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Help, I need to identify burnt chip.

Discussion in 'Troubleshooting and Repair' started by Revol, Jan 27, 2017.

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  1. Revol

    Revol

    3
    0
    Jan 27, 2017
    I have a 12vdc 12" Led Monitor model #YJ121LED that had a blown capacitor (changed), but the led backlight board has a 6 pin chip on it that had the lettering burned off it. If I can identify the chip I can change it out. The board has XQY-LED0103 v3 on it if that helps. I am told that this is a 6 pin SOIC chip. All help greatly appreciated. Thank you.
     

    Attached Files:

  2. shrtrnd

    shrtrnd

    3,827
    520
    Jan 15, 2010
    Try Googleing the model number to see if you can find a free (or cheap) schematic so you can identify the burned chip. Maybe even a schematic on the manufacturer's website(?)
     
  3. Revol

    Revol

    3
    0
    Jan 27, 2017
    Thanks Shrtrnd, tried that, even found the board with a picture, not exact components but very close, no luck with drawings also. Problem here is 12" monitor is no longer available in this metal case "industrial" version. I have found plastic case versions that I believe to be exact same but no communication back to China as it is holiday there.

    Anyway, from my research this board takes 12vdc and converts it to run the backlighting for the screen. I am assuming the yellow wire is the signal to turn the lights on or off but not sure. Perhaps someone with knowledge of these things can explain what it does or what is happening so I can identify the chip I need from what it needs to do! Black/white wires goes to the led backlights.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If the backlighting ccfl or led?
     
  5. Revol

    Revol

    3
    0
    Jan 27, 2017
    Specs say LED backlighting.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,500
    2,840
    Jan 21, 2010
    I have seen many (and used one) third party ccfl driver to replace a failed driver.

    Perhaps there are replacement LED drivers for monitors.

    This is probably just some form of constant current driver, either buck or boost. However this, the compliance voltage and the required current are unknown to me.

    However, LEDs are easier to investigate than ccfl! If you have access to a current limited variable voltage power supply then you could investigate the required voltage and the current which gives the subjectively correct brightness.
     
  7. 73's de Edd

    73's de Edd

    3,230
    1,351
    Aug 21, 2015
    Sir Revol . . . . . . . . . .

    On small 12 in units like yours and on down to tablet sizes and digital display picture frames..
    The PT4115 has been extensively used as a buck converter and LED backlight controller
    Take this data sheet and initially note on page 2, that your unit is being in the left SOT89-5 casing profile.
    Its sort of a wierd duck , IF you can' t see the back heat sinked side, without the unit being fully pulled off the PC board.
    I refer to the page 2 where you see the pin #2 being its ground. What you wouldn' t know otherwise, is that is ALSO the SAME connection as the exposed tab that is marked up at the top of the chip.

    I submit this pic of the other side for your examination.

    PT4115 . . . Buck Supply and LED Brite Controller . . . . . . Heat sinked side

    PT4115 chip.jpg

    Now take out your ohmmeter . . .lowest scale . . . and just measure from pin 2 bottom up to that tab to confirm that connection.

    Next go to the end of the data sheet and compare some of their design options to what components that you are finding on the board.

    Looking at your connections on your pic, its a given to expect the RED and BLACK to be the power connections of the RED plug.
    That is leaving the YELLOW to be the BRITE input info.
    ( In a foil path connection rundown, just see if you dont end up seeing YELLOW wire ending up being either directly or indirectly connected to pin # 3 DIM function.)
    At the bottom, on the WHITE plug . . . . would be the power outputting to the backlight LEDs.


    Your Pee Dee Eff Da-Da sheet hot link for the PT4115

    https://people.xiph.org/~xiphmont/thinkpad/PT4115E.pdf

    One of several sources for the chip:

    https://www.aliexpress.com/item/PT4...32703389843.html?spm=2114.40010308.4.2.64NAcy

    If all fails . . . .here is a Dual Driver . . .in case you have to buy a complete unit
    ( You could clip the power input foil leading into one unit to disable it . . . . if the other unit then being used, happens to fail , revert to enabling the other virgin unit, just waiting to be used.)

    https://www.aliexpress.com/item-img...81824.html?spm=2114.10010108.1000017.2.3tkxsY



    Thassssit . . . . . .


    73's de Edd
     
    Last edited by a moderator: Jan 28, 2017
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