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Dell 1707FPt No Power

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    #1

    Dell 1707FPt No Power

    I got this monitor apart and I don't see any for sure bad caps. I've read all the threads on this monitor, but no one ever listed the pin voltage going to the logic board. When I first put AC power to the main boad, I get 2.45vdc at the two top pins, then the voltage starts falling, finally going to .o1 volts.
    I have 163vdc across the large filter cap. Am I kooking at a cap problem somewhere?
    Attached Files
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    #2
    Re: Dell 1707FPt No Power

    Originally posted by maybenever View Post
    When I first put AC power to the main boad, I get 2.45vdc at the two top pins, then the voltage starts falling, finally going to .o1 volts.
    Disconnect all boards from the power board. After doing so, are all the DC voltages on the pins stable and steady? List them like so

    pin 1 = 0.0
    pin 2 = 2.45
    etc

    If they are steady, then reconnect the main board and re-measure the same pins. Report your findings.
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      #3
      Re: Dell 1707FPt No Power

      Originally posted by retiredcaps View Post
      Disconnect all boards from the power board. After doing so, are all the DC voltages on the pins stable and steady? List them like so

      pin 1 = 0.0
      pin 2 = 2.45
      etc

      If they are steady, then reconnect the main board and re-measure the same pins. Report your findings.
      Board was disconnected when I was checking voltage. Pin 1 pin 2, same reading 2.45v and steady drop to almost nothing.

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        #4
        Re: Dell 1707FPt No Power

        What about the other pin voltages?
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          #5
          Re: Dell 1707FPt No Power

          With board turned over, pins in the upper right corner, top pin (1) and pin 2 had voltage. Don't have the board at hand to recheck, but I think pin 3 also had voltage. pin 4 & 5 were gnd, and the rest of the pins had no voltage. I checked voltage at different spots, and where I found voltage, it was counting down like the pin voltage. I did find at one spot that had 21.5v, and it seemed to be steady.

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            #6
            Re: Dell 1707FPt No Power

            Originally posted by retiredcaps View Post
            What about the other pin voltages?
            Pin 1,2,3,&4 2.45vdc and droping, pin 5,6,7,8 = no voltage. pin 9 = .8vdc, pin 10 & 11, no voltage.
            That was yesterday when I had heat in my shop, 65 degrees.
            This moring, I wanted to check the voltage to be sure, no heat, it was 35 degrees, voltage changed.
            pin 1 thru 4 = 5.3 to 5.1, but not droping.
            pin 5 thru 8 = no voltage
            pin 9 = 1.5 to .5vdc
            pin 10 & 11 = no voltage.
            In one thread, you found pin 10 to be BL and pin 11 to be brightness adjustment ( I think ).

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              #7
              Re: Dell 1707FPt No Power

              Update, went back in my shop this afternoon, 50 degree, pin 1 thru 4, 5.25vdc and holding. Pin 9, 1.73v and holding. Whats going on? Fired up the heater, held the board in front of it for a minute, voltage started droping, .01v per sec, all the the way to zero. Pin 9 seemed to stop at .03v. Pins 5 thru 8 check to be grounds, .05ohm between them and ground. This is a cap problem, right? Which ones first? (or all).
              Does anybody know what the voltage should be at these pins?

              Comment

                #8
                Re: Dell 1707FPt No Power

                Does this picture help any? I've got most of those caps on hand (panny FM), I've got them all in the correct uf, but Dell used larger volt caps than most, I'd have to get some of those.
                Attached Files

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                  #9
                  Re: Dell 1707FPt No Power

                  I suspect someone has worked on this board before. I don't recall seeing United Chemi-con KY caps on a power board mixed in with Rubycon YXG. Both brand and series are good quality.

                  The fact that it fails when heated could be a cap problem or a bad solder joint.

                  If it was my monitor, I would reflow each capacitor joint with some fresh 60/40 solder and retest.
                  Last edited by retiredcaps; 02-05-2013, 02:44 PM. Reason: grammar
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                    #10
                    Re: Dell 1707FPt No Power

                    I'm going to work on it right now, I'll get back. I wish I knew to proper output voltage, seems like one pin should be 12 or 14 volts. No markings on either board (thanks dell).

                    Comment

                      #11
                      Re: Dell 1707FPt No Power

                      Who makes these two caps? What brand and series?
                      Attached Files
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                        #12
                        Re: Dell 1707FPt No Power

                        It looks like SU Scon 0627 (M) 220uf 35v

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                          #13
                          Re: Dell 1707FPt No Power

                          Originally posted by maybenever View Post
                          It looks like SU Scon 0627 (M) 220uf 35v
                          I would replace those two for sure with Panasonic FR/FM/FC.
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                            #14
                            Re: Dell 1707FPt No Power

                            Originally posted by retiredcaps View Post
                            I would replace those two for sure with Panasonic FR/FM/FC.
                            Thanks alot for the help. I've got those in 220uf 50v FMs, I'll give it a try.
                            I'm going over the back of this board with a 10x glass, if someone has worked on it, damm, they're good.

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                              #15
                              Re: Dell 1707FPt No Power

                              Originally posted by maybenever View Post
                              I'm going over the back of this board with a 10x glass, if someone has worked on it, damm, they're good.
                              I could be wrong on that. It is just surprising to see 3 different capacitor brands used. If they were all one brand, then I wouldn't suspect anything.
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                                #16
                                Re: Dell 1707FPt No Power

                                I replaced the 220uf caps (circled in red), no change, voltage flopping between 5.14v & 5.25v, held board in front of heater a few seconds (a 35,000 btu space heater), voltage started dropping. I replaced the 10uf 50v cap (circled in yellow), voltage held steady at 5.25v on all 4 top pins. Pin 9 steady at 1.68v. After a few minutes (all voltages holding steady), I held it in front of heater, damm, the voltage did not drop, only flopped between 5.14v and 5.25v again. Unplugged AC, had a beer, plugged it back in, voltage steady again. Gotta be going in the right dirrection.The cap circled in green is a 4.7uf 50v, that one I don't have. Tomorrow, I'm connecting boards together and see if it has any life. I'll get back.
                                Attached Files

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                                  #17
                                  Re: Dell 1707FPt No Power

                                  The yellow one is the startup cap. That would have been one I would have suggested next to replace after a 60/40 reflow.

                                  The Su'scon had to go though.
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                                    #18
                                    Re: Dell 1707FPt No Power

                                    Originally posted by retiredcaps View Post
                                    The yellow one is the startup cap. That would have been one I would have suggested next to replace after a 60/40 reflow.

                                    The Su'scon had to go though.
                                    That 4.7uf cap is a Su'scon, is it a startup cap?

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                                      #19
                                      Re: Dell 1707FPt No Power

                                      Originally posted by maybenever View Post
                                      That 4.7uf cap is a Su'scon, is it a startup cap?
                                      The green cap is on the other side of the optoisolator. It may be part of the feedback circuit?
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                                        #20
                                        Re: Dell 1707FPt No Power

                                        What brand was the 10uf 50v cap (yellow)?
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