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DELL 2007wfp - 2 Secs to black w/flickering

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    DELL 2007wfp - 2 Secs to black w/flickering

    Hi,i bought this monitor in late 2009, used,its from 2007.
    im a happy owner since then.

    lt has never been too bright, so i used the brightness at 66-100
    doing that result in a whine(high frecuency sound). so i tried to use it at 50, just for precaution.
    for 2 years no problems

    A week ago, after using mi monitor for a couple of hours,i moved it to my desk(it was in a chair) and get out.
    several hours later i power on and the image lasted 1 minute. then no backlight(but stayed gren light on)

    if i unplugged it and waited a bit, it lasts 30-40 secs

    if i try to re power on its 2 secs to black.
    ----
    so i decided to take a look,and see if i could do something.

    my first thought: PSU related problem
    so i changed al the electrolytics. except the huge one
    tested diodes, the mosfet(sk3548), resolded critical sectors.
    all seemed okay, no bulging capacitor or cold joints of solder.

    tested and it was the same.. first time lasted 30 secs then it was 2 secs to black.
    when it lasted 30 secs, i saw a flickering every 3 or 4 seconds.
    ------
    so i looked further into the inverter, changed all the electrolytics an resoldered transformers.

    no changes.

    i also tried to power on the monitor with 1 or two of the 4 ccfl conectors, nothing
    ---------
    i have dissasembled the LCD panel now and have access to the tubes.(photos)

    should i recap all the boards?? i have crappy Trec `s capacitors, but they are new

    what should i do?


    Many thanks in advance, sorry for grammar errors(tell me so i can correct them)
    cheers from argentina

    PD,
    1 i have done most of the 2 sects to black excellent tutorial, except th tranformer part.

    2 im sorry if its to large i can resume it and put spoilers.
    Attached Files
    Last edited by Armandorf; 03-15-2012, 12:51 AM. Reason: photos added

    #2
    Re: DELL 2007wfp - 2 Secs to black w/flickering

    tubes photos,

    i have another monitor, LG with a broken panel, so i have a test inveersor and tubes,no?

    its a 19 screen, its compatible to test dell tubes with the LG?.

    here i found a lot of infomation, great forum, keep it up
    Attached Files

    Comment


      #3
      Re: DELL 2007wfp - 2 Secs to black w/flickering

      Originally posted by Armandorf View Post
      i also tried to power on the monitor with 1 or two of the 4 ccfl conectors, nothing
      The inverter PWM will shutdown all the ccfls if one or more of them are not connected. Either all the ccfls work or none at all.

      Many thanks in advance, sorry for grammar errors(tell me so i can correct them)
      cheers from argentina
      Your written English is better than most who are native speakers.


      1 i have done most of the 2 sects to black excellent tutorial, except th tranformer part.
      Measure the resistance between pins 1-8 and 4-5 for all 3 transformers. You should have 6 readings. Post your results. They should be within 3% of each other. I expect readings in the 1023 ohm range.

      PS. Those are excellent photos.
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        #4
        Re: DELL 2007wfp - 2 Secs to black w/flickering

        Originally posted by Armandorf View Post
        i have another monitor, LG with a broken panel, so i have a test inveersor and tubes,no?

        its a 19 screen, its compatible to test dell tubes with the LG?.
        Yes, you can use these ccfls as "known good" to test with your Dell despite the size difference.
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          #5
          Re: DELL 2007wfp - 2 Secs to black w/flickering

          transformers readings, pins numbered as described in attachment.
          with the tranformers mounted in the board.( no need for desoldering?)

          DMM set in the closest scale, in this case 2K ohm

          1rst transf.-
          average resistance 1.062K-
          1%= 10.62 ohms

          1-8 resistance: 1.061 K (deviation -0.16%)
          4-5 resistance: 1.063 K (deviation +0.16%)

          2nd transf

          average 1.0665K
          1%=10.66 ohms

          1-8 resistance: 1.064 K( - 0.21%)
          4-5 resistance: 1.069 K(+ 0.25%)

          3rd transf

          1-8 resistance: 1.040 K
          4-5 resistance: 52.3 K(200K scale)

          with a transformer replacement should work? can i emulate this tranformer to see if i have another problem?

          i will read the components relationed with these pins

          thanks
          Last edited by Armandorf; 03-15-2012, 01:50 PM.

          Comment


            #6
            Re: DELL 2007wfp - 2 Secs to black w/flickering

            Originally posted by Armandorf View Post
            3rd transf

            1-8 resistance: 1.040 K
            4-5 resistance: 52.3 K(200K scale)

            with a transformer replacement should work?
            Transformer #3 is bad. It has an open winding.

            See the following for a replacement. They are available on ebay.

            https://www.badcaps.net/forum/showthread.php?t=17945

            http://www.ebay.com/sch/i.html?_from...All-Categories

            It is highly unlikely that another replacement transformer will work. The number of turns is very specific to each board.
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              #7
              Re: DELL 2007wfp - 2 Secs to black w/flickering

              thanks for the information,
              what about the tubes, theres a slight blackness in the ends, should they work a couple of years more?

              im desoldering the transformer to see it from the other side, luckili it can be open near the pin.

              im a bit nervous about shopping from ebay to argentina, i will research.

              also tested other components all readings qhere equal with the other pair of transformers. did the same for mosfets on usb board

              in the logic board, i find the caps slightly bulged, its better leave them as it is, or replace all of them?

              i want to make a whole service to the monitor, i love this monitor,thats why i want to leave it as new as possible. here is difficult to find non TN panels monitors

              Comment


                #8
                Re: DELL 2007wfp - 2 Secs to black w/flickering

                Originally posted by Armandorf View Post
                what about the tubes, theres a slight blackness in the ends, should they work a couple of years more?
                They look okay, but sometimes the return wire (the thinner guage) can become disconnected/charred/frayed. You can't see it because it is inside of the silicon cap end. Replace the transformer first and retest. I expect it will work fine and the caps and the transformers were the only bad things.

                im a bit nervous about shopping from ebay to argentina, i will research.
                My experience with China based sellers have been mainly positive. They are quick to correct mistakes.

                in the logic board, i find the caps slightly bulged, its better leave them as it is, or replace all of them?
                Any cap that is slightly bulged is automatically bad. We recommend the standard advice (regulars may skip)

                https://www.badcaps.net/forum/showpo...84&postcount=3

                edit: If you are talking about the green Lelon caps by the connector on the logic board they look completely flat to me in one angled picture. The caps on the logic board don't undergo the same stress as those on the power board.
                Last edited by retiredcaps; 03-15-2012, 04:33 PM. Reason: took another look at the pics
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                  #9
                  Re: DELL 2007wfp - 2 Secs to black w/flickering

                  sorry i abandoned this thread for a long long time, thanks for the help, and i hope that this photos and information to be helpful in the future.

                  i had many issues with my mailing from china ebay, hopefully in 3 weeks will be arriving the little transformer.

                  if anyone needs a photo of some board of the
                  monitor i can post it.

                  Comment


                    #10
                    Re: DELL 2007wfp - 2 Secs to black w/flickering

                    yesterday arrived the transformer. it had SMD pins, so i put short wires(ends of used caps or resistences), soldered and mounted the transformer on the inverter.

                    i tested
                    but i still have the same problem; it flashes very quickly and i can see the [ No signal OSD] for a fraction of a second

                    i re checked the 6 ccfl´s with an inverter from a Lg 19'' and they flash once,1 second off, and lit on again, this time with an increasing brightness during the first 3 seconds .finally they still hang on with no noticeable problems.

                    Comment


                      #11
                      Re: DELL 2007wfp - 2 Secs to black w/flickering

                      You are saying that this replacement transformer has surface mounted pins instead of the through hole pins. Does it have the same part number as the original and did you take any resistance reading to see if it is the same as the original good transformer?
                      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


                        #12
                        Re: DELL 2007wfp - 2 Secs to black w/flickering

                        Originally posted by Armandorf View Post
                        yesterday arrived the transformer.
                        Did you measure the resistance of the new transformer before installing it? If no, what is the measurement?

                        edit: budm beat me by 2 minutes.
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                          #13
                          Re: DELL 2007wfp - 2 Secs to black w/flickering

                          yes, the readings were 1.054K and 1.055K, and the readings in this transformer are equal to the other two.

                          looking the power supply, i searched for bad diodes or smd transistor shorted(continuity test)
                          and found something

                          i have 19.2v dc
                          an other 3 pins with 3.3v, 0,8v , 0v(it seems 2,5 mV with the tester in 200mV scale)

                          the last pin has no voltage but it doesnt seem grounded(continuity test with chassis marks open)

                          posted an edited pic of the solder layer for the voltages in the power supply

                          where i cand find a diagram for this power supply?
                          i will be looking for dead voltage regulators in the other boards, i read thats quite common.
                          Attached Files
                          Last edited by Armandorf; 07-25-2012, 08:05 PM. Reason: photo added

                          Comment


                            #14
                            Re: DELL 2007wfp - 2 Secs to black w/flickering

                            Your power supply is OK, it is only a single output supply, 19VDC, this 19V is coverted down to lower volltage to run the logic board, the inverter runs off the 19V directly. Your problem is more likely to be in the Inverter board. Does the new transformer 4 middle pins of the transformer all have low Ohm reading?
                            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 2007wfp - 2 Secs to black w/flickering

                              what do you mean with low ohm readings? in which pins I should measure?
                              in the pcb the 2 central pins of each side are joined

                              Comment


                                #16
                                Re: DELL 2007wfp - 2 Secs to black w/flickering

                                Originally posted by Armandorf View Post
                                what do you mean with low ohm readings? in which pins I should measure?
                                in the pcb the 2 central pins of each side are joined
                                Budm is asking you to measure P1 to P2 and P3 to P4. See diagram below. It is not a 4001R, but the 4001K is "close enough".

                                http://www.lcdparts.net/TransformerD...ProductID=2725
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                                  #17
                                  Re: DELL 2007wfp - 2 Secs to black w/flickering

                                  Thanks retiredcaps for clarifying my question. This transformer has two Primary windings and two secondary high voltage windings. Just want to make sure the new transformer has the same windings as the original one.
                                  Last edited by budm; 07-26-2012, 12:03 AM.
                                  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


                                    #18
                                    Re: DELL 2007wfp - 2 Secs to black w/flickering

                                    PS. It would also help if you posted a picture of your new transformer and jumper leads.
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                                    Please do not post inline and offsite as they slow down the loading of pages.

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                                    Comment


                                      #19
                                      Re: DELL 2007wfp - 2 Secs to black w/flickering

                                      i measured p1to p2 and p3 to p4. both readings marks open

                                      i read that the 4001 was the important part of the transformer, i have a wrong transformer? i cant find the exact model en ebay
                                      Attached Files

                                      Comment


                                        #20
                                        Re: DELL 2007wfp - 2 Secs to black w/flickering

                                        The board that I have here in front of me has two transformers with P/N 4001R702048, the middle transformer has P/N 4001R703038. When you told us the replacement was the surface mounted type, then I kind of suspect that it is not the same transformer as original.
                                        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

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