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    #41
    Re: Dell 1707FPt No Power

    I've done back over this thing, without boards connected, power out pins 1 thru 4 bounce between 5.1v & 5.3v, pin 9 between .5v & 1.7v. Connect boards, pin 1 thru 4 5.24v steady, pin 9 = zero volts, and the power LED no longers comes on, I don't know what changed.

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      #42
      Re: Dell 1707FPt No Power

      Update, since the only thing I've done so far that made any difference was reflow joints on the AC inlet end of the board, I went back and reflowed & re soldered all joints. Connect AC power, steady voltage on output pins. Connect logic board and ribbon going to power button. Plug in AC, my green LED light, on (before I pushed it). Been there before. All voltages at connection pins steady and correct (as far as I know). Press power button, green LED light, off. Press it again, on. I cycle it several times, and it works good. Plug in spare ccfls, turn it on, no back light. Now, power button won't turn off. Unplug AC & replug, power button does nothing, dead again. Disconnect boards, output voltage now bounces between 5.1v & 5.3v, and when it does that, the power button does nothing when connected. What the hell is going on?

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        #43
        Re: Dell 1707FPt No Power

        I may have missed it but have you tested the inverter transformers.
        Cant see how they would affect the voltage problems you have but may as well test them as if they are gone they may not be replaceable
        POWER OFF Meter on ohms 2000 measure s1 to s2 and s3 to s4 on the attached pic.
        Attached Files
        Please upload pictures using attachment function when ask for help on the repair
        http://www.badcaps.net/forum/showthread.php?t=39740

        Comment


          #44
          Re: Dell 1707FPt No Power

          Originally posted by selldoor View Post
          I may have missed it but have you tested the inverter transformers.
          Cant see how they would affect the voltage problems you have but may as well test them as if they are gone they may not be replaceable
          POWER OFF Meter on ohms 2000 measure s1 to s2 and s3 to s4 on the attached pic.
          S1 to S2 = 443ohm S3 to S4 = 442ohm

          Comment


            #45
            Re: Dell 1707FPt No Power

            Ok the secondary windings on the inverter transformers are good.
            Can you connect the ccfls that you know work and disconnect the main board.

            With mains power to the powersupply Can you get a 3v battery or 2x1.5v in series and connect negative to ground and positive to bl on.

            Probably nothing will happen - is there a pson pin? if so try putting the 3v+
            to that instead of the Blon.
            Please upload pictures using attachment function when ask for help on the repair
            http://www.badcaps.net/forum/showthread.php?t=39740

            Comment


              #46
              Re: Dell 1707FPt No Power

              Originally posted by selldoor View Post
              Ok the secondary windings on the inverter transformers are good.
              Can you connect the ccfls that you know work and disconnect the main board.

              With mains power to the powersupply Can you get a 3v battery or 2x1.5v in series and connect negative to ground and positive to bl on.

              Probably nothing will happen - is there a pson pin? if so try putting the 3v+
              to that instead of the Blon.
              Dell saw fit not mark any pins on this board, but when I do get it to working, pin 9 had 1.73vdc, pin 10 & 11 = 0. When I connect the boards, pin 9 = 0, pin 10 = 0, pin 11 = 3.24 vdc. Press power button, pin 9 = 3.24vdc, pin 10 = 3.24vdc, pin 11 = 2.56. I don't which is power on. I've also noticed, in the wiring harness from ps/inv board to logic board, pin 10 and pin 11 are crossed. I can rigg the 3v if I knew correct pins.

              Comment


                #47
                Re: Dell 1707FPt No Power

                This is the way I'm numbering the pins. You'll have to blow the picture up a little to see my text.
                Attached Files

                Comment


                  #48
                  Re: Dell 1707FPt No Power

                  Well as pins 9 10 and 11 receive around 3v then just try it on each of them
                  (one at a time) without the main board connected but with the lamps connected.
                  Please upload pictures using attachment function when ask for help on the repair
                  http://www.badcaps.net/forum/showthread.php?t=39740

                  Comment


                    #49
                    Re: Dell 1707FPt No Power

                    Originally posted by selldoor View Post
                    Well as pins 9 10 and 11 receive around 3v then just try it on each of them
                    (one at a time) without the main board connected but with the lamps connected.
                    And use either pin 5, 6, 7, or 8 as my ground?

                    Comment


                      #50
                      Re: Dell 1707FPt No Power

                      Originally posted by maybenever View Post
                      And use either pin 5, 6, 7, or 8 as my ground?
                      Only if you have checked that they are ground pins - otherwise use a
                      groundscrew tag.
                      Please upload pictures using attachment function when ask for help on the repair
                      http://www.badcaps.net/forum/showthread.php?t=39740

                      Comment


                        #51
                        Re: Dell 1707FPt No Power

                        Originally posted by selldoor View Post
                        Only if you have checked that they are ground pins - otherwise use a
                        groundscrew tag.
                        Checking those pins back to board ground, .05 ohm, should be good to go. I'll get back.

                        Comment


                          #52
                          Re: Dell 1707FPt No Power

                          The test of applying 3v to BL_on pins, is used regularly by lots of members HOWEVER this does not work 100% of the time !!!sometimes you need to apply voltage to the Dim pin at the same time.some DAC boards MUST have the Logic board connected, similarly one of the Samsung Monitors is also the same.Normally Dell do not give you problems like that, but you should be aware.

                          Comment


                            #53
                            Re: Dell 1707FPt No Power

                            RTECH is corrct about applying the voltage to the diming pin, only if it used analog diming control (0~5v), if it uses PWM, then you will need to feed it wirh 150~200 Hz square wave generator (this will give 50% pulse width), otherwise it may not light up on some board.
                            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


                              #54
                              Re: Dell 1707FPt No Power

                              Originally posted by selldoor View Post
                              Well as pins 9 10 and 11 receive around 3v then just try it on each of them
                              (one at a time) without the main board connected but with the lamps connected.
                              Connected 2 AA batteries (3.12v) with a pushbutton switch. Apply voltage to pin 9, nothing happened, voltage to pin 10, nothing happened, voltage to pin 11, the ccfls try to light. I get a flash of light, about 3" of it at the ends where the wires are connected. Both sets flicker 3 times and stop. It's the same with just one set connected, either side, 3 flickers and stop.

                              Comment


                                #55
                                Re: Dell 1707FPt No Power

                                Originally posted by budm View Post
                                Is your meter True R.M.S? If it is, put it in AC mode and measure AC ripple voltage on the two legs of that large cap.
                                My meter now is True RMS. Got a Fluke 113 for my birthday. The AC DC is automatic fuction. Checking across the legs of the large cap, I get 166vdc, then slowly climbs up to 170.3vdc to 170.4vdc. Another strange thing, when I check for voltage on pin 9 with my $20 DMM, I get 1.73vdc (the logic board not connected). When checking with my Fluke, I get 0.00v voltage. What's up with that?

                                Comment


                                  #56
                                  Re: Dell 1707FPt No Power

                                  Originally posted by maybenever View Post
                                  Got a Fluke 113 for my birthday. The AC DC is automatic fuction.
                                  The Fluke113 is a specialized multimeter. Namely it has Vchek which tries to automagically determine the reading without the operator having to choose the correct function.

                                  As such, the default is to turn try and detect AC, DC, continuity or diode functionality automagcially. One of the limitations of the 113 is that you cannot set it to measure AC manually.

                                  Another strange thing, when I check for voltage on pin 9 with my $20 DMM, I get 1.73vdc (the logic board not connected). When checking with my Fluke, I get 0.00v voltage.
                                  The Vchek feature might be "fooled" when voltage is low (that is, it might be doing a diode test which explains the 0.000V DC reading). You can put the Fluke 113 into "manual" DCV mode by pressing the range key twice. It should show 0.000V DC. Now take your reading and it should be 1.73V DC.

                                  AFAIK, there is no way to disable Vchek on the 113. I have an older Fluke 12 which was the predecessor, but I can enable/disable the Vchek feature on it.

                                  PS. I don't recommend the Fluke 114 for electronics use because it has no diode test functionality. The 115 and 117 are good for electronics if you don't need to measure milli or micro amps.
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                                    #57
                                    Re: Dell 1707FPt No Power

                                    retiredcaps: The Vchek feature might be "fooled" when voltage is low (that is, it might be doing a diode test which explains the 0.000V DC reading). You can put the Fluke 113 into "manual" DCV mode by pressing the range key twice. It should show 0.000V DC. Now take your reading and it should be 1.73V DC.
                                    Thanks for the meter lesson, but when I set it to manual mode, I still don't voltage on that pin. The meter is working OK, I can check 1.5v battery, get 1.56vdc, I've got a 3v battery that's about shot, checks 1.43vdc., so I guess it's working, but there is no voltage detected at pin 9. Another thing, when power is first applied to the board, the 5.24 output voltage is steady, after a few minutes, it flopps between 5.1v and 5.3v. Using the min/max setting on my meter, between 5.3vdc max and -4.1vdc min. When the voltage is steady, I don't get a neg voltage at min. Am I doing this right?

                                    Comment


                                      #58
                                      Re: Dell 1707FPt No Power

                                      Originally posted by maybenever View Post
                                      When the voltage is steady, I don't get a neg voltage at min. Am I doing this right?
                                      I have a Fluke 113. Let me do some tests over the next few days. You wouldn't be the first person to report strange readings with it.
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                                      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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                                        #59
                                        Re: Dell 1707FPt No Power

                                        retiredcaps, it seems I reported these voltages in error. Testing again, in min/max mode, I record a neg voltage when ever the output voltage is stable or not. Don't know where to go from here.

                                        Comment


                                          #60
                                          Re: Dell 1707FPt No Power

                                          Okay, I did some testing with my Fluke 113 and 12.

                                          As I expected in some circuits, the Fluke 113 and 12 when used in Vchek mode will not properly report some measurements because it is working 100% as designed.

                                          The Fluke 113 is in low impedance mode all the time (optional for Fluke 12). As such it can affect the circuit under measurement. To see why, have a read through

                                          http://www.talkingelectronics.com/pr...onents.html#12

                                          The Fluke 113 has a 3k ohm input impedance. Most digital multimeters have a 10M ohm input impedance. The Fluke 12 has a 2k ohm input impedance in Vchek mode and 10M ohm for DCV "manual" mode.

                                          In my tests, the Fluke 113 and 12 (when using Vchek) will both fail to measure DCV properly in some circuits (i.e. it shows 0.0V DC). When I switch the Fluke 12 to "manual" DCV mode (with input impedance of 10M ohm), it measures the DCV properly.

                                          So if you plan to do more electronics work, you may ask the gifter to give you the receipt for the 113 and exchange it for something else like a Fluke 115 (albeit more money).
                                          Last edited by retiredcaps; 02-17-2013, 11:48 PM.
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