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when i turn on, Philliips TV is not on

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    when i turn on, Philliips TV is not on

    Hi all, my TV is Phillips 55PFL5505D/F7. when i powered up nothing happened. standby light not on. I opened the cover and try to measure voltage. I do not have 5Vdc, 3.3v at the connector 2.

    IC902 (I replaced new one still same voltage)
    pin1 --> 0.025v
    pin2 --> 0.485v
    pin3 --> 0v
    pin4 --> 0v
    pin5 --> 0v

    IC901 (I replaced new one still same voltage)
    pin1 --> 0v to 1.2v (changing, not stable)
    pin2 --> 4.96v
    pin3 --> 0v
    pin4 --> 169.7v
    pin5 -->169.7v
    pin6 -->0v
    pin7 -->10v to 16v (changing, not stable,) {when i remove the C912, it become stable 13V, i replace new cap and still changing)
    pin8 -->0v

    T901
    pin1 --> 0.009v
    pin2 --> 0.010v
    pin3 --> 0.015v
    pin4 --> 0.006v
    pin5 --> 0v
    pin6 --> 0v
    pin7 --> 0v
    pin9 --> 169.4v
    pin10 --> 169.7v


    Can anyone help me please?
    Attached Files
    Last edited by Nish; 12-25-2019, 11:12 AM. Reason: forget to add details

    #2
    Re: when i turn on, Philliips TV is not on

    I would check for shorted diodes and transistors on the power supply. Need the pin labels and voltages on the power supply connector. There should be troubleshooting flowchart in service manual.
    Last edited by neilc6; 12-25-2019, 01:37 PM.

    Comment


      #3
      Re: when i turn on, Philliips TV is not on

      CN5
      pin1 --> 0V pin6 --> 0V
      pin2 --> 0V pin7 --> 0V
      pin3 --> 0V pin8 --> 0V
      pin4 --> 0V pin9 --> 0V
      pin5 --> 0V pin10 --> 0V

      CN5
      pin1 --> 0V pin8 --> 0V
      pin2 --> 0V pin9 --> 0V
      pin3 --> 0V pin10 --> 0V
      pin4 --> 0V pin11 --> 0V
      pin5 --> 0V pin12 --> 0V
      pin6 --> 0V pin13 --> 0V
      pin7 --> 0V pin14 --> 0V


      CN2
      pin1 --> 0V pin8 --> 0V
      pin2 --> 0V pin9 --> 0V
      pin3 --> 0V pin10 --> 0V
      pin4 --> 0V pin11 --> -0.139V
      pin5 --> 0V pin12 --> 0V
      pin6 --> 0V pin13 --> 0V
      pin7 --> 0V pin14 --> 0V

      Comment


        #4
        Re: when i turn on, Philliips TV is not on

        On ic901, pin 7 (vcc) is changing because the ic is trying to start but is being shut down. It will only rise to 17 volts due to the zener diode ZD904.
        Do you get any voltage at all on C951a ? If it is 0 volts, check the diodes D950~952 and also ZD951, it could be shorted killing the 5 volts.
        I see there is also 3.1 volts on D903/C906, this also indicates the secondary's are trying to produce some voltage.
        so you should see some voltage on C951a
        If the original ic was bad, check the two resistors R909,R910 off pin3,
        Last edited by R_J; 12-25-2019, 03:06 PM.

        Comment


          #5
          Re: when i turn on, Philliips TV is not on

          do u check optocoupler?

          in some motherboard i use dc power supply 30v 5amp in big caps and see if is taking any power(something getting hot) or not

          Comment


            #6
            Re: when i turn on, Philliips TV is not on

            C951a = 0.170v ( negative probe in negative of cap)
            Those diode looks Ok, I will remove those diode.

            Comment


              #7
              Re: when i turn on, Philliips TV is not on

              I removed those 3 diode, measured in diode mode it reads 0.239v.

              Comment


                #8
                Re: when i turn on, Philliips TV is not on

                Opps I blow out the chip IC901. I need to order parts to replace. I think I short.
                Attached Files
                Last edited by Nish; 12-25-2019, 04:03 PM.

                Comment


                  #9
                  Re: when i turn on, Philliips TV is not on

                  C951a = 0.170v ( negative probe in negative of cap)
                  Those diode looks Ok, I will remove those diode.

                  Comment


                    #10
                    Re: when i turn on, Philliips TV is not on

                    Thank you neilc6, R_J and digitalpc for helping me to solve my problem.

                    I have replaced D951, D950, ZD951 and the the IC901 since I blown up.

                    As per digitalpc I applied and I found C952 gets hot. I have replaced it.

                    Now the voltage at the IC901

                    Before solder all pin
                    Pin1--》0v
                    Pin2--》3.969
                    Pin3--》0.741
                    Pin4--》168.5
                    Pin5--》168 (soldered)
                    Pin6--》0
                    Pin7--》8.75
                    Pin8--》0 (soldered)

                    After soldered all pin
                    Pin1--》0v
                    Pin2--》2.86
                    Pin3--》0.741
                    Pin4--》166.5
                    Pin5--》166
                    Pin6--》0
                    Pin7--》14.94 (now stable)
                    Pin8--》0

                    C951a = 0.120v

                    I don't have 3.1v now

                    Comment


                      #11
                      Re: when i turn on, Philliips TV is not on

                      I don't have 3.1v now
                      Then the ic is not operating, When you blew up the ic you must have damaged more components.
                      Check R909/R910, D906, R916, ZD904 Check the transformer winding between pins 5,6 & 7, (should not be open)

                      Did you replace ic901 with a DNP005? where did you get it?
                      Last edited by R_J; 01-08-2020, 01:44 PM.

                      Comment


                        #12
                        Re: when i turn on, Philliips TV is not on

                        Do you think transformer could damaged?
                        Attached Files

                        Comment


                          #13
                          Re: when i turn on, Philliips TV is not on

                          R906 and R910 is OL, when I read with multimeter.
                          Transformer winding pin5,6,7 are connected

                          Comment


                            #14
                            Re: when i turn on, Philliips TV is not on

                            D906=0.4, r916 =5.1, zd904=0.4

                            Comment


                              #15
                              Re: when i turn on, Philliips TV is not on

                              Well if R909 and R910 are open, the ic will not function. (did you mean R909 instead of R906?)
                              The transformer is likely ok. If R916 is ok, its liely D906 is ok, zd904 is likely ok also.

                              Comment


                                #16
                                Re: when i turn on, Philliips TV is not on

                                Yes it's R909, I will replace and update the status.

                                Comment


                                  #17
                                  Re: when i turn on, Philliips TV is not on

                                  I replace with new resistor R909 and R910 and still no 3v. Do you think it could be the caps c908 and C906. How can I test? If i remove, do you think the IC give the output?

                                  Comment


                                    #18
                                    Re: when i turn on, Philliips TV is not on

                                    R909 and R910 = 2ohm
                                    I soldered R909 =5.11 , R910=3.1

                                    Comment


                                      #19
                                      Re: when i turn on, Philliips TV is not on

                                      I have 0.025 on D604 and D603. I measure both way ( red and black probes switched).I removed those diode and on the pad it shows that value. How come?

                                      Comment


                                        #20
                                        Re: when i turn on, Philliips TV is not on

                                        Why are you looking at that circuit? you need to fix the standby circuit first. Look at the schematic...there are two resistors across D604 and D603... R617 (51Ω) and R620 (51Ω)

                                        Comment

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