LG 32 lcd not always turning ON

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  • nathaniel
    Member
    • Jan 2013
    • 35
    • israel

    #1

    LG 32 lcd not always turning ON

    hello everyone

    my lcd started to make trouble turning ON .
    it goes on once a while mainly when i plug out the ac and let it sit for acouple of hours.

    when it's not turning ON the led acts normally (blinks a few time red then solid blue) just display or sound wont .

    it a 32LG32R

    can you please help me out here

    thank you for your time !
    Attached Files
  • CapLeaker
    Leaking Member
    • Dec 2014
    • 7969
    • Canada

    #2
    Re: LG 32 lcd not always turning ON

    verify PSon voltage in both conditions. If you don't get PSon signal from the mainboard, then there is trouble there.

    Comment

    • nathaniel
      Member
      • Jan 2013
      • 35
      • israel

      #3
      Re: LG 32 lcd not always turning ON

      hi
      thanks for the quick reply
      i just tested what i think is PSON
      i get 1.5v when on 0v when off (while still dont have picture)

      is it ok?
      Attached Files

      Comment

      • victor_cj
        Senior Member
        • May 2015
        • 90
        • Romania

        #4
        Re: LG 32 lcd not always turning ON

        Check 12V, 16,5V, 25,2V when PSon is 1,5V. Check at C609 PFC status.
        The art of fighting without fighting

        Comment

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 7969
          • Canada

          #5
          Re: LG 32 lcd not always turning ON

          Originally posted by nathaniel
          hi
          thanks for the quick reply
          i just tested what i think is PSON
          i get 1.5v when on 0v when off (while still dont have picture)

          is it ok?
          So what is the PSon voltage if there is a picture? To me, the PSon voltage is low. But any how, when the TV is turned on, check all the power rails. See if one or all voltage rails are there or missing.

          Comment

          • newtothis
            Badcaps Legend
            • Mar 2013
            • 1556
            • england

            #6
            Re: LG 32 lcd not always turning ON

            Yes PS_ON should be >2.5v to start the set.

            Can you confirm how you are testing and also your meter battery please

            Comment

            • nathaniel
              Member
              • Jan 2013
              • 35
              • israel

              #7
              Re: LG 32 lcd not always turning ON

              i'm get this resaults:

              1.5v - power_on
              5.2v- to logic board
              no 16.5v to " "
              no 12v " " "
              no 24v " inverter board

              i hope i get lucky tomorrow so i can test and compare
              when it does go on.

              victor sorry i don't know what PFC status mean or how to test it.

              *excuse me for my poor knowlege in electronics , but i'm learning quickly
              thank you all for your patience

              Comment

              • newtothis
                Badcaps Legend
                • Mar 2013
                • 1556
                • england

                #8
                Re: LG 32 lcd not always turning ON

                Voltage at main filter cap (The big cap rated 450v) .. Red to + and Black to - : Meter at 600VDC. Careful as working on HOT side of the board.

                What reading do you get when attempting to power the set on?

                Comment

                • saddle_au
                  Waste Warrior
                  • Jan 2013
                  • 121
                  • Australia

                  #9
                  Re: LG 32 lcd not always turning ON

                  If you have replaced the caps on the secondary side of the P/S, I'd check the values of the capacitors around the regulators on the mainboard. Also the two diodes around the switcher, D1100 and D1102.

                  I've seen the mainboard sit and play dumb when the standby circuits could not startup the main processor because of odd waves coming out of the mainboard switchers. Leaky blocking diodes caused the voltage wave to rise but then fall back again, unsuccessful starting the switch mode off. Cooling the parts with freeze spray identified the faulty circuit area (lowered the threshold to maintain pulsing), but not the exact parts.
                  Attached Files

                  Comment

                  • nathaniel
                    Member
                    • Jan 2013
                    • 35
                    • israel

                    #10
                    Re: LG 32 lcd not always turning ON

                    update:
                    the set turned on today and i get this readings:

                    power_on is 1.5v as when not turning on
                    but then i get all the other 12v , 16.5v and 24v

                    at the big caps i get 329v when on and 310v when off

                    is the problem in the power board ?

                    * i do not have a capacitance test on my multimeter

                    Comment

                    • newtothis
                      Badcaps Legend
                      • Mar 2013
                      • 1556
                      • england

                      #11
                      Re: LG 32 lcd not always turning ON

                      Originally posted by nathaniel
                      update:
                      the set turned on today and i get this readings:

                      power_on is 1.5v as when not turning on
                      but then i get all the other 12v , 16.5v and 24v

                      at the big caps i get 329v when on and 310v when off

                      is the problem in the power board ?

                      * i do not have a capacitance test on my multimeter
                      329v when all other voltages are present?

                      If so please change your meter battery, I think its bad.

                      PS_ON should be higher than 1.5v and the PFC cap should be >360 when 12v etc are present

                      Comment

                      • nathaniel
                        Member
                        • Jan 2013
                        • 35
                        • israel

                        #12
                        Re: LG 32 lcd not always turning ON

                        i believe the battery is fine (i normally get a battery icon when low)

                        i tested with another one i got - the cap read 333v and 1.52v at power_on

                        * this is the equipment i've got:
                        Attached Files

                        Comment

                        • CapLeaker
                          Leaking Member
                          • Dec 2014
                          • 7969
                          • Canada

                          #13
                          Re: LG 32 lcd not always turning ON

                          I am still not convinced that 1.5v on PSon is correct.
                          I'd disconnect the main board from the PSU and "force" the PSU on. Check if all the rails come up on the PSU.
                          Usually it is done by using a 1k ohm resistor from STBY to PSon and another one from STBY to BLon (backlight). As soon as you plug it in, the backlight should be on and all the voltage rails should be on as well.

                          Also the 330V on the filter cap is low. Should be more than 360V. Not sure if you meter is good or not...
                          Last edited by CapLeaker; 05-30-2015, 01:14 PM.

                          Comment

                          • vinceroger69
                            Badcaps Legend
                            • Mar 2012
                            • 6714
                            • uk

                            #14
                            Re: LG 32 lcd not always turning ON

                            whats the power board model number? maybe theres a schematic about

                            Comment

                            • newtothis
                              Badcaps Legend
                              • Mar 2013
                              • 1556
                              • england

                              #15
                              Re: LG 32 lcd not always turning ON

                              Can you take a picture of what setting you are testing on the meter please

                              Comment

                              • victor_cj
                                Senior Member
                                • May 2015
                                • 90
                                • Romania

                                #16
                                Re: LG 32 lcd not always turning ON

                                Originally posted by nathaniel
                                i believe the battery is fine (i normally get a battery icon when low)

                                i tested with another one i got - the cap read 333v and 1.52v at power_on

                                * this is the equipment i've got:
                                You must have 385-400V, PFC working bad in this case.
                                The art of fighting without fighting

                                Comment

                                • victor_cj
                                  Senior Member
                                  • May 2015
                                  • 90
                                  • Romania

                                  #17
                                  Re: LG 32 lcd not always turning ON

                                  Originally posted by nathaniel


                                  victor sorry i don't know what PFC status mean or how to test it.
                                  PFC ON mean 385-400V at C609
                                  PFC OFF mean 290-315V at C609
                                  PFC working bad mean 316-384V at C609
                                  The art of fighting without fighting

                                  Comment

                                  • newtothis
                                    Badcaps Legend
                                    • Mar 2013
                                    • 1556
                                    • england

                                    #18
                                    Re: LG 32 lcd not always turning ON

                                    Originally posted by victor_cj
                                    You must have 385-400V, PFC working bad in this case.
                                    The set wouldn't start at 1.5v though and I would be surprised if he had 12v and 24v if the PFC cap did indeed only have 330v

                                    Comment

                                    • newtothis
                                      Badcaps Legend
                                      • Mar 2013
                                      • 1556
                                      • england

                                      #19
                                      Re: LG 32 lcd not always turning ON

                                      Originally posted by victor_cj
                                      PFC ON mean 385-400V at C609
                                      PFC OFF mean 290-315V at C609
                                      PFC working bad mean 316-384V at C609
                                      PFC will work at >360v

                                      Comment

                                      • victor_cj
                                        Senior Member
                                        • May 2015
                                        • 90
                                        • Romania

                                        #20
                                        Re: LG 32 lcd not always turning ON

                                        Originally posted by newtothis
                                        The set wouldn't start at 1.5v though and I would be surprised if he had 12v and 24v if the PFC cap did indeed only have 330v
                                        This model have 1,2-2,7V PSon.
                                        The art of fighting without fighting

                                        Comment

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