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    #1

    Dead Dell 1905FP LCD monitor

    Hi,

    I have a really nice monitor that I'd like to get working. The Dell takes in line voltage (120V AC). But nothing lights up at all, not even neon lights.

    I took it apart and found three bulging capacitors. The main fuse seems to be ok. I found about 400V across the big capacitor, using an AC multimeter scale.

    Other than that I don't know how to proceed. I don't have an extra CCFL on hand.

    In the first picture below, the three caps are the ones in the foreground, left. They are 1- 820uF, 25V GF(M) (the tall one) and 2- 1000uF, 10V, U9A (the other two).

    Please let me know if there is any other info you need. Any help is appreciated.

    Blessings,
    Paul








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    #2
    Re: Dead Dell 1905FP LCD monitor

    Originally posted by paul1149 View Post
    Hi,

    I have a really nice monitor that I'd like to get working. The Dell takes in line voltage (120V AC). But nothing lights up at all, not even neon lights.

    I took it apart and found three bulging capacitors. The main fuse seems to be ok. I found about 400V across the big capacitor, using an AC multimeter scale.

    Other than that I don't know how to proceed. I don't have an extra CCFL on hand.

    In the first picture below, the three caps are the ones in the foreground, left. They are 1- 820uF, 25V GF(M) (the tall one) and 2- 1000uF, 10V, U9A (the other two).

    Please let me know if there is any other info you need. Any help is appreciated.

    Blessings,
    Paul







    With 120volts Ac in measure the voltage across the big cap...BUT DC not AC...should be about 160-170 volts ???

    Comment

      #3
      Re: Dead Dell 1905FP LCD monitor

      How about doing this the proper way? Take two pictures one of the power supply from directly overhead, and one of the back side of the power supply. For best results, they should be at least 1000 pixels on a side, but no side should be greater than 2000 pixels. Attach them using 'Manage Attachments' - below the text entry area.

      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

        #4
        Re: Dead Dell 1905FP LCD monitor

        Originally posted by paul1149 View Post
        I took it apart and found three bulging capacitors. The main fuse seems to be ok. I found about 400V across the big capacitor, using an AC multimeter scale.
        Replace ALL your electrolytic caps on the power board, and not just the bulging ones. The largest one can be left as is because it rarely, but not never, fails.

        Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

        PCBONEZ will me if I don't explain that when replacing caps, you want the same or more ripple and the same or less ESR (ohms) as per

        https://www.badcaps.net/forum/showpos...47&postcount=3

        Members here like Panasonic FR, FM, and FC series in that order.

        PS. If you live in the USA and depending if the monitor has PFC or not, DC voltages at the big cap can reach 360 to 370V DC. As Rtech says, you are measuring DC across the big cap.
        --- begin sig file ---

        If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

        We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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        Comment

          #5
          Re: Dead Dell 1905FP LCD monitor

          Awesome. Thanks very much to all for the input. Let's see if I can get this right.

          First, I checked across the big cap and it indeed looks like about 160V DC.

          Second, the new pics should be attached.

          Third, I don't know what a PFC is. I don't mind replacing all the caps, but is there some way to ascertain whether the caps are the problem here?

          Appreciate your time. I'll try to remove the previous thumbs.

          p.
          Attached Files

          Comment

            #6
            Re: Dead Dell 1905FP LCD monitor

            Originally posted by paul1149 View Post
            Third, I don't know what a PFC is.
            PFC = power factor correction

            http://en.wikipedia.org/wiki/Power_f...n-linear_loads

            I don't mind replacing all the caps, but is there some way to ascertain whether the caps are the problem here?
            Let me put it this way. Obviously bloated bad caps will NOT work.

            If you are questioning our analysis, then you can measure the uF and ESR with the proper tools as I stated in post #4.
            --- begin sig file ---

            If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

            We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

            Please do not post inline and offsite as they slow down the loading of pages.

            --- end sig file ---

            Comment

              #7
              Re: Dead Dell 1905FP LCD monitor

              I'm not questioning your analysis, I'm trying to figure out the probability of success while feeling my way through something I've never done before. I followed PlainBill's sig links, and ended up at Mouser's. They seem to have a great selection, but what do I choose for the tolerance range? The existing caps are Samxon, 105deg C8.

              Thanks,
              p.

              Comment

                #8
                Re: Dead Dell 1905FP LCD monitor

                Originally posted by paul1149 View Post
                I'm not questioning your analysis, I'm trying to figure out the probability of success while feeling my way through something I've never done before. I followed PlainBill's sig links, and ended up at Mouser's. They seem to have a great selection, but what do I choose for the tolerance range? The existing caps are Samxon, 105deg C8.

                Thanks,
                p.
                There are three ways to handle this problem.

                The first is a step by step approach. Replace the three obviously bad capacitors. If the monitor still isn't working, move on with the troubleshooting. This has the advantage of using the minimum number of components while is has the disadvantage of incurring significant shipping charges.

                A second approach is to perform some rudimentary tests before ordering any parts, then order all parts that appear to be required. This takes more time initially, but improves the chances of getting a working monitor on the first try. On the bottom of the card are labels indicating the voltages out of the supply. With power on, carefully measure the voltage on each of these pins, using the pins labeled GND as a reference.

                The pictures leave a lot to be desired. The easiest way to get better pictures is to turn off the flash and take the pictures near a window on a sunny day.

                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

                  #9
                  Re: Dead Dell 1905FP LCD monitor

                  Thanks, that was helpful. I decided to stay in-house here, to order Rubycons, and to try the incremental approach.

                  I just checked those output voltages, and all the Ground, 12V and 5V terminals are registering fine. I'm getting nothing from the On/Off, Ready, and DIM terminals, but I'm not sure I should. I have the power board detached from everything else but the line voltage.

                  Lacking any contradictory indications here, I'm going to order the three bulging caps tomorrow.

                  I did try to take pics without flash, but they came out reddish. I didn't try with a natural light source.

                  p.

                  Comment

                    #10
                    Re: Dead Dell 1905FP LCD monitor

                    note whem replacing the caps check
                    C112 it should be a 2.2uF 50v
                    some came out of factory with wrong part ( 22uF 50v)
                    replace this cap along with the otheres that have bulged

                    Comment

                      #11
                      Re: Dead Dell 1905FP LCD monitor

                      Originally posted by paul1149 View Post
                      Thanks, that was helpful. I decided to stay in-house here, to order Rubycons, and to try the incremental approach.

                      I just checked those output voltages, and all the Ground, 12V and 5V terminals are registering fine. I'm getting nothing from the On/Off, Ready, and DIM terminals, but I'm not sure I should. I have the power board detached from everything else but the line voltage.

                      Lacking any contradictory indications here, I'm going to order the three bulging caps tomorrow.

                      I did try to take pics without flash, but they came out reddish. I didn't try with a natural light source.

                      p.
                      The fact that you are getting those two voltages is a good sign. You are correct, the other voltages are sourced from the signal card.

                      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: Dead Dell 1905FP LCD monitor

                        Thanks, but I don't see a C112. On the back I see the solder points for C110 and C111, but they are under the big cap, and I don't see anything corresponding to them on the face of the board.

                        Comment

                          #13
                          Re: Dead Dell 1905FP LCD monitor

                          Gentlemen,

                          Observe your handiwork. I got the three caps today, and put them in this evening. The hardest thing by far was remembering how this thing went together. Next time I think I will need to put the machine together as I await the parts.

                          But aside from that the job went very easily. Amazingly so, actually. Many thanks for your insightful guidance. We now have another monitor at our disposal.

                          THANK YOU,
                          p.
                          Attached Files

                          Comment

                            #14
                            Re: Dead Dell 1905FP LCD monitor

                            Originally posted by paul1149 View Post
                            Gentlemen,

                            Observe your handiwork. I got the three caps today, and put them in this evening. The hardest thing by far was remembering how this thing went together. Next time I think I will need to put the machine together as I await the parts.

                            But aside from that the job went very easily. Amazingly so, actually. Many thanks for your insightful guidance. We now have another monitor at our disposal.

                            THANK YOU,
                            p.
                            Congratulations.

                            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

                              #15
                              Re: Dead Dell 1905FP LCD monitor

                              Originally posted by retiredcaps View Post
                              https://www.badcaps.net/forum/showpos...47&postcount=3
                              Sorry, correct link is (for future people)

                              https://www.badcaps.net/forum/showpo...47&postcount=3
                              --- begin sig file ---

                              If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                              We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                              Please do not post inline and offsite as they slow down the loading of pages.

                              --- end sig file ---

                              Comment

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