HP L1925 LCD Video Input Logic Board won't accept signal

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  • maverick530
    Senior Member
    • Dec 2008
    • 107

    #1

    HP L1925 LCD Video Input Logic Board won't accept signal

    I have an HP L1925 LCD Video Input Logic Board that powers on, and I get the standard "check signal cable" display, but as soon as I plug in a source to either the DVI or Analog 15-Pin VGA, it immediately says "no signal" and places the monitor into standby. I've tried all different resolutions and cable types, but to no avail.

    What could be the cause of the board not accepting a signal? Could there be a blown capacitor somewhere? What else could I test?
    Attached Files
  • EGuevarae
    Badcaps Legend
    • Nov 2008
    • 1336
    • USA

    #2
    Re: HP L1925 LCD Video Input Logic Board won't accept signal

    I can only figure a TAICON from the picture. Can you give info on the other caps (cap, Voltage, brand)?
    There are 10 kind of people in this world: those that understand binary, and those who don't.
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    • PCBONEZ
      Grumpy Old Fart
      • Aug 2005
      • 10661
      • USA

      #3
      Re: HP L1925 LCD Video Input Logic Board won't accept signal

      DVI and VGA are not hot-swap.
      Turn it off when attaching cables.
      Mann-Made Global Warming.
      - We should be more concerned about the Intellectual Climate.

      -
      Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

      - Dr Seuss
      -
      You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
      -

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      • maverick530
        Senior Member
        • Dec 2008
        • 107

        #4
        Re: HP L1925 LCD Video Input Logic Board won't accept signal

        Once plugged in to inputs, I've tried cycling the power off and then on again, so that the cables are already plugged in, but as soon as this board detects a signal, it shuts down. I've never seen anything like it.

        Comment

        • maverick530
          Senior Member
          • Dec 2008
          • 107

          #5
          Re: HP L1925 LCD Video Input Logic Board won't accept signal

          The smaller caps around the DVI/VGA inputs are black TEAPO 12/02 16v 10uF SS 105 degrees C.

          Slightly larger brown ones are: TAICON 16v 100uF 0304(M) 105 deg C (VT).

          There are also some larger 470uF TAICON, and the one big green one is TAICON as well.

          Comment

          • maverick530
            Senior Member
            • Dec 2008
            • 107

            #6
            Re: HP L1925 LCD Video Input Logic Board won't accept signal

            I wonder if it's the TEAPOs that are the culprits since I have another of the same boards that is 100% TAICON caps (exhibits different problem).

            Comment

            • EGuevarae
              Badcaps Legend
              • Nov 2008
              • 1336
              • USA

              #7
              Re: HP L1925 LCD Video Input Logic Board won't accept signal

              Originally posted by maverick530
              The smaller caps around the DVI/VGA inputs are black TEAPO 12/02 16v 10uF SS 105 degrees C.

              Slightly larger brown ones are: TAICON 16v 100uF 0304(M) 105 deg C (VT).

              There are also some larger 470uF TAICON, and the one big green one is TAICON as well.

              Teapo

              Replace the 470uf ones & test. Then if not working, the 100uf and then the smaller (10uf) ones.
              I've seen suggested the use of Panasonic FC series (Digikey) more than once around here. I ordered some of them, but in the meantime I've used Rubycons that I got from dead boards and so far so good....
              There are 10 kind of people in this world: those that understand binary, and those who don't.
              • ASUS ROG Maximus IX Code
              • Intel Core i5-7600K 3.8GHz
              • 16gb GSKILL TridentZ RGB DDR4-3200
              • 1 M2 SSD + 2 WD Blue 1TB (Mirrored)
              • Windows 10 Pro x64
              • GeForce GT1050
                2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

              Comment

              • maverick530
                Senior Member
                • Dec 2008
                • 107

                #8
                Re: HP L1925 LCD Video Input Logic Board won't accept signal

                I finally got around to testing this board with a digital multimeter (DMM). On Ohm Resistence test (setting 2000), I saw that the following 4 capacitors (circled in attachments) registered shorted (0 value basically): 2 100uF and 2 10uF. *I tested them on-board*--haven't removed them yet.

                My question is, if I replace these 4, do you think it'll work? Do Caps normally go bad around each other like this? How sure can I be that it is the caps, and not some other component on the board?
                Attached Files

                Comment

                • EGuevarae
                  Badcaps Legend
                  • Nov 2008
                  • 1336
                  • USA

                  #9
                  Re: HP L1925 LCD Video Input Logic Board won't accept signal

                  Originally posted by maverick530
                  I finally got around to testing this board with a digital multimeter (DMM). On Ohm Resistence test (setting 2000), I saw that the following 4 capacitors (circled in attachments) registered shorted (0 value basically): 2 100uF and 2 10uF. *I tested them on-board*--haven't removed them yet.

                  My question is, if I replace these 4, do you think it'll work? Do Caps normally go bad around each other like this? How sure can I be that it is the caps, and not some other component on the board?
                  Have you tested the same caps on the other board?
                  There are 10 kind of people in this world: those that understand binary, and those who don't.
                  • ASUS ROG Maximus IX Code
                  • Intel Core i5-7600K 3.8GHz
                  • 16gb GSKILL TridentZ RGB DDR4-3200
                  • 1 M2 SSD + 2 WD Blue 1TB (Mirrored)
                  • Windows 10 Pro x64
                  • GeForce GT1050
                    2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

                  Comment

                  • maverick530
                    Senior Member
                    • Dec 2008
                    • 107

                    #10
                    Re: HP L1925 LCD Video Input Logic Board won't accept signal

                    Yes, I actually have 3 of these boards--all with varying problems. The other 2 check out fine on these same contacts. In other words, the others do not show a short for these caps.

                    Comment

                    • EGuevarae
                      Badcaps Legend
                      • Nov 2008
                      • 1336
                      • USA

                      #11
                      Re: HP L1925 LCD Video Input Logic Board won't accept signal

                      Change them all. Teapos / Taicons give problems. You can start changing those at the signal input area, and then if it starts working properly, go ahead and change all the others now to prevent further problems.
                      There are 10 kind of people in this world: those that understand binary, and those who don't.
                      • ASUS ROG Maximus IX Code
                      • Intel Core i5-7600K 3.8GHz
                      • 16gb GSKILL TridentZ RGB DDR4-3200
                      • 1 M2 SSD + 2 WD Blue 1TB (Mirrored)
                      • Windows 10 Pro x64
                      • GeForce GT1050
                        2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

                      Comment

                      • maverick530
                        Senior Member
                        • Dec 2008
                        • 107

                        #12
                        Re: HP L1925 LCD Video Input Logic Board won't accept signal

                        Where's the best place to buy these caps online? What brand should I get? Thanks in advance,

                        Comment

                        • EGuevarae
                          Badcaps Legend
                          • Nov 2008
                          • 1336
                          • USA

                          #13
                          Re: HP L1925 LCD Video Input Logic Board won't accept signal

                          Panasonic FC series have been suggested more than once around here.
                          Reliable caps.
                          You can get them from Digikey.com
                          There are 10 kind of people in this world: those that understand binary, and those who don't.
                          • ASUS ROG Maximus IX Code
                          • Intel Core i5-7600K 3.8GHz
                          • 16gb GSKILL TridentZ RGB DDR4-3200
                          • 1 M2 SSD + 2 WD Blue 1TB (Mirrored)
                          • Windows 10 Pro x64
                          • GeForce GT1050
                            2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

                          Comment

                          • maverick530
                            Senior Member
                            • Dec 2008
                            • 107

                            #14
                            Re: HP L1925 LCD Video Input Logic Board won't accept signal

                            Ok, I just replaced the 4 suspected "bad" caps, and each circled tap still registers as shorted. I tested the "bad" caps once out, and they all seem to hold charges. So, it turns out that it wasn't a cap problem at all, and I'm still left with a bad monitor that won't accept a signal. What else can I try?

                            Comment

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