Samsung LN-T3242H power supply

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  • zachn
    Member
    • Nov 2010
    • 23
    #1

    Samsung LN-T3242H power supply

    Hi,
    I have a samsung LN-T3242H that keeps blowing the fuse on the power supply board. the power supply board is model BN44-00192A. nothing on the board has any visible sign of damage. does anyone have an idea of where to start troubleshooting? Thanks!
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    • retiredcaps
      Badcaps Legend
      • Apr 2010
      • 9271
      #2
      Re: Samsung LN-T3242H power supply

      Originally posted by zachn
      Hi,
      nothing on the board has any visible sign of damage. does anyone have an idea of where to start troubleshooting?
      1) What is that stuff on the VX801 component?

      2) Check BD801S for shorts using ohms. Number the pins 1-4. With power off and lcd unplugged check 1-2, 1-3, 1-4, 2-3, 2-4, and 3-4. If any reading is less than 30 ohms, it suggests a shorted bridge rectifier.
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        Comment

        • zachn
          Member
          • Nov 2010
          • 23
          #3
          Re: Samsung LN-T3242H power supply

          thanks for the reply!

          1. that is some glue on VX801, i had swapped that part with a know good board to see if anything changed.

          2. i will test the rectifier and post my findings! thanks

            Comment

            • zachn
              Member
              • Nov 2010
              • 23
              #4
              Re: Samsung LN-T3242H power supply

              should i remove the rectifier from the board for testing?

                Comment

                • retiredcaps
                  Badcaps Legend
                  • Apr 2010
                  • 9271
                  #5
                  Re: Samsung LN-T3242H power supply

                  Originally posted by zachn
                  should i remove the rectifier from the board for testing?
                  You can test it "in circuit". If the readings are under 30 ohms, then desolder to verify.
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                    Comment

                    • Hobby 1
                      Senior Member
                      • Mar 2010
                      • 86
                      #6
                      Re: Samsung LN-T3242H power supply

                      Check the FETs and replace the caps. I worked on one of these a few months ago and the caps were splitting at the top.

                        Comment

                        • zachn
                          Member
                          • Nov 2010
                          • 23
                          #7
                          Re: Samsung LN-T3242H power supply

                          I tested the rectifier and there was a short between the 1-4 pins. I removed the part and tested again but it tested good. the short is somewhere else on the board. I suspect the part QHAD01216 is where the short is. How do I properly test that component?

                            Comment

                            • Hobby 1
                              Senior Member
                              • Mar 2010
                              • 86
                              #8
                              Re: Samsung LN-T3242H power supply

                              What is that part? (I don't have my maual handy). If it is a FET, remove it from the board and test again. Most of these switching supplies use a pair of FETs. If one is bad, so is the other.

                                Comment

                                • retiredcaps
                                  Badcaps Legend
                                  • Apr 2010
                                  • 9271
                                  #9
                                  Re: Samsung LN-T3242H power supply

                                  Originally posted by zachn
                                  I tested the rectifier and there was a short between the 1-4 pins. I removed the part and tested again but it tested good.
                                  What reading did you get out of circuit for pins 1-4?
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                                    Comment

                                    • zachn
                                      Member
                                      • Nov 2010
                                      • 23
                                      #10
                                      Re: Samsung LN-T3242H power supply

                                      pin 1-4 out of circuit was open. can you help me identify the part at RP819? it has 5W0.12ohmJ written on top.

                                        Comment

                                        • zachn
                                          Member
                                          • Nov 2010
                                          • 23
                                          #11
                                          Re: Samsung LN-T3242H power supply

                                          QHAD01216 is the small transformer, i took that off the board and tested for shorts and it looked good.

                                            Comment

                                            • retiredcaps
                                              Badcaps Legend
                                              • Apr 2010
                                              • 9271
                                              #12
                                              Re: Samsung LN-T3242H power supply

                                              Originally posted by zachn
                                              pin 1-4 out of circuit was open. can you help me identify the part at RP819? it has 5W0.12ohmJ written on top.
                                              I would say that bridge rectifiers, FETs, and diodes would be the most likely candidates causing the fuse to blow.

                                              The power FET is QP801S. The diodes are DT805, DT806, DP801, DP8?? (just left of QP801S).

                                              Check all these for shorts "in circuit". Again, if you get suspicious readings, remove and retest out of circuit.
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                                              Please do not post inline and offsite as they slow down the loading of pages.

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                                                Comment

                                                • PlainBill
                                                  Badcaps Legend
                                                  • Feb 2009
                                                  • 7034
                                                  • USA
                                                  #13
                                                  Re: Samsung LN-T3242H power supply

                                                  Originally posted by zachn
                                                  pin 1-4 out of circuit was open. can you help me identify the part at RP819? it has 5W0.12ohmJ written on top.
                                                  That sounds like a .12 ohm 5 Watt resistor. It's probably used to sense current through the main switching FET.

                                                  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

                                                    • Dgtech
                                                      E. Technician
                                                      • Apr 2009
                                                      • 1462
                                                      • Steeler
                                                      #14
                                                      Re: Samsung LN-T3242H power supply

                                                      You have an excellent clear picture of the component side of the board. Could you post the bottom side picture as well.
                                                      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                                        Comment

                                                        • retiredcaps
                                                          Badcaps Legend
                                                          • Apr 2010
                                                          • 9271
                                                          #15
                                                          Re: Samsung LN-T3242H power supply

                                                          Originally posted by zachn
                                                          pin 1-4 out of circuit was open.
                                                          If the bridge rectifier is still out of circuit, try tracing the "circuit path" from pin 1 to pin 4 using the soldering pads.

                                                          That might give a clue as to what is possibly shorted.
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                                                          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

                                                            • PlainBill
                                                              Badcaps Legend
                                                              • Feb 2009
                                                              • 7034
                                                              • USA
                                                              #16
                                                              Re: Samsung LN-T3242H power supply

                                                              Originally posted by retiredcaps
                                                              If the bridge rectifier is still out of circuit, try tracing the "circuit path" from pin 1 to pin 4 using the soldering pads.

                                                              That might give a clue as to what is possibly shorted.
                                                              Correct. Odds are it's the main SMPS FET.

                                                              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

                                                                • zachn
                                                                  Member
                                                                  • Nov 2010
                                                                  • 23
                                                                  #17
                                                                  Re: Samsung LN-T3242H power supply

                                                                  You guys are correct. the FET at QP801S is shorted, once i have a replacement installed i will post an update. Thanks!

                                                                    Comment

                                                                    • Hobby 1
                                                                      Senior Member
                                                                      • Mar 2010
                                                                      • 86
                                                                      #18
                                                                      Re: Samsung LN-T3242H power supply

                                                                      Don't forget to replace the caps also. They will fail soon also.

                                                                        Comment

                                                                        • zachn
                                                                          Member
                                                                          • Nov 2010
                                                                          • 23
                                                                          #19
                                                                          Re: Samsung LN-T3242H power supply

                                                                          Update

                                                                          I have replaced the FET at QP801S and the board is not shorting or popping the fuse anymore. However the tv does not fully power on, the standby light is on but doesnt power up. where would you recommend checking next?

                                                                            Comment

                                                                            • PlainBill
                                                                              Badcaps Legend
                                                                              • Feb 2009
                                                                              • 7034
                                                                              • USA
                                                                              #20
                                                                              Re: Samsung LN-T3242H power supply

                                                                              Originally posted by zachn
                                                                              Update

                                                                              I have replaced the FET at QP801S and the board is not shorting or popping the fuse anymore. However the tv does not fully power on, the standby light is on but doesnt power up. where would you recommend checking next?
                                                                              The power supply appears to have four output connectors. Typically these connectors have a legend that indicates the function of each pin. You would be looking for a pin labeled something like On , Power on, On/Off, etc. The voltage at that pin would be a good start.

                                                                              Of course, good pictures of the bottom of the supply would help, as would pictures of the legends.

                                                                              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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