HP no backlight

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  • davg
    replied
    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

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  • retiredcaps
    replied
    Re: HP no backlight

    Originally posted by budm
    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.

    Leave a comment:


  • budm
    replied
    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.

    Leave a comment:


  • retiredcaps
    replied
    Re: HP no backlight

    Post a picture of the main board as well.

    Leave a comment:


  • retiredcaps
    replied
    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.

    Leave a comment:


  • davg
    replied
    Re: HP no backlight

    Originally posted by retiredcaps
    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

    Leave a comment:


  • davg
    replied
    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.

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  • retiredcaps
    replied
    Re: HP no backlight

    Originally posted by davg
    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.

    Leave a comment:


  • budm
    replied
    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.

    Leave a comment:


  • davg
    replied
    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)

    Leave a comment:


  • retiredcaps
    replied
    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.

    Leave a comment:


  • davg
    replied
    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.

    Leave a comment:


  • retiredcaps
    replied
    Re: HP no backlight

    Originally posted by davg
    (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.

    Leave a comment:


  • davg
    started a topic HP no backlight

    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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