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Dell 2407WFPb Monitor - Bad Cap

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    Re: Dell 2407WFPb Monitor - Bad Cap

    I'm going to purchase a multimeter for next week when I attempt to repair this little bad boy. Anyway, the real question is: once I have a multimeter how do I use it?

    I put one lead on one end of the cap/resistor/etc and the other lead on the other end and the screen should read what? And I assume I can do this with all parts I suspect to be bad or are there special instructions for certain pieces? Lastly, if the capacitor is standing and i can't measure from the top, I can flip the board around and use the same endpoints on the bottom of the board to get the read correct?

    Comment


      Re: Dell 2407WFPb Monitor - Bad Cap

      you should find instructions to test the single parts by query google for "check transistor" (e.g.).

      what you can do easily with the multimeter on "beep"-setting (makes a beep if theres no/very little resistance in the part. Marked with some kind of speaker symbol):

      Transistor
      check all possible three combinations of the "foots", if anyone beeps -> broken

      Diode
      in both ways beep (switch the needles) -> broken

      Fuse
      no beep -> broken

      Cap
      possible, but i don´t know how. The multimeter has to have a special function for this. I don´t even know if mine is having it.

      Resistance is easy, when you know, with value it should have. If the multimeter tilts on highest range, its broken

      You can turn the PCB around and test on the endpoints, yes. All checks on unplugged board!

      Comment


        Re: Dell 2407WFPb Monitor - Bad Cap

        Thats just what I needed to get started. Thanks!

        Comment


          Re: Dell 2407WFPb Monitor - Bad Cap

          ok, now i´ve changed the 120uF cap (to a 150uF 400V 105°), the resistor, the 3502 MOSET (to a P10NK60Z) and the fuse.

          After plugging in an switching on (the power board alone) there was a really beautiful blue-white flash and than i sat in the dark (it is nearly 9PM here).

          the fuse melted, but the new parts are still ok. So i guess here the real challenge begins...

          edit:
          i just talked to my uncle who is an absolute professional in e-technics (designing & building his own hifi amps for fun e.g.) and he told me two things:
          - it´s nearly sure that the real problem lies within the trafo (one of those coils), and it´s nearly impossible to find replacement
          - buy a new monitor

          my work ends here. i´ll put the pieces in a box and search the internets again in 6 months or so. If nobody found a solution until then (or new power boards pop up somewhere) the whole box will face it´s final destination.
          Last edited by Tyan; 09-29-2011, 01:19 PM.

          Comment


            Re: Dell 2407WFPb Monitor - Bad Cap

            Originally posted by Tyan View Post
            ok, now i´ve changed the 120uF cap (to a 150uF 400V 105°), the resistor, the 3502 MOSET (to a P10NK60Z) and the fuse.

            After plugging in an switching on (the power board alone) there was a really beautiful blue-white flash and than i sat in the dark (it is nearly 9PM here).

            the fuse melted, but the new parts are still ok. So i guess here the real challenge begins...

            edit:
            i just talked to my uncle who is an absolute professional in e-technics (designing & building his own hifi amps for fun e.g.) and he told me two things:
            - it´s nearly sure that the real problem lies within the trafo (one of those coils), and it´s nearly impossible to find replacement
            - buy a new monitor

            my work ends here. i´ll put the pieces in a box and search the internets again in 6 months or so. If nobody found a solution until then (or new power boards pop up somewhere) the whole box will face it´s final destination.
            With all respect to your uncle, he is almost certainly wrong. A failure of the SMPS transformer is very, very rare. It is much more likely the problem is the SMPS controller, or one of the components associated with the drive signal to the power FET.

            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


              Re: Dell 2407WFPb Monitor - Bad Cap

              referring to the other thread about this problem you think its the IC601 shown in this pic?



              this one looks factory new on my board... but nevertheless, if somebody could tell me, where i get one of these NCP1200A60-200A6 i´ll give it a try!

              anyway i´ll buy a new monitor
              Last edited by Tyan; 09-30-2011, 12:35 AM.

              Comment


                Re: Dell 2407WFPb Monitor - Bad Cap

                Originally posted by Tyan View Post
                referring to the other thread about this problem you think its the IC601 shown in this pic?


                this one looks factory new on my board... but nevertheless, if somebody could tell me, where i get one of these NCP1200A60-200A6 i´ll give it a try!

                anyway i´ll buy a new monitor
                The NCP1200A is available on eBay for under $6.00, including shipping. The L6561D is also available from the same seller, and at the same net cost.

                If the one on the board does in fact have a hole in the top, that would explain the fuse blowing. I STILL don't have a good handle on the operation of the PFC circuit, but looking at figure 7 of the datasheet, the FET is directly across the rectified mains voltage. When the resistor blew, the L6561D would take the hit.

                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


                  Re: Dell 2407WFPb Monitor - Bad Cap

                  this is a bit too much for my electronic knowledge :-/ i´ll see if i can get them via eBay, fumble them on my board and then let´s see, if that helps. Should have bought more fuses, only 1 left :-/

                  Comment


                    Re: Dell 2407WFPb Monitor - Bad Cap

                    Originally posted by Tyan View Post
                    this is a bit too much for my electronic knowledge :-/ i´ll see if i can get them via eBay, fumble them on my board and then let´s see, if that helps. Should have bought more fuses, only 1 left :-/
                    One trick I use in situations like this is to replace the fuse with a incandescent light bulb. If the light bulb comes on and glows brightly, something is shorted. If it flashes bright for a second, then glows dimly, there is no short.

                    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


                      Re: Dell 2407WFPb Monitor - Bad Cap

                      thanks for that light bulp trick!

                      i´ve ordered them both via eBay in china. They´re 3,90$ each + 3$ shipping btw. and ~20 days delivery til they´re here in germany...

                      Comment


                        Re: Dell 2407WFPb Monitor - Bad Cap

                        Originally posted by newbie1 View Post
                        It seems like my faulty power board has more faulty components then those stated in Post #77. I tried to purchase the whole board from Taobao.com, as being shared above, but they are ALL out of stock. So back to ordering & replacing the faulty components one-by-one..

                        Now I need your help, guys!!..

                        In addition to post #77, i had another SMD resistor R623 faulty as well.. I think it is tied to one of the leg of Q601 (shorted as well). But the problem is i could not see clearly the marking on it. Kindly see the attachments.. From what i can tell it is 4(?)7.. But i can't be sure. SO, i will need some expert help what the resistance i should order to replace the burnt resistor.. I have not yet completely check the rest of the zeners/diodes.. Hopefully, there would not be more being 'shot'.
                        update.

                        Replaced both LD6561D & NCP1200D, together with
                        1) C605 120uF/450V
                        2) Q651 STP10NK60ZFP,
                        3) R669 1k ohms SMD
                        4) Q601 2SK3548
                        5) ZD601 15V 0.5W Zener diode
                        6) R623 4.7ohms (4R7) SMD
                        7) R670 & R615 (0.22ohms)

                        Did the 'bulb test'. It light up for a fraction & goes-off... Ok good, so i thought.. Smelling success, here...

                        Replaced the Main Fuse. Hit the Power switch. DA*N IT!! IT DOESN'T light up. Sigh!. But the good thing is the 'popping' of the resistor has stopped.

                        So back to square one. Upon measuring some of the diode, found out that Q654 pins C-B-E are all shorted to each other (0 ohms). Pin C is tied to a capacitor linking to the Pin 8 (VCC) of the L6565D. But i am not sure what type of diode it is..
                        What i can see on the top of the Q654 is marked ZA with a 16 or 9L at the side (not really sure though). Package width is approx 3mm. Pictures attached

                        Any thoughts what it is?..
                        Attached Files

                        Comment


                          Re: Dell 2407WFPb Monitor - Bad Cap

                          Originally posted by newbie1 View Post
                          update.

                          Replaced both LD6561D & NCP1200D, together with
                          1) C605 120uF/450V
                          2) Q651 STP10NK60ZFP,
                          3) R669 1k ohms SMD
                          4) Q601 2SK3548
                          5) ZD601 15V 0.5W Zener diode
                          6) R623 4.7ohms (4R7) SMD
                          7) R670 & R615 (0.22ohms)

                          Did the 'bulb test'. It light up for a fraction & goes-off... Ok good, so i thought.. Smelling success, here...

                          Replaced the Main Fuse. Hit the Power switch. DA*N IT!! IT DOESN'T light up. Sigh!. But the good thing is the 'popping' of the resistor has stopped.

                          So back to square one. Upon measuring some of the diode, found out that Q654 pins C-B-E are all shorted to each other (0 ohms). Pin C is tied to a capacitor linking to the Pin 8 (VCC) of the L6565D. But i am not sure what type of diode it is..
                          What i can see on the top of the Q654 is marked ZA with a 16 or 9L at the side (not really sure though). Package width is approx 3mm. Pictures attached

                          Any thoughts what it is?..
                          ZA crosses to a diode. 2A is a 3906 equivalent PNP transistor. Information is here (follow the Marking SMD link).

                          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


                            Re: Dell 2407WFPb Monitor - Bad Cap

                            yep, same here. And the "big" Cap next to it (C620) is also toast.

                            Comment


                              Re: Dell 2407WFPb Monitor - Bad Cap

                              Just go 3 pages back, the solution is there for you!
                              https://www.badcaps.net/forum/showpo...3&postcount=77
                              I did those steps on a 4H.L2K02.A01 board, and it's working now! Had the same problems with the burned resistor. Thanks's btw endor!!!! Had to order the parts but it works like a charm, now.

                              Comment


                                Re: Dell 2407WFPb Monitor - Bad Cap

                                Originally posted by PlainBill View Post
                                ZA crosses to a diode. 2A is a 3906 equivalent PNP transistor. Information is here (follow the Marking SMD link).

                                PlainBill
                                Thanks PlainBill!. Splendid website!!.. I wish i could say the same for my current repair though.

                                Update. Replaced the shorted SOT23 diode with a MMBT3906 (PDF attached). No joy! I measured 330V across the Big cap. But NO voltage output to the other card (Logic or inverter). I will TRY to flip over & measure voltages on the NCP1200D & L6565D (PDFs attached). If anybody could point out which particular pins on them i should be focusing on, that would be great!.

                                Originally posted by Tyan View Post
                                yep, same here. And the "big" Cap next to it (C620) is also toast.
                                Tyan, may i know how do you tell it is toast? Visually, I can't see anything wrong with it. But i do not have a capacitance measurement to measure it though.
                                Attached Files

                                Comment


                                  Re: Dell 2407WFPb Monitor - Bad Cap

                                  I have not been following this thread, so I don't know if this will pertain to yours of not.
                                  I am working on this model at the moment. One thing I have noticed is the monitor will not work unless the USB card is hooked up.
                                  Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                  Comment


                                    Re: Dell 2407WFPb Monitor - Bad Cap

                                    Originally posted by newbie1 View Post
                                    Thanks PlainBill!. Splendid website!!.. I wish i could say the same for my current repair though.

                                    Update. Replaced the shorted SOT23 diode with a MMBT3906 (PDF attached). No joy! I measured 330V across the Big cap. But NO voltage output to the other card (Logic or inverter). I will TRY to flip over & measure voltages on the NCP1200D & L6565D (PDFs attached). If anybody could point out which particular pins on them i should be focusing on, that would be great!.



                                    Tyan, may i know how do you tell it is toast? Visually, I can't see anything wrong with it. But i do not have a capacitance measurement to measure it though.
                                    On the power supply, I suggest you try to see if you can measure the 5V standby voltage on the wiring harness with all the black wires. Unfortunately, there are no voltage labels on this board. If you measure the 5V, try measuring the Vcc voltages for the L6565 and NCP1200 controller chips.

                                    Comment


                                      Re: Dell 2407WFPb Monitor - Bad Cap

                                      Originally posted by newbie1 View Post
                                      Tyan, may i know how do you tell it is toast? Visually, I can't see anything wrong with it. But i do not have a capacitance measurement to measure it though.
                                      ummm, it has nearly 0 resistance. But meanwhile i´ve read endors post and had to learn that this doesn´t have to mean it´s dead. It also can be, that there´s a short between the connected parts... so i have to admit: my statement may be wrong.

                                      Comment


                                        Re: Dell 2407WFPb Monitor - Bad Cap

                                        Originally posted by jetadm123 View Post
                                        On the power supply, I suggest you try to see if you can measure the 5V standby voltage on the wiring harness with all the black wires. Unfortunately, there are no voltage labels on this board. If you measure the 5V, try measuring the Vcc voltages for the L6565 and NCP1200 controller chips.
                                        *this is getting messy.

                                        I manage to flip the Power board over & ground it. Measured 0V on ALL the pins with respect to Gnd on CN701 & CN702. Also I managed to measure the pins on the L6565 & NCP1200 with respect to the -ve pin of the Big Cap.

                                        L6565
                                        Pin 1 (INV) - 2.10V
                                        Pin 2 (COMP) - 0.12V
                                        Pin 3 (VFF) - 2.43V
                                        Pin 4 (CS) - 0v
                                        Pin 5 (ZCD) - 0v
                                        Pin 6 (GND) - NA
                                        Pin 7 (GD) - 0.1V
                                        Pin 8 (VCC) - 1.15V

                                        NCP1200
                                        Pin 1 (ADJ) - 0.39V
                                        Pin 2 (FB) - 4.5-4.7V (UNSTABLE)
                                        Pin 3 (CS) - 0.76V
                                        Pin 4 (GND) - NA
                                        Pin 5 (DRV) - 0-0.5V (UNSTABLE)
                                        Pin 6 (VCC) - 6.97-9.35 V (UNSTABLE)
                                        Pin 7 (NC) - NA
                                        Pin 8 (HV) - did not dare to measure because Max volt=500V! hee..

                                        So, I proceeded to check SOME other points on the power board from the Big cap (measured 326V) onwards down to the ICs, to find out why the VCC is low for both ICs. Then something STUPID & BAD happened.

                                        I measured 326V on Pin 2 (DRAIN) of Q651 with respect to Gnd. But got 0V on both the Pin 1 (Gate) & Pin 3 (SOURCE). The I move the probes to measure voltage between Pin 1 (Gate) & Pin 3 (SOURCE), which is VGS. A SPARK, small FIRE & MAGIC SMOKE coming from Pin 8 (HV) of NCP1200!. Also MAGIC SMOKE coming from the other side near T601!!. I quickly unplugged the main Power. When I flipped the board over R603, linking to Pin 8 (HV) of NCP1200 is visibly burnt. So, again, I need the help from you guys.

                                        1) Could someone, with the same board, identify R603 so i could replace it? I think NCP1200 will be needed to be replaced as well, right? Sigh!
                                        2) Did measuring VGS of Q651 a WISE thing to do? Will it caused the SMOKE, FIRE & BURNT? or is there something else which i missed out?

                                        what a way to start your Sunday..
                                        Attached Files

                                        Comment


                                          Re: Dell 2407WFPb Monitor - Bad Cap

                                          thats mine, reading
                                          brown black orange yellow



                                          should be 10k ohm, mine has 9,85k

                                          Comment

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