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    Dell U2312H Repair

    I have a Dell U2312H that suddenly won't turn on anymore. The display and
    backlight won't turn on; the blue power LED stays off even when I press the
    power button. These have the L0281-1N power boards which are the same ones used
    for the Dell P2312H and P2012H, among others (according to Google).
    Unfortunately I can't find any schematics for this particular board.

    I have made some measurements to some of the components from the power board
    and main board. These were all tested in circuit (i.e. I didn't solder them
    out). Readings are ordered by pins (e.g. 1, 2, 3, etc.). Diodes were tested
    using the continuity tester of my multimeter; however, I don't know what the
    units for these are. I have upload the images of the boards to imgur. If you
    need a close up picture of some parts of the board, please don't hesitate to
    notify me. Thank you!


    Power Board

    I805

    AUK
    81826
    A78R12PI

    12v, 0.8mv, 0v, 0.263v

    I802 (Optocoupler)

    L1125
    817D
    Y

    Red to Pin 1 + Black to Pin 2: 567
    Black to Pin 1 + Red to Pin 2: 567

    I801 (PWM Controller)

    LD7575BGS
    112731

    Pins 1 - 4: -0.48v - -0.58v
    Pins 6 - 8: -0.35, -0.02, 0.66

    Q121

    D482
    BA1U15

    Black to S + Red to G: 16.31MΩ
    Black to S + Red to D: 0.82MΩ (and increasing)
    Black to G + Red to D: 1.11MΩ

    D805

    pec 1329
    ER1002FCT

    Black to Pin 1 + Red to Pin 2: 581 and increasing
    Black to Pin 1 + Red to Pin 3: 001
    Black to Pin 2 + Red to Pin 3: 395
    Black to Pin 2 + Red to Pin 1: 395

    D812

    pec 1349
    ER1002FCT

    Black to Pin 1 + Red to Pin 2: 892
    Black to Pin 1 + Red to Pin 3: 002
    Black to Pin 2 + Red to Pin 3: 399
    Black to Pin 2 + Red to Pin 1: 399

    D810

    N 1G
    FCQS20A065

    Black to Pin 1 + Red to Pin 2: 481 and increasing
    Black to Pin 1 + Red to Pin 3: 002
    Black to Pin 2 + Red to Pin 3: 135
    Black to Pin 2 + Red to Pin 1: 135

    Q803

    A
    2761I
    124 125

    Black to S + Red to G: 0.148MΩ
    Black to S + Red to D: 1.2MΩ
    Black to G + Red to D: 1.4MΩ

    R811

    1.1Ω (should be 0.36Ω 2WJ)

    Main Board

    I301

    N252
    G1084-33

    0v, 0.18v, 5.0v

    I302

    UTC
    LD1117AG
    12A010GTG

    0v, 0v, 0.18v

    I308

    D|| 1fB
    17-33

    0v, 0v, 0v

    #2
    Re: Dell U2312H Repair

    I am also attaching the images in this post. So sorry for using another image hosting site.
    Attached Files

    Comment


      #3
      Re: Dell U2312H Repair

      "I301

      N252
      G1084-33

      0v, 0.18v, 5.0v"

      So you are getting 5V feeding this 3.3V Regulator but the out put is only 0.18V, it can be bad regulator or the output pin is over loaded.
      You should check the resistance between GND and the output pin to see if it shows very low resistance (<50 Ohms).
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
      http://www.badcaps.net/forum/showthr...956#post305956

      Voltage Regulator (LDO) testing:
      http://www.badcaps.net/forum/showthr...999#post300999

      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
      http://s807.photobucket.com/user/budm/library/

      TV Factory reset codes listing:
      http://www.badcaps.net/forum/showthread.php?t=24809

      Comment


        #4
        Re: Dell U2312H Repair

        budm, I have different readings based on the polarity of my probes:

        Black on GND + Red on Vout: 1.336KΩ
        Black on Vout + Red on GND: 0.353KΩ

        Comment


          #5
          Re: Dell U2312H Repair

          Those are OK, nothing <50 Ohms.
          So at this point that 3.3V regulator is probably bad.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment


            #6
            Re: Dell U2312H Repair

            Do you have any idea why it went bad? I'm wondering if and what components up the chain that might have caused I301 to go bad.

            How about I802? I read that I should only have one reading for the LED pins; but I was able to get a second reading, with the polarity reversed.

            Comment


              #7
              Re: Dell U2312H Repair

              Originally posted by doomsweek View Post
              Do you have any idea why it went bad? I'm wondering if and what components up the chain that might have caused I301 to go bad.
              Not really. Sometimes they just die. Old age perhaps.
              Replace it and see what happens.

              Originally posted by doomsweek View Post
              How about I802? I read that I should only have one reading for the LED pins; but I was able to get a second reading, with the polarity reversed.
              Yes the LED inside the optocoupler should only test OK one way, but you are testing it in-circuit. Another part in parallel with it may well be causing a spurious reading. You would have to remove it and test it out-of-circuit to be sure.
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment


                #8
                Re: Dell U2312H Repair

                I302 get the 3.3V INPUT from the output of I301, so you need to replace the I301 first.
                These regulators do fail, lot of them in VIZIO TVs, monitors..
                You should also check the capacitance/ESR or replace those filter caps on the input and out side of those regulators.
                Attached Files
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Dell U2312H Repair

                  Hello everyone. The parts I ordered finally arrived yesterday. @budm was right, I only needed to replace the 1084-33 chip to make my monitor work again.

                  Although the monitor already worked without replacing the capacitors, I changed all of the electrolytic capacitors anyway since they were from a known bad manufacturer (Su'scon).

                  Thank you everyone for the help.

                  Comment


                    #10
                    Re: Dell U2312H Repair

                    Thanks for the follow-up.
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment


                      #11
                      Re: Dell U2312H Repair

                      You forgot to check el.cap. ...

                      Comment


                        #12
                        Re: Dell U2312H Repair

                        Just a shout out to doomsweek, I have the same monitor that was occasionally not powering up, initially I was looking to replace all the caps and then when googling the power board I found this post. My 3v regulator seems to be intermittent, currently I have hard wired a small ebay sourced switch mode regulator module set to 3.3v and it is currently working perfectly - just awaiting a new G1084-33 that is on order (stupid shop in my country says I need to order minimum 20 units though)

                        Comment


                          #13
                          Re: Dell U2312H Repair

                          Pardon the newbie question.
                          Where is this G1084-33 located, is it the ic on the top right corner, when looking on the power supply board from the bottom?

                          If so why does mine say D482 GA2428 on it?

                          Got same screen\power supply issue, figured I'd try this cheap fix before I spend on a whole new power supply board.

                          Thanks
                          Attached Files

                          Comment


                            #14
                            Re: Dell U2312H Repair

                            post #1
                            Main Board

                            I301

                            N252
                            G1084-33

                            It is on the main logic board.
                            Never stop learning
                            Basic LCD TV and Monitor troubleshooting guides.
                            http://www.badcaps.net/forum/showthr...956#post305956

                            Voltage Regulator (LDO) testing:
                            http://www.badcaps.net/forum/showthr...999#post300999

                            Inverter testing using old CFL:
                            http://www.badcaps.net/forum/showthr...er+testing+cfl

                            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                            http://s807.photobucket.com/user/budm/library/

                            TV Factory reset codes listing:
                            http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment


                              #15
                              Re: Dell U2312H Repair

                              Duh moment, sorry.
                              Thanks

                              Comment


                                #16
                                Re: Dell U2312H Repair

                                CHeck the voltage output of the regulator first, if it is giving 3.3v then this is not your issue. I actually replaced mine by wiring in one of these https://www.ebay.com/itm/MINI-3A-DC-...0BF~:rk:3:pf:0 configured to output 3.3v
                                The monitor ran fine for three weeks like this while I waited for the correct ordered part. I suspect that it would have run indefinitly with this as well

                                Comment


                                  #17
                                  Re: Dell U2312H Repair

                                  Good evening, forgive me if I insert myself. There was a short on my power board and some components exploded. Could you indicate the values of r815 and zd801? thanks a lot..

                                  Comment


                                    #18
                                    Re: Dell U2312H Repair

                                    seems to be a common shit problem..

                                    i have one at home..... after power off the mains.... very hard to on back...
                                    need to leave on the mains for some time... around one hour to bring the monitor to on again.

                                    Comment


                                      #19
                                      Hi guys. I have this problem too with my monitor. I have one question, is it normal the voltage output and input at I301 are intermittent but are in spec?. Let say 5V input and 3.3V output are reached, but it not consistently. Drop and get again with tickling sound at power board.

                                      Sorry for my English

                                      Comment


                                        #20
                                        Re: Dell U2312H Repair

                                        Good day everyone. I had a similar problem with my dell 2212hm rev.6A. One day the monitor just wont turn on. I checked the power supply and everything was working. I did check this regulator g1084-33 and there is no voltage on the output. I replaced this regulator and my monitor is back to life. Thank your for the tips.

                                        Comment

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