BenQ G2420HD white screen

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  • Grundell
    Member
    • May 2013
    • 14
    • Australia

    #1

    BenQ G2420HD white screen

    Hi guys,
    This is the my first post on these forums, I have a good grasp of electrical theory. Problem is I don't to do PCB work very often and I'm quite rusty at the moment. I really would like to gain a bit more exp. troubleshooting and repairing at a component lvl. In saying that it leads me to my first issue.

    I have a G2420HD BenQ PC monitor that I use with DVI-D (single link). Today I was using my PC as per usual when all of a sudden the video image disappeared and all I was left with was a white screen. I believe this to be the back-lighting only. So I rebooted as you do, only to be met with the same blank white screen. My mate and I who consider ourselves to be quite PC-savvy started troubleshooting, ruling out the GFX card by testing my PC on his monitor with success. So I have pulled the monitor apart and have discovered 3 things of note. A mainboard, a smaller video board and the ribbon cable that connects the LCD screen to the video board.

    I have inspected the capacitors and no bulging or electrolyte leakage is evident. All solder joints look solid with minimal frosting (likely machine joints), and no blackening of any joints is evident. Does anyone have any exp. with this kind of repair. As I would like to start multimeter testing from the right point. I can take pictures of the components if necessary.

    Cheers
  • smason
    Badcaps Legend
    • Feb 2010
    • 1652
    • Canada

    #2
    Re: BenQ G2420HD white screen

    Hi, and welcome.

    White screen is usually a Tcon board problem, and often just a fuse.
    Look for a surface mount fuse on the t-con board.
    If you post some pictures, we can point it out if you're having trouble finding it.
    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

    Comment

    • Grundell
      Member
      • May 2013
      • 14
      • Australia

      #3
      Re: BenQ G2420HD white screen

      Thank you for the quick reply, I suspected the fuse but thought there would be no back-light if it was blown. There is a ceramic fuse on the large (T-con) board with soldered end caps. Is this the one you are referring to?

      Comment

      • smason
        Badcaps Legend
        • Feb 2010
        • 1652
        • Canada

        #4
        Re: BenQ G2420HD white screen

        Originally posted by Grundell
        Thank you for the quick reply, I suspected the fuse but thought there would be no back-light if it was blown. There is a ceramic fuse on the large (T-con) board with soldered end caps. Is this the one you are referring to?
        You are correct if you mean the fuse on the inverter/power board, if it was blown you'd have no backlights.

        The Tcon is the board connected to the LCD panel, not the one with the inverters/power supply, or the video logic/VGA connector.
        36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

        Comment

        • Grundell
          Member
          • May 2013
          • 14
          • Australia

          #5
          Re: BenQ G2420HD white screen

          The T-con board has no visible fuses, the following pictures are of the T-con board and the mainboard with the power supply.
          Attached Files

          Comment

          • wobbin
            Member
            • Apr 2013
            • 18
            • United Kingdom

            #6
            Re: BenQ G2420HD white screen

            That's the main board rather than the TCON.

            You'll probably find the TCON hiding under a metal screening cover on the back of the LCD panel - it'll be where that big flat ribbon cable is connecting to.

            HTH

            Comment

            • Grundell
              Member
              • May 2013
              • 14
              • Australia

              #7
              Re: BenQ G2420HD white screen

              Here are some photos of the T-con, I can't see any fuses but there is a circular battery of some description. I assume holds the settings for your monitor.
              Attached Files
              Last edited by Grundell; 05-27-2013, 11:51 AM. Reason: found the fuse, it's very small. Would testing the continuity of the fuse be ok whilst installed on the TCON?

              Comment

              • smason
                Badcaps Legend
                • Feb 2010
                • 1652
                • Canada

                #8
                Re: BenQ G2420HD white screen

                Originally posted by Grundell
                Here are some photos of the T-con, I can't see any fuses but there is a circular battery of some description. I assume holds the settings for your monitor.
                The pic is a bit hard to see, but see the red circle, does that say F1?
                Attached Files
                36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                Comment

                • Grundell
                  Member
                  • May 2013
                  • 14
                  • Australia

                  #9
                  Re: BenQ G2420HD white screen

                  It sure does, can I test it's continuity whilst installed without causing anymore damage?

                  Comment

                  • Grundell
                    Member
                    • May 2013
                    • 14
                    • Australia

                    #10
                    Re: BenQ G2420HD white screen

                    bump

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #11
                      Re: BenQ G2420HD white screen

                      Just measure the voltage of both ends of the fuse against chassis ground to see what you read.
                      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

                      • smason
                        Badcaps Legend
                        • Feb 2010
                        • 1652
                        • Canada

                        #12
                        Re: BenQ G2420HD white screen

                        Originally posted by Grundell
                        It sure does, can I test it's continuity whilst installed without causing anymore damage?
                        Yes, with the power disconnected, or what Budm said, whichever is easiest for you.
                        36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                        Comment

                        • retiredcaps
                          Badcaps Legend
                          • Apr 2010
                          • 9271

                          #13
                          Re: BenQ G2420HD white screen

                          Originally posted by Grundell
                          It sure does, can I test it's continuity whilst installed without causing anymore damage?
                          Continuity is a poor way to test a fuse. There is no industry standard wrt to what is "continuous" on multimeters. Some multimeters consider something "continuous" if the reading is less than 1800 ohms.

                          A good fuse should measure less than 1.0 ohms.
                          --- begin sig file ---

                          If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                          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.

                          Please do not post inline and offsite as they slow down the loading of pages.

                          --- end sig file ---

                          Comment

                          • Grundell
                            Member
                            • May 2013
                            • 14
                            • Australia

                            #14
                            Re: BenQ G2420HD white screen

                            Well it's good and bad haha. With the ribbon cable disconnected and no PWR F1 is definitely 'OL' (open), so the fuse is KIA. Just want to confirm that this blown fuse is responsible for the all white screen and no image. If someone could provide a brief description for my peace of mind that would be fantastic.
                            Moving fwd to repair, where can i get a part no. and specs for this specific fuse? Considering it is a "fuse for ants."

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: BenQ G2420HD white screen

                              Looking like this?
                              http://s807.photobucket.com/user/bud...ml?sort=3&o=20
                              Also read my guides under my signature.
                              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

                              • retiredcaps
                                Badcaps Legend
                                • Apr 2010
                                • 9271

                                #16
                                Re: BenQ G2420HD white screen

                                Originally posted by Grundell
                                Just want to confirm that this blown fuse is responsible for the all white screen and no image.
                                Yes a blown fuse is causing your white screen. A fuse can blow because something is shorted on the tcon board or it died from age/thermal stress.

                                Moving fwd to repair, where can i get a part no. and specs for this specific fuse? Considering it is a "fuse for ants."
                                A clear focused picture of F1 helps us help you.
                                Last edited by retiredcaps; 05-28-2013, 01:14 AM.
                                --- begin sig file ---

                                If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                                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.

                                Please do not post inline and offsite as they slow down the loading of pages.

                                --- end sig file ---

                                Comment

                                • Grundell
                                  Member
                                  • May 2013
                                  • 14
                                  • Australia

                                  #17
                                  Re: BenQ G2420HD white screen

                                  Originally posted by retiredcaps
                                  Yes a blown fuse is causing your white screen. A fuse can blow because something is shorted on the tcon board or it died from age/thermal stress.
                                  Is there any recommendations for troubleshooting to determine which cap would have shorted to blow the fuse, or is it best to replace the fuse and give it the benefit of the doubt?

                                  Comment

                                  • Grundell
                                    Member
                                    • May 2013
                                    • 14
                                    • Australia

                                    #18
                                    Re: BenQ G2420HD white screen

                                    This is the best pic I can get at this stage.
                                    Attached Files

                                    Comment

                                    • Lumberjack777
                                      Badcaps Veteran
                                      • Dec 2010
                                      • 464

                                      #19
                                      Re: BenQ G2420HD white screen

                                      Originally posted by Grundell
                                      This is the best pic I can get at this stage.
                                      With that photo all I can tell is that it's white.
                                      Can you get a magnifying glass and read some info from it?
                                      It might have a "W" or an "M" or some capital letter.

                                      Comment

                                      • Grundell
                                        Member
                                        • May 2013
                                        • 14
                                        • Australia

                                        #20
                                        Re: BenQ G2420HD white screen

                                        I don't have a magnifying glass, I can't make out a letter on the fuse. I will try to get better pictures for you. Is there any other way to work out what fuse it is from schematics etc. My main concern however is that the new fuse will blow straight away. Should I bridge the fuse to test if it works, or should I do voltage checks on the TCON before I replace the fuse?

                                        Comment

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