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Trying to fix broken backlight on a Soniq E55V13A TV

Discussion in 'Troubleshooting and Repair' started by Chris.Mc, Feb 22, 2015.

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  1. Chris.Mc

    Chris.Mc

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    0
    Feb 22, 2015
    Hi, I just found this site when trying to find how to fix a backlight on a TV. It's a Soniq E55V13A (Australian ID). I've done the "flashlight test" and the LCD is fine.

    The backlight is provided by an array of 78 LEDs (2 arrays of 39). The PSU is supplying 75VDC to each array, but I can't figure out what the LED voltage should be.

    Any ideas/tips on what I should do next ?

    Cheers :)
     
  2. hevans1944

    hevans1944 Hop - AC8NS

    4,470
    2,084
    Jun 21, 2012
    Sounds like there is at least one open LED in each array. Are the LEDs individually accessible for probing? If so, you can try putting a jumper across each one in turn (shorting that particular LED) until that string lights up. Remove the short and replace that LED. Of course this method of troubleshooting will not work if more than one LED in the string is open, but it is "quick and dirty" requiring no "test equipment" other than the jumper wire. Be careful not to short out, or make physical contact with, the 75VDC while doing this.

    If there is more than one open-circuit LED in a string, you will need to test each one individually using an external low-voltage power source (a three volt battery... two dry cells in series is fine) and a current-limiting resistor, say 120Ω, 1/2 watt, to start. If this appears to "light up" the LED too much, increase the resistor value. All you are trying to see is whether or not a particular LED lights up. If none of them light up, increase the supply voltage by adding another dry cell in series.

    Do not power up the TV when doing this test! If possible, disconnect the backlight wiring. IMO, an isolated battery is better than a line-operated low-voltage power supply, even if you have one of those handy on your workbench.

    Please let us know if either of these troubleshooting methods helps you solve your problem.
     
  3. Exogator

    Exogator

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    Dec 7, 2017
    I was just wondering if you managed to fix this I have the same tv, mine works fine, backlight and all for anywhere between 30 mins to about 3 hours then the backlight turns off. I've taken it apart and inspected the psu/ driver, nothing appears to be dead. Any help would be appreciated.
     
  4. Thai Nguyen

    Thai Nguyen

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    Dec 14, 2017
    Same with mine... Need to know where I can buy parts for it...
     
  5. kellys_eye

    kellys_eye

    4,276
    1,146
    Jun 25, 2010
    LED back lighting tends to have very specific and sensitive shut down circuitry attached. Shorted LEDs, open-circuit LEDs, over current etc etc any of which may cause a shut down situation. LEDs are also very thermally sensitive (in terms of failure) therefore can cause problems at unspecified times and intervals.

    The only thing you can do is strip out the LEDs and check them. Spares are readily available but you need the part number off the LED strip as they are also fitted as 'left' and 'right'.

    Some TV sets allow the complete LED back light assembly to be accessed easily but many require the actual LCD panel to be removed - not a job for the faint hearted - so some prior experience is useful.
     
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