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    #1

    Dell 1907FPc 2 seconds to black

    Dell 1907FPc 2 seconds to black.

    I resoldered the 2 inverter transformers but it didn't help.

    The capacitors appear to be united chemicon ky series (kxg for the big one).

    Tested the fuses and they all check out ok

    Tested the Q900 mosfet and i'm not getting anything under 30ohms.

    Lastly i used a test monitor with a cracked screen but working ccfl's and i'm still getting 2 seconds to black.

    Is there anything else to check?

    Thanks
    Bill
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    #2
    Re: Dell 1907FPc 2 seconds to black

    Originally posted by Mr Bill View Post
    Is there anything else to check?
    Measure the resistance of the secondary transformers. One is circled in red and other in yellow (pins 7 and 8). Report both measurements. If they are good, they should be within 3% of each other.
    Attached Files
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      #3
      Re: Dell 1907FPc 2 seconds to black

      Originally posted by Mr Bill View Post
      Tested the Q900 mosfet and i'm not getting anything under 30ohms.
      Q900 is your power mosfet. If it wasn't working, you would not get any power.

      The 2 mosfets in the inverter section are on the backside sandwiching the inverter pwm IC (Q801). Check those for shorts.
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        #4
        Re: Dell 1907FPc 2 seconds to black

        Originally posted by retiredcaps View Post
        Q900 is your power mosfet. If it wasn't working, you would not get any power.

        The 2 mosfets in the inverter section are on the backside sandwiching the inverter pwm IC (Q801). Check those for shorts.
        The inverter transformers measure 444 Kohm on the one and 447 Kohm on the other.

        Now the inverter pwm IC (Q801-Q803)
        Q801 is being a bit funny. I'll get a reading with the red probe on say pin 1 and black on pin 2 but if i reverse the leads i'm getting 0L.

        All the others i'm getting something in either K or M ohms no matter if i reverse the probes.

        So would you suspect Q801?

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          #5
          Re: Dell 1907FPc 2 seconds to black

          The mosfets are circled in blue. The pwm IC is in yellow.

          What is the part number of Q801?
          Attached Files
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            #6
            Re: Dell 1907FPc 2 seconds to black

            Originally posted by retiredcaps View Post
            The mosfets are circled in blue. The pwm IC is in yellow.

            What is the part number of Q801?
            The part # is ZC11. The 11 is written sideways.

            Here are the readings for the mosfets circled in blue

            1-1 0L
            1-2 29.4 Kohm
            1-3 0L
            1-4 4.18 Mohm

            2-1 0L
            2-2 24.86 Mohm
            2-3 0L
            2-4 11.06 Mohm

            3-1 0L
            3-2 6.53 Mohm
            3-3 0L
            3-4 3.83 Mohm

            4-1 0L
            4-2 24.54 Kohm
            4-3 0L
            4-4 9.46 Mohm

            And the other.....

            1-1 0L
            1-2 24.17 Kohm
            1-3 0L
            1-4 12.16 Mohm

            2-1 0L
            2-2 8.85 Mohm
            2-3 0L
            2-4 6.45 Mohm

            3-1 0L
            3-2 4.91 Mohm
            3-3 0L
            3-4 23.24 Kohm

            4-1 0L
            4-2 12.87 Mohm
            4-3 0L
            4-4 9.38 Mohm

            Comment

              #7
              Re: Dell 1907FPc 2 seconds to black

              The mosfets in blue might be 8 pin (hard to tell from the photo). Look at the part number and find its datasheet.

              Here is how I measure multipin mosfets for shorts.

              From

              https://www.badcaps.net/forum/showpo...4&postcount=19

              Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

              Simply test

              a) black on pin S1- red on pin G1 - record ohms
              b) black on pin S1- red on pin D1 - record ohms
              c) black on pin G1- red on pin D1 - record ohms

              Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

              Note: a shorted mosfet would likely cause a very brief flash of the backlight or no backlight.

              Here is a case study.

              https://www.badcaps.net/forum/showthread.php?t=17659
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                #8
                Re: Dell 1907FPc 2 seconds to black

                Originally posted by Mr Bill View Post
                The part # is ZC11. The 11 is written sideways.
                Sorry, I meant IC801 (on the back). It looks like a 16 pin IC.
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                  #9
                  Re: Dell 1907FPc 2 seconds to black

                  Originally posted by Mr Bill View Post
                  Lastly i used a test monitor with a cracked screen but working ccfl's and i'm still getting 2 seconds to black.
                  Describe how you did this test so we are on the same page.
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                    #10
                    Re: Dell 1907FPc 2 seconds to black

                    Originally posted by retiredcaps View Post
                    Sorry, I meant IC801 (on the back). It looks like a 16 pin IC.
                    The IC801 numbers are:

                    0Z9938GN
                    A627R2 3G
                    0614B

                    the 2 mosfet numbers are:

                    9945N
                    AAF60

                    Here are my readings

                    S1-G1 17.37 M ohm
                    S1-D1 3.67 K ohm
                    G1-D1 0L

                    S2-G2 17.42 M ohm
                    S2-D2 1.077 K ohm
                    G2-D2 0L

                    And the other one:

                    S1-G1 17.35 M ohm
                    S1-D1 1.070 K ohm
                    G1-D1 0L

                    S2-G2 17.23 M ohm
                    S2-D2 1.061 K ohm
                    G2-D2 0L

                    Comment

                      #11
                      Re: Dell 1907FPc 2 seconds to black

                      Your mosfets are good.
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                        #12
                        Re: Dell 1907FPc 2 seconds to black

                        Originally posted by retiredcaps View Post
                        Describe how you did this test so we are on the same page.
                        I removed the back from the broken screen monitor and plugged the ccfl's from that monitor into the power supply/inverter of the dell 1907FPc monitor.

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                          #13
                          Re: Dell 1907FPc 2 seconds to black

                          Originally posted by Mr Bill View Post
                          I removed the back from the broken screen monitor and plugged the ccfl's from that monitor into the power supply/inverter of the dell 1907FPc monitor.
                          Humour me and try it as described in section #5 at

                          https://www.badcaps.net/forum/showpo...6&postcount=20

                          You don't have to remove the ccfls from the broken screen. Just stretch the connector to reach the Dell and don't let the two monitors touch (use cardboard or something).
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                            #14
                            Re: Dell 1907FPc 2 seconds to black

                            Originally posted by retiredcaps View Post
                            Humour me and try it as described in section #5 at

                            https://www.badcaps.net/forum/showpo...6&postcount=20

                            You don't have to remove the ccfls from the broken screen. Just stretch the connector to reach the Dell and don't let the two monitors touch (use cardboard or something).
                            I'm getting a hiss on the one of the bulbs. I guess i'll be disassembling the screen

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                              #15
                              Re: Dell 1907FPc 2 seconds to black

                              Originally posted by Mr Bill View Post
                              I'm getting a hiss on the one of the bulbs. I guess i'll be disassembling the screen
                              You might have a cracked ccfl.

                              Well, at least you might have spares. I was able to put a 4:3 ratio 19 inch ccfl entire assembly into a 16:9 19 inch monitor. It is obviously shorter, but it works ... until I broke a tab bond!

                              Now I get this nice black 1.5 inch stripe where the bond is unglued from the glass.
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                                #16
                                Re: Dell 1907FPc 2 seconds to black

                                It was a bad tube but now i'm getting a white stripe at the one side. Auto adjusting the monitor did help a little bit. I rechecked the connectors but i'm not seeing any pins that are bent. The lvds connector to the screen is secure. Would a tab bond cause this issue. I don't think i damaged them but anything is possible.
                                Attached Files

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                                  #17
                                  Re: Dell 1907FPc 2 seconds to black

                                  Originally posted by Mr Bill View Post
                                  Would a tab bond cause this issue. I don't think i damaged them but anything is possible.
                                  Those tab bonds are very fragile. It is possible that 2 or 3 came unwelded from the glass which would explain the stripe. If I recall correctly, my stripe was black.
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