Element LED No Backlight

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  • triplefour
    UN65TU700DF picture and sound but no backlight. BL tests ok but repl. PSU didnt fix!
    by triplefour
    this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
    i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
    unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
    according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even...
    09-13-2023, 10:43 PM
  • Comp_Pro
    No Backlight Macbook A1990 820-01041
    by Comp_Pro
    Hello all,

    Am trying to figure out this backlight issue with this A1990 Macbook Pro.

    Tests performed:

    There is no backlight even with a good screen.
    Backlight IC is receiving the correct support voltages.
    Fuse F8400 ok
    Current sense resistor R8400 ok
    Backlight IC is receiving 3.3V on enable pin.
    Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
    Backlight IC receiving 5V from PP5V_G3S
    Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
    I2C_BKLT_SCL and I2C_BKLT_SDA both measure...
    05-06-2024, 10:23 PM
  • cheebster
    iPad Pro 12.9 5th Gen Backlight Issue
    by cheebster
    Hello, got an iPad Pro A2378 12.9 5th gen with no backlight. Got another test unit without screen, tested the screen, still no backlight with the test unit.
    Figured out the backlight on the screen was bad, ordred a new backlight from mobilesentrix, *carefully replaced it* without damaging the lcd, oh well.
    Final result, issue is still there, the screen has no back lights. So i'm back to square one, with 3 hours less and 100$ out, issue still on the screen.
    The panel is still ok, i can see the apple in the middle of the screen when it kicks in, just no backlight.
    Anyone...
    05-20-2025, 09:17 AM
  • canadaboy25
    LG Flatron 24EN33TA No Backlight When Cold
    by canadaboy25
    Hi all,

    I've got an LG Flatron 24EN33TA with a backlight issue. The problem began with the monitor not powering up after sitting for a long time (overnight or during the day throughout work). When I would wake the computer up, the backlight would flick on for a second then go out. Sometimes it would take many tries to get it to come on. Once the monitor came on, it worked flawlessly until another long duration of being powered off.

    I thought the problem would be bad caps but I checked both of the caps on the board and they are fine. I also tried powering the monitor from...
    03-07-2023, 12:23 AM
  • triplefour
    TCL 75S421 has sound but no backlight not even a flash
    by triplefour
    TCL 75S421
    PSU BOARD: 40-L402H8-PWD1CG
    it shows not even a flash of backlight when powering up.
    but the tv appeas to turn on and i can hear the sound of the menus moving and clicking. i can power down the tv with the button.
    testing the backlights with my tester all 4 strings lit up and showed similar voltage drops. around 110 or so.
    unplug mb and leave only psu plugged into backlights (PSU + BL SELF TEST MODE?) does not light the backlights.
    i do see 24v but 0v on PSON and BLON (i didnt write this down tho so cant be sure)
    with mb connected, PSON...
    11-17-2023, 09:54 PM
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