Sharp LC-70SQ15 PWB DPS-206EP problem

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  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #21
    Re: Sharp LC-70SQ15 PWB DPS-206EP problem

    At this point, it looks like the Boost converter is working but the Q7202 is not getting the DIMOUT (pin 11) drive of the BD9488 to drive the Gate to turn that MOSFET on and off to allow the LED current to flow. Check the resistance between GND and the DIMOUT pin to see if it shows low resistance reading or not. You should also test R7299 (connected to pin 11) and also the resistor connected to the Gate of Q7202, also check Q7202 itself.
    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

    • rabitbay
      Member
      • Aug 2019
      • 20
      • BC

      #22
      Re: Sharp LC-70SQ15 PWB DPS-206EP problem

      Originally posted by budm
      At this point, it looks like the Boost converter is working but the Q7202 is not getting the DIMOUT (pin 11) drive of the BD9488 to drive the Gate to turn that MOSFET on and off to allow the LED current to flow. Check the resistance between GND and the DIMOUT pin to see if it shows low resistance reading or not. You should also test R7299 (connected to pin 11) and also the resistor connected to the Gate of Q7202, also check Q7202 itself.
      Between DIMOUT and GND got 12.5k
      The resistor to the gate R7231 labeled as 2.49k seem ok, with 2.47k

      I couldn't find the R7299 I'm assuming you are talking of the jumper resistance R7229, have 0 as labeled

      Some days ago I removed the MOSFET to test it out, and couldn't find any faults, but just to double check I removed it again, I've attached the readings. Also no continuity between gate and S on any direction
      Attached Files
      Last edited by rabitbay; 09-24-2019, 12:42 PM.

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #23
        Re: Sharp LC-70SQ15 PWB DPS-206EP problem

        "Also no continuity between gate and S on any direction"
        It is MOSFET, that is why.
        https://www.elprocus.com/mosfet-as-a...free-circuits/

        No Gate drive for the MOSFET may mean the IC is bad or something is locking out the drive output.
        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

        • rabitbay
          Member
          • Aug 2019
          • 20
          • BC

          #24
          Re: Sharp LC-70SQ15 PWB DPS-206EP problem

          Originally posted by budm
          "Also no continuity between gate and S on any direction"
          It is MOSFET, that is why.
          https://www.elprocus.com/mosfet-as-a...free-circuits/

          No Gate drive for the MOSFET may mean the IC is bad or something is locking out the drive output.
          Yeah!! After trying to test it on ON state, both of the MOSFET was not Closing, so Both MOSFET are OPEN ??
          I will replace them an tell you what happend

          Comment

          • rabitbay
            Member
            • Aug 2019
            • 20
            • BC

            #25
            Re: Sharp LC-70SQ15 PWB DPS-206EP problem

            Well, this is not going good, I did changed the MOSFETs and still is in black.

            Still have 0v on DIMOUT not even a peak when I plug to AC, now I'm really lost.

            Ok but now something weird happened, when I connect my positive probe to
            PWM1 or PWM2 the LED's turned ON, well that's a progress I guess, but I thought that the driver DIMOUT was controlled by ADIMM, and Why is this happening, I've attached some pictures, you can see the backlight through the holes
            Can I hook up everything to test it out?
            Attached Files

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #26
              Re: Sharp LC-70SQ15 PWB DPS-206EP problem

              The Backligts can be dimmed by ADIM (Analog dimming control by varying the DC level), the PWM1 and 2 are for the Pulse Width Modulation dimming scheme by varying the pulse width, it will be setup for one or the other, not both. Most TV use PWM Dimming control. You board uses the word DIMMER and you do have >3V that DIMMER pin of the PD pin, so this one may be using Analog dimmer setup.
              MOSFET Q7201 is for boost converter circuit as explained before and it is OK otherwise you will not have that Boosted Voltage so I do not understand why you replace that one.
              Last edited by budm; 09-24-2019, 09:18 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

              • nomoresonys
                Badcaps Legend
                • Jan 2013
                • 12084
                • U.S.

                #27
                Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                Originally posted by rabitbay
                Well, this is not going good, I did changed the MOSFETs and still is in black.

                Still have 0v on DIMOUT not even a peak when I plug to AC, now I'm really lost.

                Ok but now something weird happened, when I connect my positive probe to
                PWM1 or PWM2 the LED's turned ON, well that's a progress I guess, but I thought that the driver DIMOUT was controlled by ADIMM, and Why is this happening, I've attached some pictures, you can see the backlight through the holes
                Can I hook up everything to test it out?
                Check bottom of board for any bad/cold solder joints.

                Comment

                • rabitbay
                  Member
                  • Aug 2019
                  • 20
                  • BC

                  #28
                  Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                  Originally posted by budm
                  The Backligts can be dimmed by ADIM (Analog dimming control by varying the DC level), the PWM1 and 2 are for the Pulse Width Modulation dimming scheme by varying the pulse width, it will be setup for one or the other, not both. Most TV use PWM Dimming control. You board uses the word DIMMER and you do have >3V that DIMMER pin of the PD pin, so this one may be using Analog dimmer setup.
                  Yes I understand that

                  Originally posted by budm
                  MOSFET Q7201 is for boost converter circuit as explained before and it is OK otherwise you will not have that Boosted Voltage so I do not understand why you replace that one.
                  Just in case

                  Comment

                  • rabitbay
                    Member
                    • Aug 2019
                    • 20
                    • BC

                    #29
                    Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                    Originally posted by nomoresonys
                    Check bottom of board for any bad/cold solder joints.
                    It reads 45v AC from HOT to COLD just to verify, is that normal?
                    Last edited by rabitbay; 09-25-2019, 09:20 AM.

                    Comment

                    • Davi.p
                      Badcaps Legend
                      • Sep 2009
                      • 4271
                      • Italy - Milan

                      #30
                      Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                      Hi, you have changed Q7201, but if it was failed also the Rs will be failed, that one connected to pin 11 CS of the IC and to the source of Q7201.

                      Comment

                      • rabitbay
                        Member
                        • Aug 2019
                        • 20
                        • BC

                        #31
                        Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                        Originally posted by Davi.p
                        Hi, you have changed Q7201, but if it was failed also the Rs will be failed, that one connected to pin 11 CS of the IC and to the source of Q7201.

                        I agree with you, I appreciate your answer, do you know some technique to check if it has the right values?, for Rs just by reading the number, but in the other components

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #32
                          Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                          Q7201 is for the boost converter and you DO HAVE 268V per your post #17 LED boosted Voltage, PWM Controlled Q7202 is the one that is not getting the drive to turn it on.
                          So are you saying now that you no longer have LED boosted Voltage?
                          Last edited by budm; 09-28-2019, 02:34 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

                          • Davi.p
                            Badcaps Legend
                            • Sep 2009
                            • 4271
                            • Italy - Milan

                            #33
                            Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                            Rs is less than 1ohm, don't know how much. Yes i have forgot you have a boosted tension for an instant, have you tested the power diode? It is maybe that one in TO220..

                            Comment

                            • rabitbay
                              Member
                              • Aug 2019
                              • 20
                              • BC

                              #34
                              Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                              Originally posted by Davi.p
                              Rs is less than 1ohm, don't know how much. Yes i have forgot you have a boosted tension for an instant, have you tested the power diode? It is maybe that one in TO220..
                              I'm thinking to make a video, so I can show you better, because I'm starting to think that I'm misunderstanding some points or maybe or maybe I am misjudging some testings.

                              So some points I'm gonna cover is:

                              Voltage tests on LED pins
                              Voltage peak on LED pins when tv is turned on
                              Returned voltage on each strip
                              PMW effect of multimeter probe when testing pin 5/6 on LED driver

                              Comment

                              • rabitbay
                                Member
                                • Aug 2019
                                • 20
                                • BC

                                #35
                                Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                                After trying to make a small simulation of the OpAmp IC7202, the simulator gave me the same values on pin 3 and 2, but on reality I have very difrent values,


                                PD: I didn't find the TO220
                                Attached Files

                                Comment

                                • Davi.p
                                  Badcaps Legend
                                  • Sep 2009
                                  • 4271
                                  • Italy - Milan

                                  #36
                                  Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                                  I mean D7216 if i see well..

                                  Comment

                                  • rabitbay
                                    Member
                                    • Aug 2019
                                    • 20
                                    • BC

                                    #37
                                    Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                                    Originally posted by Davi.p
                                    I mean D7216 if i see well..
                                    I remove it to check it out, and it's ok, no short or open on any of both diods

                                    Comment

                                    • Davi.p
                                      Badcaps Legend
                                      • Sep 2009
                                      • 4271
                                      • Italy - Milan

                                      #38
                                      Re: Sharp LC-70SQ15 PWB DPS-206EP problem

                                      there was no need to remove it..

                                      Comment

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