Hisense 32K20DW missing LED voltages and 6 blinks

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  • steves7839
    Badcaps Veteran
    • Nov 2014
    • 200
    • USA

    #1

    Hisense 32K20DW missing LED voltages and 6 blinks

    Hi All!
    I,m troubleshooting a Hisense 32K20DW that won't turn on.
    5VSTB is present when the set is off. When turned on, 12V are present, SW >4V. No sound, video or backlight. The STB LED blinks 6 times, then goes off.

    Here are the pins and voltages at the 10-pin connection to the Main Bd:
    ON:
    STBY 0V
    12V 12V
    GND 0
    16V 0V
    SW 4V

    The same pins when OFF (the standby LED on the bezel is red):
    STBY 5V
    12V 12V
    GND 0V
    16V 0V
    SW 4V

    Strangely enough, the largest cap C829 reads both 178VDC and 368VAC across it's leads with my VOM.
    Other caps on the PSB and their on voltages follow:
    C827,828 45V
    C855,861,862 12V
    C717 by LED pwr 0V

    I suspect power supply, would greatly appreciate knowing if these factors point to any specific component.
    Attached Files
    Last edited by steves7839; 04-30-2016, 04:26 PM.
  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8102
    • Canada

    #2
    Re: Hisense 32K20DW missing LED voltages and 6 blinks

    The large cap reading 2 different voltages is normal. The lower voltage is rectified mains, the higher voltage is boosted PFC voltage. From what you are saying, the main board is turning the PSU on, but the 16V rail is dead. So either there is something wrong with the PSU on the 16V rail or the main board is dragging it down. You can try forcing the PSU on without the main board attached and check if the 16V reappear. Or try to take the 16V pin out of the connector?

    Comment

    • steves7839
      Badcaps Veteran
      • Nov 2014
      • 200
      • USA

      #3
      Re: Hisense 32K20DW missing LED voltages and 6 blinks

      I separated the PS from the Main Board and jumpered 12V to ST on XT802 with a 1.2K resistor (since STB was not present, it seems to be made on the MainBd.)
      Still no 16V.
      The attached photo shows the rear side of the PSB. V712 and V713 look like voltage regulators. One has 46VDC on the large solder tab, but nothing on pins 1 or 3. The other has no DCV on any pin or tab.

      I'm digging through the attached Hisense schematics elsewhere on the web site. If anyone has a link to RSAG7.820.5338 PSB and RSAG7.820.5555 Main Board schematics please point me there!

      Thanks for reading!
      Attached Files

      Comment

      • CapLeaker
        Leaking Member
        • Dec 2014
        • 8102
        • Canada

        #4
        Re: Hisense 32K20DW missing LED voltages and 6 blinks

        I was able to look at that PSU over at SJ on the front and back. Looks like the 16V is not installed on yours. The cap C853 and diode VD819 are not installed on your board. So you can't have any 16V.

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Hisense 32K20DW missing LED voltages and 6 blinks

          What happen if you disconnect the LED connector XP804, will TV boot up OK?
          What dcv do you have between the legs of cap C717?
          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

          • steves7839
            Badcaps Veteran
            • Nov 2014
            • 200
            • USA

            #6
            Re: Hisense 32K20DW missing LED voltages and 6 blinks

            "What dcv do you have between the legs of cap C717?"
            None. 0VDC. Even with the XP804 LED power disconnected, I measure no voltage at those pins.

            I have 45VDC across C827 and C828. Seems like higher voltages would have to come from here.
            Last edited by steves7839; 05-05-2016, 04:55 PM. Reason: add detail

            Comment

            • dick_barton
              Badcaps Legend
              • Aug 2015
              • 6642
              • Wales

              #7
              Re: Hisense 32K20DW missing LED voltages and 6 blinks

              It may be worth checking VD705 & Q701.
              Willing to help but I'm no expert.

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: Hisense 32K20DW missing LED voltages and 6 blinks

                C717 is the filter cap for the LED power supply boost converter output so the power supply is dead at this point even though you do have 'SW 4V' to turn on that LED power supply section, so more in-depth troubleshooting of the power supply board will be required to get down to the component level.
                Boost converter has L701, Q701, D705, and there should be LED controller for the LED power supply.
                Last edited by budm; 05-05-2016, 05:19 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

                • steves7839
                  Badcaps Veteran
                  • Nov 2014
                  • 200
                  • USA

                  #9
                  Re: Hisense 32K20DW missing LED voltages and 6 blinks

                  Q701 is the tab for V712 which is at 45VDC and appears at LN on XP804. C715 and C716 in parallel appear to couple something to LP, which reads 0VDC. VD705 has good forward drop, .45 in Diode test. Looks like I should pull C715&C716 for out of circuit test....?

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Hisense 32K20DW missing LED voltages and 6 blinks

                    can we see the straight shot pictures of the whole bottom side of the board? There should be an IC controller for the LED backlights.
                    Right now you have 45V input to the boost converter but no boosted output Voltage for the LEDs.
                    Last edited by budm; 05-05-2016, 11:37 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

                    • CapLeaker
                      Leaking Member
                      • Dec 2014
                      • 8102
                      • Canada

                      #11
                      Re: Hisense 32K20DW missing LED voltages and 6 blinks

                      Originally posted by budm
                      can we see the straight shot pictures of the whole bottom side of the board? There should be an IC controller for the LED backlights.
                      Right now you have 45V input to the boost converter but no boosted output Voltage for the LEDs.
                      courtesy to SJ
                      http://assets.shopjimmy.com/media/ca...180-bottom.jpg

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Hisense 32K20DW missing LED voltages and 6 blinks

                        IC N803 is the LED Backlights controller.
                        MOSFET V713 is the PWM controlled for the LED string (Cathode) return side.
                        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

                        • steves7839
                          Badcaps Veteran
                          • Nov 2014
                          • 200
                          • USA

                          #13
                          Re: Hisense 32K20DW missing LED voltages and 6 blinks

                          V712 has 40.5VDC at the tab and at XP804 pin LN. V713 shows no DCV at any point. It's tab is tied to XP804 pin LP.
                          What are the key pins to probe around N803, the controller IC?

                          On the photo of VD811 and V807 on the top side of the PSB, what is the significance of 180 VDC on the center lead, which appears to be a diode?

                          What range of voltage should I be looking for on the return side of the LED supply?
                          Attached Files
                          Last edited by steves7839; 05-06-2016, 06:18 PM. Reason: add detail

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #14
                            Re: Hisense 32K20DW missing LED voltages and 6 blinks

                            Originally posted by steves7839
                            V712 has 40.5VDC at the tab and at XP804 pin LN. V713 shows no DCV at any point. It's tab is tied to XP804 pin LP.
                            What are the key pins to probe around N803, the controller IC?

                            On the photo of VD811 and V807 on the top side of the PSB, what is the significance of 180 VDC on the center lead, which appears to be a diode?

                            What range of voltage should I be looking for on the return side of the LED supply?
                            I think you have measurement error, the LP pin of the xp804 connector is the boosted output pin to the Anode of the LED string, this LP pin is connected to the Cathode of the diode VD705 and it is also connected to the + pin of the C717 (filter cap for the booster circuit which you said it shows 0 VDC between the two legs of the cap), the Anode pin of the Diode VD705 is connected to the output end of the inductor L814, input end of the inductor L814 is connected to the big tab of MOSFET V712 which you indicated that you have 40VDC on the tab, so it must be measurement error to have 0 VDC on the capacitor C717 unless the inductor or the diode has open circuit. You need to verify that again, I am sure that you should also have 40VDC at the LP pin of connector XP804.
                            If you trace out the connection at the bottom side you will see what I have describe how the circuits are connected together.
                            Right now 40V is just an input Voltage to the booster circuit and it is not being booster high enough to light up the LED, I expect it to be around 70~80V range.
                            We also need the P/N of that LED controller IC.
                            BTW, the LN pin is the Cathode return side of the LED string.

                            Pictures provided by shojimmy:
                            http://www.shopjimmy.com/hisense-167...upply-unit.htm
                            Attached Files
                            Last edited by budm; 05-06-2016, 07:55 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

                            • steves7839
                              Badcaps Veteran
                              • Nov 2014
                              • 200
                              • USA

                              #15
                              Re: Hisense 32K20DW missing LED voltages and 6 blinks

                              V712 is shorted pin to pin. I confirmed this by raising one leg. MDD1904 is printed on the FET. It's a good part number so I'm going to order a couple.
                              The 14-pin voltage controller N803 has a number BB0533GP.
                              Attached Files
                              Last edited by steves7839; 05-07-2016, 10:08 PM. Reason: add detail

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Hisense 32K20DW missing LED voltages and 6 blinks

                                The picture you show: https://www.badcaps.net/forum/attach...4&d=1462678576 is for V713 (MDD1904) which is for the Cathode for the LED string return.
                                <1 Ohm reading between pin ? and pin?
                                Last edited by budm; 05-07-2016, 10:41 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

                                • steves7839
                                  Badcaps Veteran
                                  • Nov 2014
                                  • 200
                                  • USA

                                  #17
                                  Re: Hisense 32K20DW missing LED voltages and 6 blinks

                                  I measured 0.2 ohms or so between S-G, G-D(tab) and S-D, even after desoldering and lifting the S leg.
                                  Attached Files

                                  Comment

                                  • steves7839
                                    Badcaps Veteran
                                    • Nov 2014
                                    • 200
                                    • USA

                                    #18
                                    Re: Hisense 32K20DW missing LED voltages and 6 blinks

                                    Replaced V712 with a new FET. Set is back to original symptom: It powers on with 6 blinks of the STBY LED which then goes off. No sound or backlight appears. The voltage across XP804 LED power: 84VDC with LED string disconnected, return side rises to 24VDC when string is connected. Is this consistent with a bad LED string?

                                    The Main board produces SW-ON 3V, 12V to the T-CON bd, 1.5, 3.2V and 5V. No response to flexing or heating.

                                    Comment

                                    • dick_barton
                                      Badcaps Legend
                                      • Aug 2015
                                      • 6642
                                      • Wales

                                      #19
                                      Re: Hisense 32K20DW missing LED voltages and 6 blinks

                                      So what voltage do you have at the LED connector with the leds disconnected?

                                      Edit:
                                      Ignore since you already say above which I missed.

                                      But do the backlights flash no matter how breifly at all when you power up?
                                      Last edited by dick_barton; 05-15-2016, 12:27 PM.
                                      Willing to help but I'm no expert.

                                      Comment

                                      • dick_barton
                                        Badcaps Legend
                                        • Aug 2015
                                        • 6642
                                        • Wales

                                        #20
                                        Re: Hisense 32K20DW missing LED voltages and 6 blinks

                                        I believe the led voltage should be 150V at 400mA as written on the power supply board.
                                        Willing to help but I'm no expert.

                                        Comment

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