOSFETs test OK (out of circuit) check graetz bridge, and any diodes you may overlook.
                  Maybe that C113 was there, and you forgot to put another one?
                  Last edited by Joe Black; 09-25-2015, 10:37 PM.
                  stay classy

                  Comment

                  • FrankMtl
                    Member
                    • Sep 2015
                    • 36
                    • Canada

                    #10
                    Re: Samsung 2253BW inverter problem.

                    Hi, don`t worry there were no caps in C113 :-)
                    This is not my first LCD repair but the hardest for sure.
                    Well at least I`m learning.
                    Can I test MOSFEST`s on the board? Or do I have to remove them?
                    To be sure you are talking about the 3 black thing with 3 legs?

                    Thanks.

                    Frank.

                    Comment

                    • FrankMtl
                      Member
                      • Sep 2015
                      • 36
                      • Canada

                      #11
                      Re: Samsung 2253BW inverter problem.

                      Hi, here is what I found 2 transistors MBR20100CT
                      and one FET DMO565R.
                      So they are not MOSFET ?

                      Thanks.
                      Frank.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Samsung 2253BW inverter problem.

                        The MOSFETs that you need to check are those two SMD one, the fuse feeds those two MOSFETS so the problem is not in the main power supply section. If you remove that fuse you just install then you should have your power LED back on.
                        Never stop learning
                        Basic LCD TV and Monitor troubleshooting guides.
                        http://www.badcaps.net/forum/showthr...956#post305956

                        Voltage Regulator (LDO) testing:
                        http://www.badcaps.net/forum/showthr...999#post300999

                        Inverter testing using old CFL:
                        http://www.badcaps.net/forum/showthr...er+testing+cfl

                        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                        http://s807.photobucket.com/user/budm/library/

                        TV Factory reset codes listing:
                        http://www.badcaps.net/forum/showthread.php?t=24809

                        Comment

                        • FrankMtl
                          Member
                          • Sep 2015
                          • 36
                          • Canada

                          #13
                          Re: Samsung 2253BW inverter problem.

                          Thanks, you mean the 2 8 legs chip under the board right?
                          Label STM8309 ?
                          I don`t think I can solder this , it`s to small.

                          Frank.

                          Comment

                          • stj
                            Great Sage 齊天大聖
                            • Dec 2009
                            • 30937
                            • Albion

                            #14
                            Re: Samsung 2253BW inverter problem.

                            you can,
                            put some solder across the pins on one side,
                            slide the iron up and down the pins while gently levering it up from the side wih a blade.
                            once it lifts a bit, remove the solder wih some braid and do the other side the same way.

                            Comment

                            • FrankMtl
                              Member
                              • Sep 2015
                              • 36
                              • Canada

                              #15
                              Re: Samsung 2253BW inverter problem.

                              Hi, I`m more worried about soldering a new chip.

                              Frank.

                              Comment

                              • stj
                                Great Sage 齊天大聖
                                • Dec 2009
                                • 30937
                                • Albion

                                #16
                                Re: Samsung 2253BW inverter problem.

                                put it on the same way and remove excess with braid if your iron is big.

                                Comment

                                • FrankMtl
                                  Member
                                  • Sep 2015
                                  • 36
                                  • Canada

                                  #17
                                  Re: Samsung 2253BW inverter problem.

                                  Thanks for the tip.

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #18
                                    Re: Samsung 2253BW inverter problem.

                                    You can check the resistance between S pins and the D pins of the MOSFETs with Ohm meter to see if they show low Ohms readings.
                                    Attached Files
                                    Never stop learning
                                    Basic LCD TV and Monitor troubleshooting guides.
                                    http://www.badcaps.net/forum/showthr...956#post305956

                                    Voltage Regulator (LDO) testing:
                                    http://www.badcaps.net/forum/showthr...999#post300999

                                    Inverter testing using old CFL:
                                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                    http://s807.photobucket.com/user/budm/library/

                                    TV Factory reset codes listing:
                                    http://www.badcaps.net/forum/showthread.php?t=24809

                                    Comment

                                    • Joe Black
                                      eager to learn
                                      • Sep 2015
                                      • 173
                                      • southeastern europe

                                      #19
                                      Re: Samsung 2253BW inverter problem.

                                      Ugh, sorry if I confused you, Frank.
                                      I promise I won't post anymore while leaving to work

                                      So, using the datasheet that budm neatly attached, locate (S)ource and (D)rain pins. Normally, Ohm resistance between those is infinite. If shorted (low Ohms), MOSFET is gone.

                                      Also, I have developed a habit of resoldering inverter transformer pins on every board I get to. It's generally good idea to carefully examine solder joints on all components and check for cracked or insufficient solder joints.
                                      stay classy

                                      Comment

                                      • FrankMtl
                                        Member
                                        • Sep 2015
                                        • 36
                                        • Canada

                                        #20
                                        Re: Samsung 2253BW inverter problem.

                                        Hi, thanks , I check to the MOSFET and one shows 0.06 between the S and D pins
                                        The other Mosfet shows 123 between the pins, So I guess this one is gone?
                                        Now I might try to solder this, first I have to google it to see how much is it.

                                        Thanks.

                                        Francois.

                                        Comment

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