Sanyo DP37647 no backlight

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  • ishfish
    New Member
    • May 2013
    • 5
    • USA

    #1

    Sanyo DP37647 no backlight

    Hey all, I've got a Sanyo DP37647 with no backlight at all. LCD is working, just no backlight. I thought I was probably looking at a bad inverter board as I've done a few easy fixes with that before, but after reading a different thread about this and testing a little on the inverter board, I started to wonder if I was wrong.

    The first thing I did was test power to the inverter board from the power supply and I'm getting about 16V. My understanding is it should be 24V and that's where it ends for me.

    I don't know what else to test or what might be causing that. All components on all of my boards look okay, nothing looks burnt/blown out. The power boards are running close to $100 and my customer wants to know if there's any chance of me just fixing his old board (so do I) as a cheaper option if that is indeed the issue.

    Any guidance or help is greatly appreciated. Thanks!
  • johnboy1313
    Badcaps Legend
    • Nov 2012
    • 1959
    • USA

    #2
    Re: Sanyo DP37647 no backlight

    I can get you the service manual if you get me the chassis number off the tag on the bag. i.e DP37647-01, -02, -03, etc...

    Comment

    • ishfish
      New Member
      • May 2013
      • 5
      • USA

      #3
      Re: Sanyo DP37647 no backlight

      Looks like -00?
      Attached Files

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: Sanyo DP37647 no backlight

        http://www.toms-service-manuals.com/...&Search=Submit
        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

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Sanyo DP37647 no backlight

          Upload good clear picture of the boards, closed up picture of the inverter boards, especially around the connectors so we can see if there are any voltage labeling on them. We are looking for BL_ON (INV_ON or ON/OFF) signal, 24V pins on the inverter board,
          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

          • ishfish
            New Member
            • May 2013
            • 5
            • USA

            #6
            Re: Sanyo DP37647 no backlight

            I've attached an overview picture, the power board, connectors to the inverter, the inverter board, and the connectors from the power board. The 24V lines coming off of the power board are what I'm testing ~16V.
            Attached Files

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Sanyo DP37647 no backlight

              16V way too low. Check your multimeter is accurate by testing a fresh 1.5V battery.
              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

              • ishfish
                New Member
                • May 2013
                • 5
                • USA

                #8
                Re: Sanyo DP37647 no backlight

                Just tested my multimeter on 3 1.5V batteries and a 3.7V phone battery. It's reading correctly on all of them.

                The 16V reading had led me to suspect the power board in the first place, but I don't know enough about it to track down what might be wrong.

                Comment

                • Shane711
                  Badcaps Veteran
                  • Dec 2014
                  • 493
                  • USA

                  #9
                  Re: Sanyo DP37647 no backlight

                  I have a Sanyo DP37647 and I am having this exact problem. I am getting 5v on the standby, 8v on the 12v and 17v on the 24v. A wierd thing is when I have the main board disconnected I get 23.6v on the 24v and 11.6v on the 12v. Seems to me there might be a short on the main board but if not I guess it could be a bad cap on the Power board. Any ideas?

                  Comment

                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Sanyo DP37647 no backlight

                    What is the DCV measured between the two legs for the main DC filter cap when the TV is 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

                    • Shane711
                      Badcaps Veteran
                      • Dec 2014
                      • 493
                      • USA

                      #11
                      Re: Sanyo DP37647 no backlight

                      With everything plugged in I am getting 140v on, 146v off. With the main board disconnected I am getting 186v on. I am guessing this is way too low.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #12
                        Re: Sanyo DP37647 no backlight

                        AC 120VAC feeding the TV then you should have about 165~170VDC (120VAC x 1.414 = 169VDC), if you are only getting 146VDC (TV OFF) on the two legs of the main filter cap, I would say you probably have bad filter cap, since when TV is off you will have minimum load on that filter cap.
                        Any good clear pictures of YOUR board?
                        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

                        • Shane711
                          Badcaps Veteran
                          • Dec 2014
                          • 493
                          • USA

                          #13
                          Re: Sanyo DP37647 no backlight

                          OK, I took the power board and resoldered some connections, didn't see any broken spots. Used a different meter and got 211v on the cap. Might have been the use of a different(Better) meter. Still getting the voltage drop with the main board connected. Everything on the power board seems perfect. There is like 165v DC leaving the rectifier. I had another TV with the same problem and I changed all the caps and that fixed it so I think I will try that. I will start with the main cap.

                          On the main board I was testing the power fail circuit. The voltages looked good except for D1621 which is suppose to read 33v but is 5.75v. Not sure if this means a main board failure.
                          Attached Files

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #14
                            Re: Sanyo DP37647 no backlight

                            So now with all the boards connected, you are still getting steady 165VDC between the 2 legs of the main filter cap, right? So when the power switch is activate do you get >360VDC? If not, then the PFC Voltage booster circuit is not working. You do have PS-ON control signal form the main board feeding the power supply board, right?
                            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

                            • Shane711
                              Badcaps Veteran
                              • Dec 2014
                              • 493
                              • USA

                              #15
                              Re: Sanyo DP37647 no backlight

                              167.7v with the power off, I press power and it goes down to 163.00 and the backlights flash. I found 4 weak caps on the PS and changed them, not making any difference. I also changed out the main cap with one closer to the value of 150uf. Also it seems that at one time there was an arch from the PS to the frame, I included a picture. Sounds like it could be the PFC Voltage booster circuit as you describe, but I am not sure just what that is.
                              Attached Files

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Sanyo DP37647 no backlight

                                Originally posted by Shane711
                                167.7v with the power off, I press power and it goes down to 163.00 and the backlights flash. I found 4 weak caps on the PS and changed them, not making any difference. I also changed out the main cap with one closer to the value of 150uf. Also it seems that at one time there was an arch from the PS to the frame, I included a picture. Sounds like it could be the PFC Voltage booster circuit as you describe, but I am not sure just what that is.
                                So you are not getting boosted PFC Voltage.
                                Need the pictures that show the whole bottom side of the power supply board so we can try to identify the PFC section.
                                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

                                • Shane711
                                  Badcaps Veteran
                                  • Dec 2014
                                  • 493
                                  • USA

                                  #17
                                  Re: Sanyo DP37647 no backlight

                                  OK, there is a IC that I suspect, ICE 1PCS02. The weirdest thing is when I have it on and I am probing this IC it was cause the backlights to blink rapidly so it would seem this IC is at fault.
                                  Attached Files

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #18
                                    Re: Sanyo DP37647 no backlight

                                    ICE 1PCS02;' Are you talking IC800 DIP-8 through hole mounting IC?
                                    That is the PFC Controller IC. Are you getting steady DCV at the VCC pin and Gnd pin?
                                    Attached Files
                                    Last edited by budm; 08-07-2015, 02:25 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

                                    • Shane711
                                      Badcaps Veteran
                                      • Dec 2014
                                      • 493
                                      • USA

                                      #19
                                      Re: Sanyo DP37647 no backlight

                                      Yes, IC800 DIP-8 as you stated. I am getting a steady voltage at all the pins. I would think I would not get a reading at the ground pin but I do. Most of the voltages are around 33v. I am not at my shop now so I don't know the exact readings.

                                      Comment

                                      • budm
                                        Badcaps Legend
                                        • Feb 2010
                                        • 40746
                                        • USA

                                        #20
                                        Re: Sanyo DP37647 no backlight

                                        Originally posted by Shane711
                                        Yes, IC800 DIP-8 as you stated. I am getting a steady voltage at all the pins. I would think I would not get a reading at the ground pin but I do. Most of the voltages are around 33v. I am not at my shop now so I don't know the exact readings.
                                        You have to measure the DCV between the VCC pin and the Ground pin. Do not use the chassis as the GND ref. point for the meter because you are making Voltage measurement in the primary side of the circuit, not on the cold side (Isolated) of the circuit.

                                        "I would think I would not get a reading at the ground pin but I do. Most of the voltages are around 33v" That must be an error in measurement method.
                                        Last edited by budm; 08-07-2015, 04:36 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

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