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    #1

    Dell 1800fp

    Hey guys, i'm in need of your assistance again. My old dependable 1800fp quit on me after 6+ years of 24/7 service. I turned the power on and nothing.

    The LED was dim and flashing but got brighter after a couple of minutes. The power button has no effect. I can here a faint clicking from the psu or under it.
    I read some of the other threads and did some checks listed in them and here is my findings.

    1. Visually everything looks good but dirty.
    2. No resistance between 6-7 pin on psu ICE chip. I have checked while powered on. will have to find that thread again.
    3. Pin out voltages on psu are 0v ,0v ,5.12v ,5.12v ,0v ,0v ,11.58v ,11.56v. The 5 and 12 volt fluctuate about .05v. Is the 12v to low?
    4. I did notice a couple dry joints on the transformer so sucked and resoldered those.

    Any other ideas?
    Attached Files
    Last edited by junktv; 02-09-2012, 03:56 PM.
    Tags: None
    #2
    Re: Dell 1800fp

    Originally posted by junktv View Post

    2. No resistance between 6-7 pin on psu ICE chip. I have checked while powered on. will have to find that thread again.
    3. Pin out voltages on psu are 0v ,0v ,5.12v ,5.12v ,0v ,0v ,11.58v ,11.56v. The 5 and 12 volt fluctuate about .05v. Is the 12v to low?

    Any other ideas?
    Not sure if I understood what you did in step 2. Always check resistance with power OFF. If you did check resistance across pins 6-7 with power off and you got zero ohms, then that indicates vcc is shorted to ground. If that's the case, then all voltages in step 3 should be zero.

    Also, resolder the pins for the two duo-diodes mounted on the heatsink.

    Comment

      #3
      Re: Dell 1800fp

      Here is now my almost daily response on how to measure a voltage regulator thread. I will write it generically so I can bookmark it.

      1) Circled in red are voltage regulators. Measure all 3 pins (ignore the fat tab). List the part number for each regulator. If the middle pin is "cut", you can still measure it and report the reading.

      2) Report it like this ...

      U1
      AL1117-33
      pin 1 = 0.0V DC
      pin 2 = 3.29V DC
      pin 3 = 5.01V DC

      3) The suffix in the part number, if present, tells you the output voltage. In the above example, -33 means the expected output voltage should be 3.3V +/- 1%.
      Attached Files
      Last edited by retiredcaps; 02-09-2012, 05:17 PM.
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      Comment

        #4
        Re: Dell 1800fp

        Originally posted by junktv View Post
        Is the 12v to low?
        Most of these lcd power supplies are unregulated. When working with a load (that is, the backlights on), the voltage is probably closer to 12V DC.
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        Comment

          #5
          Re: Dell 1800fp

          Originally posted by jetadm123 View Post
          Not sure if I understood what you did in step 2. Always check resistance with power OFF. If you did check resistance across pins 6-7 with power off and you got zero ohms, then that indicates vcc is shorted to ground. If that's the case, then all voltages in step 3 should be zero.

          Also, resolder the pins for the two duo-diodes mounted on the heatsink.
          Sorry i don't know all the term. The 6-7 pin was open and tested with the power off. I meant to say haven't checked powered yet in the original post.
          I hit those also just forgot about it. Had that problem on a 15" dell that caused a fuse to blow.
          Last edited by junktv; 02-09-2012, 05:29 PM.

          Comment

            #6
            Re: Dell 1800fp

            Where is picture of the inverter board?
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            Comment

              #7
              Re: Dell 1800fp

              Originally posted by retiredcaps View Post
              Where is picture of the inverter board?
              Haven't taken it apart that far yet.

              Comment

                #8
                Re: Dell 1800fp

                Originally posted by retiredcaps View Post
                Here is now my almost daily response on how to measure a voltage regulator thread. I will write it generically so I can bookmark it.

                1) Circled in red are voltage regulators. Measure all 3 pins (ignore the fat tab). List the part number for each regulator. If the middle pin is "cut", you can still measure it and report the reading.

                2) Report it like this ...

                U1
                AL1117-33
                pin 1 = 0.0V DC
                pin 2 = 3.29V DC
                pin 3 = 5.01V DC

                3) The suffix in the part number, if present, tells you the output voltage. In the above example, -33 means the expected output voltage should be 3.3V +/- 1%.
                None of these are labeled like that so I just labeled a pic with the placement ,part number and voltages i got. I hope easy to make out.
                I'm using a cheap DMT7 digital meter. I may be able to borrow a fluke or craftsman this weekend.
                Attached Files

                Comment

                  #9
                  Re: Dell 1800fp

                  When you write 3.81 - 5.04V, does this mean the DC voltage is fluctuating (i.e. not stable) between these two values?
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                    #10
                    Re: Dell 1800fp

                    Originally posted by retiredcaps View Post
                    When you write 3.81 - 5.04V, does this mean the DC voltage is fluctuating (i.e. not stable) between these two values?
                    That is correct. It was constantly bouncing around.

                    Comment

                      #11
                      Re: Dell 1800fp

                      1) Is the 5V stable at the connector on this logic board or is it fluctuating as well?

                      2) If you measure a fresh AA battery, does the multimeter display a stable reading?
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                      Comment

                        #12
                        Re: Dell 1800fp

                        If you mean coming into the board from the power supply then the 5v would fluctuate about .05v.

                        It is stable on a battery.

                        I think in another thread that fluctuation could be caused by a bad cap. These look good And are both 25v 470u but one is a sam young and other is a samwha. If that could cause it i need to see if i can find info on them. I have some 25v 470 rubycon zl but i'm not sure they have the same ohm specs.
                        Last edited by junktv; 02-09-2012, 07:38 PM.

                        Comment

                          #13
                          Re: Dell 1800fp

                          On the power board, what is the part number for IC901.
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                          Comment

                            #14
                            Re: Dell 1800fp

                            Originally posted by retiredcaps View Post
                            on the power board, what is the part number for ic901.
                            ice 2as01
                            0319lp
                            vc311999k05


                            Want to say thanks for taking the time to help.

                            Comment

                              #15
                              Re: Dell 1800fp

                              From what I can see, it looks like the power supply is outputting the required 5V and 12V. Even with the .05V fluctuation, I don't think that's enough to prevent your monitor from turning on. Moving on, it appears the problem is on the logic board. Looking at post #12 in the thread below could be the cause of your problem.

                              https://www.badcaps.net/forum/showth...ghlight=1800fp


                              If those two caps don't solve your problem, this logic board is also known to get a corrupted eeprom (the chip with the red marking on your photo). If this is chip bad, then you'll have to replace the entire logic board.
                              Last edited by jetadm123; 02-09-2012, 09:57 PM.

                              Comment

                                #16
                                Re: Dell 1800fp

                                Originally posted by jetadm123 View Post
                                From what I can see, it looks like the power supply is outputting the required 5V and 12V. Even with the .05V fluctuation, I don't think that's enough to prevent your monitor from turning on. Moving on, it appears the problem is on the logic board. Looking at post #12 in the thread below could be the cause of your problem.

                                https://www.badcaps.net/forum/showth...ghlight=1800fp


                                If those two caps don't solve your problem, this logic board is also known to get a corrupted eeprom (the chip with the red marking on your photo). If this is chip bad, then you'll have to replace the entire logic board.
                                On page 3 of that thread someone mentioned good voltage but low amps from the power supply. I figured i'd try that first so i made a harness to test with a computer psu and it worked.

                                So my problem is definitely in the power supply after all. :relief:

                                Comment

                                  #17
                                  Re: Dell 1800fp

                                  Originally posted by junktv View Post
                                  ice 2as01
                                  1) Datasheet at



                                  2) What is the DC voltage on pin 6 (VCC)? Pin 7 is your GND. Is this voltage stable or fluctuating?

                                  3) There are 2 small caps by this SMPS IC. One is C907 and I can't make out the other one. One of these is probably your startup cap. It may be 47uF 50V.

                                  Measure the DC voltage across the legs of both these caps. Are the voltages stable?
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                                    #18
                                    Re: Dell 1800fp

                                    Originally posted by retiredcaps View Post
                                    1) Datasheet at



                                    2) What is the DC voltage on pin 6 (VCC)? Pin 7 is your GND. Is this voltage stable or fluctuating?

                                    3) There are 2 small caps by this SMPS IC. One is C907 and I can't make out the other one. One of these is probably your startup cap. It may be 47uF 50V.

                                    Measure the DC voltage across the legs of both these caps. Are the voltages stable?
                                    Do i just put the neg probe on a chassis screw and positive on the 6 pin to test or should i use the 7 for ground?

                                    The cap directly beside the ic chip C907 is a sam young kmg 50v 47uf and the other C924 looks like a samwha RG 25v 33uf.

                                    Comment

                                      #19
                                      Re: Dell 1800fp

                                      Originally posted by junktv View Post
                                      Do i just put the neg probe on a chassis screw and positive on the 6 pin to test or should i use the 7 for ground?
                                      Pin 7 for GND because you are on the hot side of the board. Be careful and don't let the probes slip otherwise you could short out something.

                                      The cap directly beside the ic chip C907 is a sam young kmg 50v 47uf and the other C924 looks like a samwha RG 25v 33uf.
                                      Either one could be the startup, but my guess would be the 47uF 50V. Measure both.
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                                      Comment

                                        #20
                                        Re: Dell 1800fp

                                        Originally posted by retiredcaps View Post
                                        Pin 7 for GND because you are on the hot side of the board. Be careful and don't let the probes slip otherwise you could short out something.



                                        Either one could be the startup, but my guess would be the 47uF 50V. Measure both.
                                        I don't have a tester for caps. Unless you mean voltage at + side. If so do i go pin to pin? Sorry i forget this stuff and just want to make sure.

                                        Comment

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