Samsung LNT4069FX/XAA no picture with sound

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  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #21
    Re: Samsung LNT4069FX/XAA no picture with sound

    BTW, I looked at the formula for calculating the output voltage on the spec sheet, it looks wrong, it should be R2/R1 not R1/R2. The higher the R2 will cause more voltage of the ADJ pin to be be higher with ref to ground, thus higher output voltage, it works the same as LM1117 series except that it has Enable pin to turn the output on and off, unless this regulator does not function the same as the LM1117 series.
    IC107 is an adjustable regulator since it has 5 pins, the fixed regulator per spec sheet will only have 3pins, so retiredcaps is correct, the output of pin 4 is wrong, too low, it should be around 2.5V
    Attached Files
    Last edited by budm; 07-11-2012, 07:06 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

    • retiredcaps
      Badcaps Legend
      • Apr 2010
      • 9271

      #22
      Re: Samsung LNT4069FX/XAA no picture with sound

      Originally posted by ceconomon
      location -IC107 FRC board
      37302WU
      0735
      pin 1= 3.415
      pin 2= 3.415
      pin 3= 0.0
      pin 4= 1.847
      pin 5= 1.265


      Base on your analysis, it looks like I should be ordering the following part:
      http://www.digikey.com/product-detai...6-5-ND/1029402
      IC107 is bad. Pin 4 is too low and that might be causing circuits on that board not to turn on the screen. As I mentioned, the VOUT for an adjustable regulator should be the voltage on the ADJ pin + 1.25V.

      That is the correct part.

      If you desolder it, you can verify it is bad.

      1) Put 2 AA batteries in series for a total of 3V DC.

      2) Connect the AA positive terminal to pin 2 (VIN).

      3) Connect the AA negative terminal to pin 3 (GND).

      4) Put your multimeter red probe on pin 4 (VOUT) and black probe on pin 3 (GND).

      5) If it is working correctly, pin 4 should read 1.25V DC because your ADJ is 0.0V.

      6) In this post, I show how to test a 3.3V fixed regulator.

      https://www.badcaps.net/forum/showpo...22&postcount=7

      7) Budm beat me to it while I was editing, re-editing, etc.
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      Comment

      • retiredcaps
        Badcaps Legend
        • Apr 2010
        • 9271

        #23
        Re: Samsung LNT4069FX/XAA no picture with sound

        Originally posted by budm
        BTW, I looked at the formula for calculating the output voltage on the spec sheet, it looks wrong
        That is something I would have never figured out.

        IC107 is an adjustable regulator since it has 5 pins, the fixed regulator per spec sheet will only have 3pins, so retiredcaps is correct, the output of pin 4 is wrong, too low, it should be around 2.5V
        Funny, I was just looking back at a monitor that has been sitting in my basement for 2 years. I still haven't figured out what is wrong with it, but I learned all about voltage regulators from PlainBill.

        https://www.badcaps.net/forum/showthread.php?t=10228
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        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.

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        Comment

        • ceconomon
          Senior Member
          • Oct 2011
          • 67
          • USA

          #24
          Re: Samsung LNT4069FX/XAA no picture with sound

          Does anyone have tips for removing the regulator?

          I used Chip Quik to desolder the pins. I can't get the base off the board. Are these glued or soldered on to the board?

          Comment

          • retiredcaps
            Badcaps Legend
            • Apr 2010
            • 9271

            #25
            Re: Samsung LNT4069FX/XAA no picture with sound

            Originally posted by ceconomon
            Does anyone have tips for removing the regulator?
            In post #22, point #6, I talk about how I do. Having a 3.2mm chisel tip also helps.
            Last edited by retiredcaps; 07-11-2012, 10:01 PM.
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            Comment

            • ceconomon
              Senior Member
              • Oct 2011
              • 67
              • USA

              #26
              Re: Samsung LNT4069FX/XAA no picture with sound

              I replaced the regulator today and unfortunately it did not resolve the problem.

              I took the following measurements with the replacement regulator installed. They don't appear to be any different from the the previous measurements.

              location -IC102 FRC board
              37302WU
              0735
              pin 1= 3.432
              pin 2= 3.431
              pin 3= 0.0
              pin 4= 2.478
              pin 5= 1.241


              location -IC107 FRC board - part was replaced
              37302WU
              1105
              pin 1= 3.437
              pin 2= 3.436
              pin 3= 0.0
              pin 4= 1.837
              pin 5= 1.264

              Do we have any more ideas on this one?

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #27
                Re: Samsung LNT4069FX/XAA no picture with sound

                Does the regulator get hot? (too hot to touch?)
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • ceconomon
                  Senior Member
                  • Oct 2011
                  • 67
                  • USA

                  #28
                  Re: Samsung LNT4069FX/XAA no picture with sound

                  The regulator is cool to the touch.

                  Comment

                  • retiredcaps
                    Badcaps Legend
                    • Apr 2010
                    • 9271

                    #29
                    Re: Samsung LNT4069FX/XAA no picture with sound

                    Originally posted by ceconomon
                    I replaced the regulator today and unfortunately it did not resolve the problem.
                    I don't know if anyone does it, but I always test the old part and the new part out of circuit to verify things work properly.
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                    Comment

                    • retiredcaps
                      Badcaps Legend
                      • Apr 2010
                      • 9271

                      #30
                      Re: Samsung LNT4069FX/XAA no picture with sound

                      1) There are 4 caps around IC107. Which one or ones (using the positive leg) have continuity to pin 4?

                      2) Can we get a close up picture of that area (IC107)? Front and backside.
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                      Comment

                      • ceconomon
                        Senior Member
                        • Oct 2011
                        • 67
                        • USA

                        #31
                        Re: Samsung LNT4069FX/XAA no picture with sound

                        I setup the battery test on the old voltage regulator and I'm not seeing any voltage on pin 4.

                        C104 has continuity to pin 4 on the regulator.
                        Attached Files

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #32
                          Re: Samsung LNT4069FX/XAA no picture with sound

                          You need to connect the on off pin too.
                          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                          Comment

                          • momaka
                            master hoarder
                            • May 2008
                            • 12170
                            • Bulgaria

                            #33
                            Re: Samsung LNT4069FX/XAA no picture with sound

                            I'm not really an expert with linear regulators like budm and retiredcaps are, so I can't say if that regulator is bad or not. However, I was wondering if the problem could be possibly caused by something else. Particularly, have a look at this picture again on page 1:
                            https://www.badcaps.net/forum/attach...6&d=1341687191
                            On the lower right corner, there are a bunch of SMD ferrite beads that look very charred. Or perhaps that is dirt/flux - I can't tell for sure.

                            My suggestion would be to try and clean that part of the board with isopropyl alcohol and retake another picture of the area. Also, check all of the ferrite beads with your multimeter - those are the components labeled with BDxxx (where xxx is a number). Personally, I've never seen one go bad, but it should take just a few minutes so might as well do it. To test those ferrite beads, set your multimeter to measure resistance (if you're using a manual multimeter, set to the lowest resistance scale - usually 200 Ohms) and check the resistance across the bead - it should read very low Ohms or ideally zero ohms and not "1" on the left side of the screen or "OL".

                            Also, there's quite a bit of discoloration on the board from those linear voltage regulators. Just FYI, about 2 weeks ago I bought a TV on craigslist in "as-is" condition. TV would power but display lots of random colored pixels on the screen. As it warmed up, the random colored pixels would slowly disapear and the picture would go back to normal. I found the problem to be bad BGA joints on a RAM chip caused by excessive heat from nearby linear voltage regulators (they were actually right under the RAM chip, just on the other side of the board). Whoever designed that main board is either a moron or a planned obsolescence design genius.

                            With that said, I think your problem could also be cracked BGA joints. Looking at this picture,
                            https://www.badcaps.net/forum/attach...5&d=1341687191
                            it seems there are 3 BGA chips in the upper right corner of the board (one is under a small heat sink). If nothing seems to fix the board, you could try reflowing those BGA chips. Oven reflow method may not work due to all of the caps on the board, but hot air (mostly from the underside and then a bit on the top side) may work.

                            The last thing I can think of is if some of those caps next to those voltage regulators have gone bad due to the excessive heat. But for that you'll need to have an ESR meter to check them with.

                            For now, just try cleaning the board in that area I mentioned and see if those ferrite beads are good.
                            I hope this helps in some way.

                            Comment

                            • ceconomon
                              Senior Member
                              • Oct 2011
                              • 67
                              • USA

                              #34
                              Re: Samsung LNT4069FX/XAA no picture with sound

                              Originally posted by tom66
                              You need to connect the on off pin too.
                              I'm not understanding you. I assume you are refering to the testing of the voltage regulator.

                              Battery + =pin2
                              Battery - =pin3 (ground)
                              Measure voltage from pin4 to pin3(ground) to test

                              Where is the on/off pin?

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #35
                                Re: Samsung LNT4069FX/XAA no picture with sound

                                If you look at the spec of that 5-pin regulator IC, PIN1 is an ENABLE pin to turn the output ON/OFF. Please see the spec sheet.
                                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

                                • ceconomon
                                  Senior Member
                                  • Oct 2011
                                  • 67
                                  • USA

                                  #36
                                  Re: Samsung LNT4069FX/XAA no picture with sound

                                  Originally posted by budm
                                  If you look at the spec of that 5-pin regulator IC, PIN1 is an ENABLE pin to turn the output ON/OFF. Please see the spec sheet.
                                  The spec sheet did nothing for me at my current level of knowledge. What would I connect the enable pin to complete the circuit?

                                  Comment

                                  • ceconomon
                                    Senior Member
                                    • Oct 2011
                                    • 67
                                    • USA

                                    #37
                                    Re: Samsung LNT4069FX/XAA no picture with sound

                                    I cleaned the back of the mainboard with alcohol. I've examined that area throughly with a magnifying glass and I can't determine the source of that mess. It looks like flux to me. Here are the new pictures.

                                    All of the ferrite beads tested good.
                                    Attached Files

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA

                                      #38
                                      Re: Samsung LNT4069FX/XAA no picture with sound

                                      EN pin1 to pin2 Vin. Are the regulator you are checking has 5 pins?
                                      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

                                      • ceconomon
                                        Senior Member
                                        • Oct 2011
                                        • 67
                                        • USA

                                        #39
                                        Re: Samsung LNT4069FX/XAA no picture with sound

                                        Originally posted by budm
                                        EN pin1 to pin2 Vin. Are the regulator you are checking has 5 pins?
                                        The regulator does have 5 pins and the data sheet confirms pin1=EN and pin2=VIN.

                                        That explains why the measurements on pin1 and 2 were the same on my previous test.

                                        After connecting pin1 and pin2, I'm measuring 3 volts on pin4. That doesn't make sense to me. It was measuring lower than the input voltage before.

                                        Comment

                                        • budm
                                          Badcaps Legend
                                          • Feb 2010
                                          • 40746
                                          • USA

                                          #40
                                          Re: Samsung LNT4069FX/XAA no picture with sound

                                          When you test the adjustable regulator, you will need to attach two resistors, one will be between output pin and the ADJ pin, another one will be between the adj pin and ground.
                                          The output voltage will have to be calculated using the formula.
                                          The fixed regulator does not need the external resistors since they will be inside the regulator. The fixed regulator will have number such as 33 after the regulator P/N to indicate the output voltage, in this case, 33 means the regulator is a 3.3V regulator.
                                          What kind of P/N is on the regulator?
                                          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

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