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Vestel 17ips11

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    #1

    Vestel 17ips11

    So as the title says... I have got the most F-ed up power supply that I need to somehow repair since it is either impossible to get it in Croatia or too expensive.

    First things first, it is a 32" Quadro LED LCD TV which all of a sudden did not wont to turn on, no backlight but there was some picture that could be seen in a dark room and the sound was OK.

    Opened it up, tested the LED strips and there were 6 dead LEDs, replaced them put everything back up, nothing changed. Measured the output on the power supply and it gives 42 V on DC range and 96,4 V on AC that goes straight to zero after a few seconds.

    I replaced the caps but that didn't fix the problem, and I dont know where to look since this the first LED that I am trying to repair.

    Any suggestions?

    The pics are here.
    Attached Files
    Last edited by CroTech; 01-05-2017, 12:38 PM.
    Tags: None
    #2
    Re: Vestel 17ips11

    I recall there is a trick to bypassing LED strings with a zener diode of same voltage, to test if it's LEDs or PSU. Maybe some LEDs are still bad?
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment

      #3
      Re: Vestel 17ips11

      With the leds disconnected what DC voltage do you have at the led output before it falls.
      How many leds were in series?
      Willing to help but I'm no expert.

      Comment

        #4
        Re: Vestel 17ips11

        Looking at the capacitor close to connector CN101 rated at 100V I would expect the Led voltage to be somewhere near that voltage 70 - 80 V but this is just guess work.
        Willing to help but I'm no expert.

        Comment

          #5
          Re: Vestel 17ips11

          The stripes are fine. I replaced the bad LEDs with new ones and tested it with 9v battery and 2 needles and every one of those shines bright light... The voltage without LEDs connected are the same and drop to zero. So it seems that fail protection turns on even though LEDs are not connected.

          Comment

            #6
            Re: Vestel 17ips11

            Have you checked the Backlight On signal remains high at CN100 Pin 5
            Last edited by dick_barton; 01-06-2017, 02:37 PM.
            Willing to help but I'm no expert.

            Comment

              #7
              Re: Vestel 17ips11

              Originally posted by lule.nikolic View Post
              The stripes are fine. I replaced the bad LEDs with new ones and tested it with 9v battery and 2 needles and every one of those shines bright light... The voltage without LEDs connected are the same and drop to zero. So it seems that fail protection turns on even though LEDs are not connected.
              i dont know from where you got this way to test TV LED strips. this 2 needles you used reverse them with yours DMM and test the LED as diode way.. the one beep are bad. then one had Vf less than as usual are bad too. check and you will find you have one had diode shorted

              Comment

                #8
                Re: Vestel 17ips11

                Originally posted by Diah View Post
                i dont know from where you got this way to test TV LED strips. this 2 needles you used reverse them with yours DMM and test the LED as diode way.. the one beep are bad. then one had Vf less than as usual are bad too. check and you will find you have one had diode shorted
                That's a good idea.
                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                -David VanHorn

                Comment

                  #9
                  Re: Vestel 17ips11

                  Originally posted by dick_barton View Post
                  Have you checked the Backlight On signal remains high at CN100 Pin 5
                  Sorry I did not check but I will as soon as I get some free time...

                  Let me explain my "checking LED method" since it is simple, fast and bulletproof.

                  I take a 9V battery and solder a wire to a + and a wire to -
                  Now I solder + wire to a sewing needle, and - wire to a another sewing needle. Why sewing needle? Cause they are conductors and they can easily punctre the LED strip isolator. Now when the "TESTING DEVICE" is ready I take one end and try to pin the LED, once I see bright light from it I know that LED is good and if it is not shining any light I try to switch polarity and if that does not work, I take my hot air gun and solder a new one and then test it again, I can also test up to 3 LEDs in series but then they shine a little dimmer.

                  Comment

                    #10
                    Re: Vestel 17ips11

                    But if you put 9V across a 3V led you have a very high chance of burning it out almost immediately, or if not you put the led under stress so that it fails sooner rather than later. Even if you do the same across a single 6V led.

                    Testing across 3 leds in series (3 x 3V = 9V) is the safer method.
                    Willing to help but I'm no expert.

                    Comment

                      #11
                      Re: Vestel 17ips11

                      I know, but having it stressed for half a second I dont think it damages it cause I have seen them shine even brighter through original power supply, that is actually how TV manufacturers make sure it fails after the warranty is out plus it is a old battery that is half way drained, that is why when you connect it to 3 LEDs in series they shine poorly.

                      As soon as I get my hands on TV again I will measure CN100 pin5

                      Comment

                        #12
                        Re: Vestel 17ips11

                        It's still bad practice. It's not terribly difficult to add even just one resistor.
                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                        -David VanHorn

                        Comment

                          #13
                          Re: Vestel 17ips11

                          Got the PCB to a frend of mine who repairs TVs and he told me that both of the SMD ICs on the back of the PCB (green side) seem to have wrong readings and that they should be replaced, so I am gone order new ones and ones I replace them I am going to make a new post.

                          Thanks guys

                          Comment

                            #14
                            Re: Vestel 17ips11

                            Led driver Ic.
                            Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                            https://www.facebook.com/Telford-Tel...7894576335359/

                            Comment

                              #15
                              Re: Vestel 17ips11

                              Originally posted by ReeceyBurger123 View Post
                              Led driver Ic.
                              ReeceyBurger, I presume you had the same problem? Cause I was reading about how dead LEDs and blinking LEDs can kill the power supply board.

                              Comment

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