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    Dell 2000FP Blank screen problem

    Hi,

    I have a Dell 2000FP LCD monitor.

    Problem description:
    When i power up the monitor the green led comes on and stays on but there is no picture shown.

    I am enclosing pictures of the boards (see enclosed pics).
    Overall => Shows both inverter board and main board

    Inverter_Pic=>Shows pic of inverter. Shows pad numbering for transformers. Note: I think pad1 of transformer is denoted by "yellow" dot.

    Mag_Invert_1=>Close up of left side of inverter
    Mag_Invert_2=>Close up of middle of inverter
    Mag_Invert_3=>Close up of right side of inverter




    What i have done thus far:
    1-With the power on i shine a flash-light onto the screen. I can see a faint image. So this tells me from past experience that its probably either the bulbs or inverter board.

    2-I checked each of the 6 bulbs with my "home-made" bulb tester. They all appear to be "good" bulbs.

    3-I also measured the transformer using DVM:
    Note: Transformer was "in-circuit" for these measurements.

    Transformer A:
    Pin1_to_Pin8: 3.88Mohm
    Pin1_to_Pin9: 3.88Mohm
    Pin1_to_Pin10: 3.88Mohm
    Pin1_to_Pin11: 3.88Mohm
    Pin2_to_Pin8: 6.15Kohm
    Pin2_to_Pin9: 6.15Kohm
    Pin2_to_Pin10: 6.15Kohm
    Pin2_to_Pin11: 6.15Kohm
    Pin3_to_Pin8: 6.13Kohm
    Pin3_to_Pin9: 6.13Kohm
    Pin3_to_Pin10: 6.13Kohm
    Pin3_to_Pin11: 6.13Kohm
    Pin4_to_Pin8: 6.11Kohm
    Pin4_to_Pin9: 6.11Kohm
    Pin4_to_Pin10: 6.11Kohm
    Pin4_to_Pin11: 6.11Kohm
    Pin5_to_Pin8: 6.08Kohm
    Pin5_to_Pin9: 6.08Kohm
    Pin5_to_Pin10: 6.08Kohm
    Pin5_to_Pin11: 6.08Kohm
    Pin6_to_Pin8: 3.84Mohm
    Pin6_to_Pin9: 3.84Mohm
    Pin6_to_Pin10: 3.84Mohm
    Pin6_to_Pin11: 3.84Mohm
    Pin7_to_Pin8: 199.2ohm
    Pin7_to_Pin9: 199.2ohm
    Pin7_to_Pin10: 199.2ohm
    Pin7_to_Pin11: 199.2ohm


    Transformer B:
    Pin1_to_Pin8: Open
    Pin1_to_Pin9: Open
    Pin1_to_Pin10: Open
    Pin1_to_Pin11: 3.8Mohm
    Pin2_to_Pin8: Open
    Pin2_to_Pin9: Open
    Pin2_to_Pin10: Open
    Pin2_to_Pin11: 5.91Kohm
    Pin3_to_Pin8: Open
    Pin3_to_Pin9: Open
    Pin3_to_Pin10: Open
    Pin3_to_Pin11: 5.11Kohm
    Pin4_to_Pin8: Open
    Pin4_to_Pin9: Open
    Pin4_to_Pin10: Open
    Pin4_to_Pin11: 5.91Kohm
    Pin5_to_Pin8: Open
    Pin5_to_Pin9: Open
    Pin5_to_Pin10: Open
    Pin5_to_Pin11: 5.88kOhm
    Pin6_to_Pin8: Open
    Pin6_to_Pin9: Open
    Pin6_to_Pin10: Open
    Pin6_to_Pin11: 3.8Mohm
    Pin7_to_Pin8: Open
    Pin7_to_Pin9: Open
    Pin7_to_Pin10: Open
    Pin7_to_Pin11: 199.2ohm


    NOte: If there is a better way to show this data in a tabular format let me know.




    4-I also measure the voltages present on the connector.
    Pin8: 19.75V
    Pin7: 19.75V
    Pin6:19.75V
    Pin5: 0V
    Pin4: 0V
    Pin3: 0V
    Pin2: 1.972V
    Pin1: 3.279V




    Basically i would like some input on what to try/do next. From above is the transformer "bad"? Also, any inputs / suggestions you can give please let me know.

    NOte: I was planning to re-solder the transformer connections but i wanted to post what i have done thus far.
    Attached Files

    #2
    Re: Dell 2000FP Blank screen problem

    Rather than resolder the transformers at this point, there are a couple of things to do first.

    1. Check the fuse

    2. Check Q5, Q6, Q13 and it's companion, (probably Q12) to see if any are shorted.

    3. If no transistors are shorted, remove one of the transformers and repeat the measurements. I would prefer measurements in this pattern

    1 to 2, 1 to 3, 1 to 4, 1 to 5, 1 to 6, 1 to 7, 1 to 8, 1 to 9, 1 to 10, 1 to 11

    2 to 3, 2 to 4, 2 to 5, 2 to 6, 2 to 7, 2 to 8, 2 to 9, 2 to 10, 2 to 11

    3 to 4, 3 to 5, 3 to 6, etc

    4 to 5, 4 to 6, etc

    5 to 6, etc

    etc,

    etc until finally

    9 to 10, 9 to 11

    10 to 11

    For this purpose 3.88 Mohms is essentially open. Just say 'open' or use a dash (-) for anything over 100Kohm.

    What I would expect to see is the pins on the primary side appear connected in pairs, perhaps 1 to 7, 2 to 3, 5 to 6. On the secondary side I would expect to see two pairs.

    4. A picture of the back of the inverter board.

    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: Dell 2000FP Blank screen problem

      I had a 15 inch Dell monitor that was laid out just like this one. There is a surface mount fuse on the inverter board (F1 near the white connector) that may be blown.
      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

      Comment


        #4
        Re: Dell 2000FP Blank screen problem

        I checked the fuse......its a short measures about 0.2 or 0.3ohm.

        For the transistors. Any idea if they are mosfets or bi-polars? Any idea on data sheet? Or if you want i can measure resistances and diode-checks across all leads. Would this suffice?

        Note: Transistors have marking of DT and QX on them.

        Comment


          #5
          Re: Dell 2000FP Blank screen problem

          Originally posted by Welchs101
          I checked the fuse......its a short measures about 0.2 or 0.3ohm.

          For the transistors. Any idea if they are mosfets or bi-polars? Any idea on data sheet? Or if you want i can measure resistances and diode-checks across all leads. Would this suffice?

          Note: Transistors have marking of DT and QX on them.
          They are bipolar transistors. This is the same circuit used in the Dell 1703 monitors. Just check the resistance between each set of pins. For Q5 and Q6 measure from the pin on the upper left to the pin on the right. Then measure from the upper left to the lower left. Then measure from the lower left to the pin on the right. If a transistor is shorted it will read less than 10 ohms.

          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: Dell 2000FP Blank screen problem

            I measured the resistance of the Q5, Q6 and Q12,Q13 transistors. See data below. See enclosed pic for reference.

            Q5:
            Pin1-Pin2: 3.86MegOhm
            Pin1-Pin3: 3.9MegOhm
            Pin2-Pin3: 6kOhm (note: black lead pin2, red lead pin3)


            Q6:
            Pin1-Pin2: 3.89MegOhm
            Pin1-Pin3: 3.89MegOhm
            Pin2-Pin3: 5.83kOhm (note: black lead pin2, red lead pin3)

            Q12:
            Pin1-Pin2: 3.89MegOhm
            Pin1-Pin3: 3.84MegOhm
            Pin2-Pin3: 5.78kOhm (note: black lead pin2, red lead pin3)


            Q13:
            Pin1-Pin2: 3.88MegOhm
            Pin1-Pin3: 3.84MegOhm
            Pin2-Pin3: 5.75kOhm (note: black lead pin2, red lead pin3)
            Attached Files

            Comment


              #7
              Re: Dell 2000FP Blank screen problem

              Originally posted by Welchs101
              I measured the resistance of the Q5, Q6 and Q12,Q13 transistors. See data below. See enclosed pic for reference.

              Q5:
              Pin1-Pin2: 3.86MegOhm
              Pin1-Pin3: 3.9MegOhm
              Pin2-Pin3: 6kOhm (note: black lead pin2, red lead pin3)


              Q6:
              Pin1-Pin2: 3.89MegOhm
              Pin1-Pin3: 3.89MegOhm
              Pin2-Pin3: 5.83kOhm (note: black lead pin2, red lead pin3)

              Q12:
              Pin1-Pin2: 3.89MegOhm
              Pin1-Pin3: 3.84MegOhm
              Pin2-Pin3: 5.78kOhm (note: black lead pin2, red lead pin3)


              Q13:
              Pin1-Pin2: 3.88MegOhm
              Pin1-Pin3: 3.84MegOhm
              Pin2-Pin3: 5.75kOhm (note: black lead pin2, red lead pin3)
              OK, those aren't shorted.

              On the inverter, CN1, pins 7 and 8 are the brightness control and On/Off. See if those change state when you push the power button.

              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


                #8
                Re: Dell 2000FP Blank screen problem

                I measured the pins on the connector CN1. But instead of measuring CN1 i measured the connector pins on the main board which are then tied to the connector CN1 on the inverter board.

                Using the pin designation from one of my earlier pics (also included here) i measured the following:
                Pins 8,7,6: Off=>19.83V, On=>19.75V

                Pins 5,4,3: Off=>0V , On=>0.002V

                Pin2: Off=> 1.963V , On=> 1.971V

                Pin1: Off=>0V, On=>3.279V



                Note: Not sure if this is significant or not but the very first time i turned monitor on when measuring pin8 i actually saw an image for a split second and then it went away.
                Attached Files

                Comment


                  #9
                  Re: Dell 2000FP Blank screen problem

                  Originally posted by Welchs101
                  I measured the pins on the connector CN1. But instead of measuring CN1 i measured the connector pins on the main board which are then tied to the connector CN1 on the inverter board.

                  Using the pin designation from one of my earlier pics (also included here) i measured the following:
                  Pins 8,7,6: Off=>19.83V, On=>19.75V

                  Pins 5,4,3: Off=>0V , On=>0.002V

                  Pin2: Off=> 1.963V , On=> 1.971V

                  Pin1: Off=>0V, On=>3.279V



                  Note: Not sure if this is significant or not but the very first time i turned monitor on when measuring pin8 i actually saw an image for a split second and then it went away.
                  That looks like the control signal is working. I believe you are numbering backwards. I saw what appeared to be a number 1 by the right hand pin.

                  That 'image for a split second' is significant. There is a vast difference between troubleshooting 'dead backlights' and 'two seconds to black' problems.

                  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


                    #10
                    Re: Dell 2000FP Blank screen problem

                    The "2 seconds to black" only occurred once out of 15 tries and it was the first time i turned it on this morning. I have not seen it any other time even on first tries. Not saying its not "2 seconds to black" it could be but i have seen the 2 seconds to black before and this just did not seem like it.......but i dont rule anything out.

                    SHould i now remove the transformers or do somethign else?

                    Comment


                      #11
                      Re: Dell 2000FP Blank screen problem

                      Originally posted by Welchs101
                      The "2 seconds to black" only occurred once out of 15 tries and it was the first time i turned it on this morning. I have not seen it any other time even on first tries. Not saying its not "2 seconds to black" it could be but i have seen the 2 seconds to black before and this just did not seem like it.......but i dont rule anything out.

                      SHould i now remove the transformers or do somethign else?
                      The delay time on the 'two seconds to black' can vary. I've seen some where it is just a very brief flash - didn't even reach full brightness. Yes, go ahead and remove the two transformers and compare resistances out of circuit.

                      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: Dell 2000FP Blank screen problem

                        Well, I THINK IT MIGHT BE FIXED!!!!!!!!!!!!!

                        I remember something Bill said when i was working on some other monitor about "resoldering" the leads of the transformer. So before removing the transformer (which is hard for me......soldering not my strongest thing) i decided to just add additional solder to the transformer leads. I also added solder to the bypass caps that are next to the transformer cause they looked like they could use it. I did this.........then plugged in the power.......and the monitor came to life. I get the monitor no connection screen which i did not get before.

                        So thanks BILL! You helped fix another one. Glad your back! Even more glad your ok.

                        I will probably add a little more solder to the transformer just to be sure i added enough.

                        Comment


                          #13
                          Re: Dell 2000FP Blank screen problem

                          Originally posted by Welchs101 View Post
                          Well, I THINK IT MIGHT BE FIXED!!!!!!!!!!!!!

                          I remember something Bill said when i was working on some other monitor about "resoldering" the leads of the transformer. So before removing the transformer (which is hard for me......soldering not my strongest thing) i decided to just add additional solder to the transformer leads. I also added solder to the bypass caps that are next to the transformer cause they looked like they could use it. I did this.........then plugged in the power.......and the monitor came to life. I get the monitor no connection screen which i did not get before.

                          So thanks BILL! You helped fix another one. Glad your back! Even more glad your ok.

                          I will probably add a little more solder to the transformer just to be sure i added enough.
                          I am having a similar issue as you had. Did it look like you needed to do some re-soldering on your board or was it just something you decided to try?

                          Comment


                            #14
                            Re: Dell 2000FP Blank screen problem

                            dose anyone know the specs. on the Dt transistors for Q5 Q6 Q12 and Q13
                            Thanks Al.
                            Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                            Comment


                              #15
                              Re: Dell 2000FP Blank screen problem

                              Originally posted by alexanna View Post
                              dose anyone know the specs. on the Dt transistors for Q5 Q6 Q12 and Q13
                              Thanks Al.
                              Look 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


                                #16
                                Re: Dell 2000FP Blank screen problem

                                Thanks, PlainBill
                                Al.
                                Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                Comment


                                  #17
                                  Re: Dell 2000FP Blank screen problem

                                  Thanks for all the good advice here. Can anyone help me on the rating of the SMT fuse F1? It is marked "FT". According to my Google searches it can be anything from 0.5A to the sound it makes when it blows...
                                  Attached Files

                                  Comment


                                    #18
                                    Re: Dell 2000FP Blank screen problem

                                    Originally posted by Loom View Post
                                    Thanks for all the good advice here. Can anyone help me on the rating of the SMT fuse F1? It is marked "FT". According to my Google searches it can be anything from 0.5A to the sound it makes when it blows...
                                    It would help to know where the fuse is used. I'm used to seeing SMD fuses on inverters, but .5A is too low, unless it's only for the inverter controller.

                                    Also of interest, the references I've found (Littlefuse) shows their .5A slow blow fuse is marked TF. So another possibility is this is a fast acting 6.3A fuse.

                                    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


                                      #19
                                      Re: Dell 2000FP Blank screen problem

                                      It's on the inverter board of a Dell 2000FP, as shown on the attached picture I stole from the first post.
                                      Attached Files

                                      Comment


                                        #20
                                        Re: Dell 2000FP Blank screen problem

                                        I don't understand why it is soooo hard to find a fuse marking guide for these. It's like it's a big secret or something.

                                        These questions are all over the net, and NO ONE has a definitive answer...
                                        veritas odium parit

                                        Comment

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