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Philips 65PUT6121 - no backlight

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    #1

    Philips 65PUT6121 - no backlight

    Hey guys,

    I have picture with flashlight but no backlight. Logo comes on quickly with low light before disappearing. When checking behind the tv I see backlight turning on in some holes before turning off and that's when the room is pitch black. Impossible to see otherwise. That explains the logo barely visible before disappearing. Don't know about sound but it should be fine. TV stays on.

    Here are some pictures and numbers taken with TV on.

    PIN1,2,3=VIN 33V
    PIN4,5,6 =GND 0V
    PIN7 =+18V 12V ???
    PIN8=BL-ON 3.2V
    PIN9=DIM 2.8V
    PIN10=ADIM basically 0


    PIN1=+VLED1 33V
    PIN12=+VLED2 33V
    PIN2,6,7,11=NC 2 and 11 = 33V, 6 and 7 = 3.8V
    PIN3,4,5=-VLED1 3.8V
    PIN8,9,10=-VLED2 3.8V


    So PIN7 shows 12V instead of 18V.


    Should I open up completely and check the strips? I don't have a LED tester and if some LEDs are broken or burnt it should show right?

    Please help me
    Tags: None
    #2
    Re: Philips 65PUT6121 - no backlight









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      #3
      Re: Philips 65PUT6121 - no backlight

      how old is the tv, probably at least 2 yrs old, so at a guess the leds will need replacing soon anyway and for around £25 you can get a full complete brand new set. But highly suspect leds are the cause.
      Connect an external source with sound playing so you can confirm the tv is on and working but the fact you can see a faint image already proves this really!

      How did you measure the led voltages? black probe to gnd, chassis?

      What voltages do you get on pins 1, 2, 11 and 12 with led connector removed?

      I think you will find 8 strips with 14 leds per strip, see photo. And a pair of led wires will drive 2 strips, guessing each pair of strips will be connected in parallel.
      Attached Files
      Last edited by notallbad; 09-03-2023, 02:09 PM.

      Comment

        #4
        Re: Philips 65PUT6121 - no backlight

        +32 volts is the raw supply for the led circuit, If the led's are working, this voltage will be boosted to a higher voltage, but when there is even one bad led, the circuit will go into protection and shut down. So you likely have one or more bad led's in the panel.

        If you check that +VLED voltage as you turn on the tv, you might see that voltage come up for a second.

        Comment

          #5
          Re: Philips 65PUT6121 - no backlight

          Originally posted by notallbad View Post
          how old is the tv, probably at least 2 yrs old, so at a guess the leds will need replacing soon anyway and for around £25 you can get a full complete brand new set. But highly suspect leds are the cause.
          Connect an external source with sound playing so you can confirm the tv is on and working but the fact you can see a faint image already proves this really!

          How did you measure the led voltages? black probe to gnd, chassis?

          What voltages do you get on pins 1, 2, 11 and 12 with led connector removed?

          I think you will find 8 strips with 14 leds per strip, see photo. And a pair of led wires will drive 2 strips, guessing each pair of strips will be connected in parallel.
          It's from 2016. I tried playing from my laptop some music but since I couldn't see shit when trying to navigate on source I gave up on playing sound. I might just connect it to the tv outlet and see if I get some sound from there.

          Black probe to chassis.

          I didn't try voltages with panel disconnected. Will it make a difference? Since I suspected it was the strips I packed up the TV with all screws and everything.

          Also I think some voltages should be 0 and not 3.8. I probably didn't notice my multimeter jumping to mV when checking some pins...
          Last edited by Rubenlily; 09-03-2023, 04:47 PM.

          Comment

            #6
            Re: Philips 65PUT6121 - no backlight

            Originally posted by R_J View Post
            +32 volts is the raw supply for the led circuit, If the led's are working, this voltage will be boosted to a higher voltage, but when there is even one bad led, the circuit will go into protection and shut down. So you likely have one or more bad led's in the panel.

            If you check that +VLED voltage as you turn on the tv, you might see that voltage come up for a second.
            Thanks for the reply. Makes me more confident to order strips.

            Comment

              #7
              Re: Philips 65PUT6121 - no backlight

              Ideally you need to strip the tv down to access the led strips to confirm you are ordering the correct ones though I havent really had any issues ordering according to the panel i.d.

              Same tv model can have different panels and hence different led strips.

              Remove the rear panel to confirm the panel, will be a label attached to the metal chassis with the panel number and use to cross reference to the led strips compatibility.
              Last edited by notallbad; 09-04-2023, 03:31 PM.

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                #8
                Re: Philips 65PUT6121 - no backlight

                Also, you can download the service manual from this page:
                https://www.electronica-pt.com/esque...ileinfo/69941/

                Comment

                  #9
                  Re: Philips 65PUT6121 - no backlight

                  I just repaired a Phillips with this exact symptom. It was one LED. And no I couldn't identify which light was out after opening it. It didn't look burnt. I had to LED test every individual one. LED tester is best way imo to confirm without having to open it up. Some people here say it's unreliable because of not enough mamps to "confirm" but it's never failed me yet.

                  Comment

                    #10
                    Re: Philips 65PUT6121 - no backlight

                    Originally posted by notallbad View Post
                    Ideally you need to strip the tv down to access the led strips to confirm you are ordering the correct ones though I havent really had any issues ordering according to the panel i.d.

                    Same tv model can have different panels and hence different led strips.

                    Remove the rear panel to confirm the panel, will be a label attached to the metal chassis with the panel number and use to cross reference to the led strips compatibility.
                    I have a new problem. I'm just replacing the strips when I see the panel cabel is burned. Should it be fine or should I get a new cable?



                    Attached Files

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                      #11
                      Re: Philips 65PUT6121 - no backlight

                      Originally posted by notallbad View Post
                      how old is the tv, probably at least 2 yrs old, so at a guess the leds will need replacing soon anyway and for around £25 you can get a full complete brand new set. But highly suspect leds are the cause.
                      Connect an external source with sound playing so you can confirm the tv is on and working but the fact you can see a faint image already proves this really!

                      How did you measure the led voltages? black probe to gnd, chassis?

                      What voltages do you get on pins 1, 2, 11 and 12 with led connector removed?

                      I think you will find 8 strips with 14 leds per strip, see photo. And a pair of led wires will drive 2 strips, guessing each pair of strips will be connected in parallel.

                      Please check my latest post. I'm soon done with replacing the LEDs and don't wanna have done it for nothing lol

                      Comment

                        #12
                        Re: Philips 65PUT6121 - no backlight

                        Originally posted by EazyBone View Post
                        I just repaired a Phillips with this exact symptom. It was one LED. And no I couldn't identify which light was out after opening it. It didn't look burnt. I had to LED test every individual one. LED tester is best way imo to confirm without having to open it up. Some people here say it's unreliable because of not enough mamps to "confirm" but it's never failed me yet.
                        I don't have led tester. Just replacing all strips

                        Comment

                          #13
                          Re: Philips 65PUT6121 - no backlight

                          Fuck me the cable is total burned. Have to get a new one... hope I don't have to replace the contact too................

                          Comment

                            #14
                            Re: Philips 65PUT6121 - no backlight

                            Damn that's fried, I wonder what caused it.

                            Comment

                              #15
                              Re: Philips 65PUT6121 - no backlight

                              Originally posted by nomoresonys View Post
                              Damn that's fried, I wonder what caused it.
                              I'm gonna go with electricity. That'd be my guess

                              But yea that's pretty nuts. Haven't seen that yet

                              Comment

                                #16
                                Re: Philips 65PUT6121 - no backlight

                                Originally posted by Rubenlily View Post
                                Fuck me the cable is total burned. Have to get a new one... hope I don't have to replace the contact too................
                                Solder the cable on the pcb, cables are not sold by Philips.

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