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    #1

    LG 22LH20D TV wont power up

    Hi Guys

    I have a LG 22LH20D LCD TV that wont power up.
    I have disassembled and checked the power coming in. I get 230VAC at the power socket right through to the bridge rectifier. I have also checked the small connector that goes to the main board and have 16v at pin 1 and 2, 0v at 3 and 4, 5.2v at 5 and 6, 0v at 7 and 8, 0v at 9 and 10, 3.3v at 11.

    I have also checked the power switch on top and get 3.3 v to the switch, 3.3v back untill the button is pressed the drops to 0v, so i am taking that i am getting a signal to the main board to turn on the power, but get no signal from the main board to the power board.

    The blue power LED is on.

    The symptoms coming up to the final fault were the TV would intermitently switch on and off, and then it switched of one last time and has never been able to switch back on since.

    Please see photos for board layout.

    Any help would be greatly appreciated as i have three of these TVs, 2 are starting to do the turn off intermitently. So would like to fix these before they all go. They are all out of warranty.
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    #2
    Re: LG 22LH20D TV wont power up

    Pretty good pictures, but they have common flaws which drives me to frustration.

    Proper orientation of a board in a picture can help us help you. You list the voltages you found at the connector, but neither picture of the power supply board shows the legend for that connector clearly. With some difficulty, I can determine this is a single power supply, all voltages are present, but the inverter is not switched on. The main power supply is always on.

    The main board presents more challenges. I note two LDO regulators on the front IC403 and IC405, plus one on the back, IC??? (the number is hidden). There appear to be three more power supply areas on the front (2 o'clock), 5 o'clock, 7 o'clock).

    I would suggest checking these for reasonable output voltages.

    The service manual can be found here.


    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment

      #3
      Re: LG 22LH20D TV wont power up

      Just from my experience with Sam Young capacitors, I'd replace all of those 1000 uF's and lower (electrolytics). This problem seems like a capacitor failure - slow intermittent death vs catastrophic.
      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

      Comment

        #4
        Re: LG 22LH20D TV wont power up

        Hi there PlainBill
        Sorry about the picture orientation, an over sight on my behalf.

        I have checked the 3 LDO regs and have all the correct voltages coming out of them IC403 3.3v, IC405 1.8v, IC901 3.3v (on rear).

        The legend for the connector is on the rear of the board. It reads
        1. Small/15v
        2. Small/15v
        3. GND
        4. GND
        5. +5v-ST
        6. +5v-ST
        7. GND
        8. GND
        9. INV-CTL
        10. PWR-DIM-Large
        11. A-DIM-Small

        If i bridge pin 9 with pin 5/6 i can get the CCFL's to come on, so i will assume that all is well with the Power Board.
        I have a problem where all the IC numbers in the manual are nowhere near the ones i have on the main board, So i have become stumped with where to check for the power on button control circuit. Approx 4 o'clock is where it all starts (on front of main board where 3 pin plug is) what would you suggest i should do next. or is it just a case of replace the main board?

        Cheers

        Comment

          #5
          Re: LG 22LH20D TV wont power up

          Originally posted by racing00 View Post
          Hi there PlainBill
          Sorry about the picture orientation, an over sight on my behalf.

          I have checked the 3 LDO regs and have all the correct voltages coming out of them IC403 3.3v, IC405 1.8v, IC901 3.3v (on rear).

          The legend for the connector is on the rear of the board. It reads
          1. Small/15v
          2. Small/15v
          3. GND
          4. GND
          5. +5v-ST
          6. +5v-ST
          7. GND
          8. GND
          9. INV-CTL
          10. PWR-DIM-Large
          11. A-DIM-Small

          If i bridge pin 9 with pin 5/6 i can get the CCFL's to come on, so i will assume that all is well with the Power Board.
          I have a problem where all the IC numbers in the manual are nowhere near the ones i have on the main board, So i have become stumped with where to check for the power on button control circuit. Approx 4 o'clock is where it all starts (on front of main board where 3 pin plug is) what would you suggest i should do next. or is it just a case of replace the main board?

          Cheers
          Since you have one dead and several showing signs of failure it is worth pursuing this a little further. One thing strikes me - by your description, this appears to be a progressive deterioration. That screams 'Capacitor failing!!!' to me.

          I've been working on a couple of outdoor projects (mainly painting) and the current forecast indicates a good chance of rain for the next four days. That puts the projects on hold. I'll download the service manual and see if I can identify any further areas to check.

          PlainBill
          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

          Comment

            #6
            Re: LG 22LH20D TV wont power up

            After examining a service manual, I've identified a couple more voltage regulators. What are the part numbers of IC902 (bottom center) and IC906 (lower left corner)?

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment

              #7
              Re: LG 22LH20D TV wont power up

              Hi PlainBill

              I have examined the IC's and numbers are as follows

              IC902

              MP2212DN
              91962508
              MPS910

              IC906

              MP2305DS
              91846368
              MPS908

              Comment

                #8
                Re: LG 22LH20D TV wont power up

                What type of caps did you replace the Sam Young caps with? Were they low ESR caps?
                The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                Comment

                  #9
                  Re: LG 22LH20D TV wont power up

                  Originally posted by racing00 View Post
                  Hi PlainBill

                  I have examined the IC's and numbers are as follows

                  IC902

                  MP2212DN
                  91962508
                  MPS910

                  IC906

                  MP2305DS
                  91846368
                  MPS908
                  The MP2212DN is a step down converter. Pin 3 is the input; pins 6 & 7 are the output, but they will have a lot of hash on them; trace the output to an inductor and measure the output voltage at the far side (left side in the picture) of the inductor directly above it. Report that voltage.

                  The MP2305DS is a similar part; pin 2 is the input, pin 3 is the output, but again measure the output voltage at the far side (left side in the picture) of the inductor L917 and report it.

                  PlainBill
                  Last edited by PlainBill; 04-16-2011, 07:28 AM.
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment

                    #10
                    Re: LG 22LH20D TV wont power up

                    Hi everybody

                    Nice to have someone to have same problem as I have. But in your case power led on . Mine has no light but power is coming from psi.btw I have lg LCD tv m2362d-pt model. Can I have a service manual for this.

                    Comment

                      #11
                      Re: LG 22LH20D TV wont power up

                      Originally posted by Rev11 View Post
                      Hi everybody

                      Nice to have someone to have same problem as I have. But in your case power led on . Mine has no light but power is coming from psi.btw I have lg LCD tv m2362d-pt model. Can I have a service manual for this.
                      Please don't hijack threads!!! If you have the same model, or the same problem on a slightly different model it might be acceptable. But jumping in with a different model with different symptoms is going to cause problems.

                      No luck on finding schematics. Now go ask the moderators to move these posts to a new thread.

                      PlainBill
                      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                      Comment

                        #12
                        Re: LG 22LH20D TV wont power up

                        Hi I have changed my problem same as that of racing" guy by tweaking a ic in main board. Hope so we are on at same longitude and latitude now

                        Comment

                          #13
                          Re: LG 22LH20D TV wont power up

                          Originally posted by Dgtech View Post
                          What type of caps did you replace the Sam Young caps with? Were they low ESR caps?
                          Hi DGtech The caps are Jamicon that i have recapped with and yes low esr.

                          Comment

                            #14
                            Re: LG 22LH20D TV wont power up

                            i have solved my problem by resetting microcontroller.

                            Comment

                              #15
                              Re: LG 22LH20D TV wont power up

                              Originally posted by PlainBill View Post
                              The MP2212DN is a step down converter. Pin 3 is the input; pins 6 & 7 are the output, but they will have a lot of hash on them; trace the output to an inductor and measure the output voltage at the far side (left side in the picture) of the inductor directly above it. Report that voltage.

                              The MP2305DS is a similar part; pin 2 is the input, pin 3 is the output, but again measure the output voltage at the far side (left side in the picture) of the inductor L917 and report it.

                              PlainBill
                              MP2212DN

                              Pin 3 is 5.22v
                              Pin 6,7 on inductor is 1.262v and very stable

                              MP2305DS

                              Pin 2 is 16.67v
                              Pin 3 is 5.114v

                              Comment

                                #16
                                Re: LG 22LH20D TV wont power up

                                .
                                The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                                Comment

                                  #17
                                  Re: LG 22LH20D TV wont power up

                                  Originally posted by racing00 View Post
                                  MP2212DN

                                  Pin 3 is 5.22v
                                  Pin 6,7 on inductor is 1.262v and very stable

                                  MP2305DS

                                  Pin 2 is 16.67v
                                  Pin 3 is 5.114v
                                  It looks like the MP2305DS is dropping the main supply to 5 volts. The voltage out of the MP2212DN is within spec for a 1.25 volt supply. At this point I'm out of ideas.

                                  PlainBill
                                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                  Comment

                                    #18
                                    Re: LG 22LH20D TV wont power up

                                    Hi All

                                    Just to let you all know that i have now fixed this TV.
                                    It looks like the main CPU has either lost its program or had a spike.
                                    I replaced the main board which is very cheap (i was pleasantly suprised)

                                    Hey presto all fixed.

                                    Not sure what had caused the failure but will dig further to find out exactly what caused it and will post further downnn the track.

                                    Thanks to all for all their time and help.

                                    Comment

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