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    #1

    HP no backlight

    This is a 19 " HP which powers on OK but the backlights will not light. I tested these lights and they test OK I replaced all the cap on the power board with same results. I am looking at retiredcaps sticky and am thinking that it may be a transistor but I am rather intimidated by these because I am not sure how to identify them for example how can one determine the start/stop transistor? The signalling transistors? etc. This board has quite a number components with the Q designation but look different. Some has E,C,B and some has S,G,D and than there are some with 8 contacts like the 2 (P607 BD5A18)
    Attached Files
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    #2
    Re: HP no backlight

    Originally posted by davg View Post
    (P607 BD5A18)
    P607 datasheet

    http://pdf1.alldatasheet.com/datashe...D/AOP607L.html

    Measure to see if S1-G1, S1-D1 and D1-G1 are shorted. Do the same for the "2s" and report your readings.
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      #3
      Re: HP no backlight

      Thanks retiredcaps assuming pin 1 is indicated with a dimple the readings are as follows
      Q 104
      S1-G1-30 m ohms
      S1- D1- 4 M Ohms
      G1-D1- 0L
      S2-G2-69 M OHMS
      S2-D2-0L
      G2-D2-0L
      Q105
      S1-G1-29 M Ohm
      S1-D1- 20 M Ohm
      G1-D1- 0L
      S2-G2-38 M Ohm
      S2- D2-0L
      G2-D2-0L
      where I get a reading the reading is continually decreasing?
      Last edited by davg; 11-02-2012, 04:01 PM.

      Comment

        #4
        Re: HP no backlight

        None of those mosfets are shorted.

        On the connector to the main/logic board (which is cut off in the picture), is there a legend? If yes, is there a pin that says BL_ON or something. The main board generates the BL_ON and it should be > 2.0V DC.
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          #5
          Re: HP no backlight

          Yes there is as follows BRL ON_OFF, +5 volts, +5 volts, GND, GND, GND, +12 Volts. The voltages on these pins read 1.57v, 0v, 5.22v, 5.22v, 0v, 0v, 0v, 12.24v. You say non of these mosfets are shorted!! what kind of readings would I get if they were? (just learning)

          Comment

            #6
            Re: HP no backlight

            What is the model number of this HP? Can you zoom out a little bit so I can see the whole board, both sides? By the way, do you see the lights even flash on at all?
            Last edited by budm; 11-02-2012, 07:58 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

              #7
              Re: HP no backlight

              Originally posted by davg View Post
              Yes there is as follows BRL ON_OFF, +5 volts, +5 volts, GND, GND, GND, +12 Volts. The voltages on these pins read 1.57v, 0v, 5.22v, 5.22v, 0v, 0v, 0v, 12.24v. You say non of these mosfets are shorted!! what kind of readings would I get if they were? (just learning)
              BRL = 1.57V
              ON_OFF = 0V

              I'm not 100% sure if BRL is backlight. The "R" is confusing me. Additionally, ON_OFF could be the backlight on/off command.

              I define a short as anything less than 30 ohms. AFAIK, there is no industry agreed upon value.
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              Comment

                #8
                Re: HP no backlight

                The model # is HP-VS17 I will upload pictures in the morning. I have it apart now but I can't be sure if it flashes or not but if it does its quicker than the eye. When plugged in the blue power light comes on than goes to amber. I don;t see any flash of the backlights but I can see the image with a bright light.

                Comment

                  #9
                  Re: HP no backlight

                  Originally posted by retiredcaps View Post
                  BRL = 1.57V
                  ON_OFF = 0V

                  I'm not 100% sure if BRL is backlight. The "R" is confusing me. Additionally, ON_OFF could be the backlight on/off command.

                  I define a short as anything less than 30 ohms. AFAIK, there is no industry agreed upon value.
                  On closer look that BRL is actually BRI ON_OFF if that makes any sense??. So is that 1.57v within tolerances for the ON pin? Is the 0V correct for the OFF pin? All others seem OK

                  Comment

                    #10
                    Re: HP no backlight

                    BRI is brightness. ON_OFF, then, is your backlight on/off. It is 0V, then the main/logic board is not generating it.

                    Check the voltage regulators on the main/logic board. My sig file has a how to guide.
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                    Please do not post inline and offsite as they slow down the loading of pages.

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                    Comment

                      #11
                      Re: HP no backlight

                      Post a picture of the main board as well.
                      --- begin sig file ---

                      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.

                      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.

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                      Comment

                        #12
                        Re: HP no backlight

                        Since the LED is AMBER, then that make sense why the ON_OFF is 0V. If the main board does not sense the video signal from the PC, it will turn off the inverter and the power to the LCD T-CON board. So check the regulators on the main board as suggested by retiredcaps.
                        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

                          #13
                          Re: HP no backlight

                          Originally posted by budm View Post
                          If the main board does not sense the video signal from the PC, it will turn off the inverter and the power to the LCD T-CON board.
                          Connecting a working source (PC) to the lcd monitor is always recommended.
                          --- begin sig file ---

                          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.

                          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

                            #14
                            Re: HP no backlight

                            Here are the pictures that budm requested and with the unit attached to a pc the blue light stays blue but there is no flash of the backlights at all. I am hearing a humming sound on the power board when everything is hooked up. Is this normal? I have to do some reading before I start testing the regulators.
                            Attached Files

                            Comment

                              #15
                              Re: HP no backlight

                              The readings on the two regulators I304 and I305 are as follows:
                              I304
                              AIC line 1
                              1084-33PM line 2
                              328GC line 3
                              pin #1- 0V
                              pin#2- 3.29v
                              pin#3- 4.9v

                              I305
                              1117 line#1
                              -18PE line#2
                              91OCT line#3
                              pin #1 - 0v
                              pin#2 - 1.79v
                              pin#3 - 3.29
                              pins numbered left to right with long pad north

                              Comment

                                #16
                                Re: HP no backlight

                                I noticed that the caps on this board are CapXon even though they look OK could these cause the problem?

                                Comment

                                  #17
                                  Re: HP no backlight

                                  Your voltage regulator readings look good. Here's what I think the problem is:

                                  On your photo of the logic board, what is the part number for I308? It's the 3 terminal device right above the 10-wire wiring harness. If it's something like MAX809/810, then it's a reset controller. If yes, with power off, use your soldering iron to lift the VCC and RESET pins off the circuit board. Power up the monitor to see if you get an image. Note: failure of this controller has caused the same problem on various acer models.

                                  Comment

                                    #18
                                    Re: HP no backlight

                                    Thanks jetadm123 The best I can tell the markings on that I308 is ARNQ4 but it is so small it's a job to tell.?

                                    Comment

                                      #19
                                      Re: HP no backlight

                                      So when the LED turns blue with connection to running PC, do you now get >3VDC at the ON/OFF PIN? If you do, then we need to go back and troubleshoot the inverter circuits.
                                      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

                                        #20
                                        Re: HP no backlight

                                        Thanks budm when connected to running pc I am reading 2.32v 3.24v 5.12v 5.13v 0v 0v 0v 12.24v on that 8 pin connector marked BRI ON-OFF, 5V, 5V, GRN, GRN, GRN, 12V. When the light turns amber the 3.24v drops to 0v?
                                        Last edited by davg; 11-04-2012, 06:52 AM.

                                        Comment

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