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Help to repair Viewsonic vx2255wmb monitor

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    Help to repair Viewsonic vx2255wmb monitor

    Hello everyone..
    My name is Ashwin, and i am from india.. I have been using my lcd for 3-4 years.. and it suddenly died on me.. (I think the backlight, as I can see the image if i put a flashlight on the screen).. I removed the power board and replace all the barrel-shaped capacitors.. 4 were bulged..
    Now, it still does not work.. The image is still seen, very dimmly, but otherwise, it does not work.. The power board is dac-19m011.. Kindly help me out.. I will post pics as soon as I can.. Thank u everyone,
    Regards,
    AShwin

    #2
    Re: Help to repair Viewsonic vx2255wmb monitor

    Hi.. I m uploading the pics.. Sorry for the quality..
    Attached Files

    Comment


      #3
      Re: Help to repair Viewsonic vx2255wmb monitor

      Questions: what brand/series of caps did you use to replace? I count 9 caps, did you replace all of them or just some? Is there a fuse for the inverter (probably a surface mount on the backside), and have you checked it (continuity check, open reading = bad)? It will have a reference designator beginning with F (Fxxx).

      Comment


        #4
        Re: Help to repair Viewsonic vx2255wmb monitor

        The quality of those pictures is really bad; that makes it difficult to help you. Top, at about 11 o'clock on the last picture is an SMD device, F101 that is probably the fuse for the inverter. Check continuity on it.

        At the right side of the same picture at about 3:00 o'clock are a pair of SMD transistors. They are the drivers for the inverter. Are they shorted.

        Wrog is right, what capacitors did you use as replacements?

        PlainBill
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

        Comment


          #5
          Re: Help to repair Viewsonic vx2255wmb monitor

          Hello,
          Thank you for replying..
          @Wrog: please bear with a noob.. I could not get the panasonic ones, so I used another brand available here.. Its called TEAPO.. The ratings were the exact same as the blown ones.. Yes, I replaced all the caps, except the blue ceramic ones, which I dont get here.. But, all the other cylindrical caps are replaced with high temp caps of same ratings..I replaced only 8 which I could see.. I thought the fuse was the thing next to the mains connector.. Oops.. I have not checked that.. Seems hard to desolder and resolder.. is it??

          @PlainBill: I will check continuity on the fuse now.. And how do I check if the smd transistors are shorted? Same as checking continuity? I mean open = bad?
          Would it be better to replace them both? Also any idea about their values?? THank you both for your replies..

          PS.. lol @ wrog is right.

          Comment


            #6
            Re: Help to repair Viewsonic vx2255wmb monitor

            Originally posted by cmashwin View Post
            @Wrog: please bear with a noob.. I could not get the panasonic ones, so I used another brand available here.. Its called TEAPO.. The ratings were the exact same as the blown ones.. Yes, I replaced all the caps, except the blue ceramic ones, which I dont get here.. But, all the other cylindrical caps are replaced with high temp caps of same ratings..I replaced only 8 which I could see.. I thought the fuse was the thing next to the mains connector.. Oops.. I have not checked that.. Seems hard to desolder and resolder.. is it??
            Note that Teapo is on the Bad Capacitors List (over in the FAQ subforum), but if you matched them up properly in terms of ESR and ripple capability it would not prevent it from working (it just won't work for that long). If you did not match them up properly, that's a different story. If possible, please list the series of the Teapo caps you've used (this is usually a 2 or 3 letter marking on the cap) and someone can check the datasheet(s).

            The ceramic caps don't need to be replaced unless they are visibly damaged. The 9th cap is probably the huge one laying on it's side next to the mains. This also doesn't need to be replaced unless it is visibly damaged. You are right, there is a fuse next to the mains, but there is usually another for the inverter. If the fuse next to the mains was blown, you wouldn't even get a power LED so it's probably still good. No need to desolder the fuse in order to test it.

            Originally posted by cmashwin View Post
            @PlainBill: I will check continuity on the fuse now.. And how do I check if the smd transistors are shorted? Same as checking continuity? I mean open = bad?
            Would it be better to replace them both? Also any idea about their values?? THank you both for your replies..
            You'll want to test the transistors using a resistance check between all legs (1/2, 1/3, 2/3) and report back what the values are... anything low (under 10-20 ohms or so) indicates a possible short. If this happens, you'll need to remove them from the board and test them again. If they still show a possible short, they need to be replaced. Make sure to record their markings before you removed them in case they are damaged. From time to time, it's difficult to remove these because sometimes they are glued to the pcb in addition to having their legs soldered. Post the markings here so that a suitable equivalent can be found.

            Comment


              #7
              Re: Help to repair Viewsonic vx2255wmb monitor

              Originally posted by cmashwin View Post
              Hello,
              Thank you for replying..

              @PlainBill: I will check continuity on the fuse now.. And how do I check if the smd transistors are shorted? Same as checking continuity? I mean open = bad?
              Would it be better to replace them both? Also any idea about their values?? THank you both for your replies..

              PS.. lol @ wrog is right.
              Fuse: Set DMM on 200 ohms scale. Measure resistance across fuse. Less than 1 ohms is good, > 5 ohms is open; in between short the leads of the dmm together and check your reading. It should be less than 1 ohm.

              Transistors. Set the DMM to the 200 ohms scale. As Wrog says, measure the resistance between all pins on the transistor. If all read < 10 ohms, no need to pull the transistor yet, it's bad.

              PlainBill
              For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

              Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

              Comment


                #8
                Re: Help to repair Viewsonic vx2255wmb monitor

                @wrog: Thank you for the tips.. the caps say sek 105 degree C.. I have not changed the huge one lying down.. Its looking quite new so I didnt think it was to be replaced..

                @PlainBill: Thank you.. I will grab my multimeter as soon as I am home and will post the resistance values.. By the way, a friend suggested that to check the fuse, I can "temporarily short it" with a piece of wire and check it.. IS that safe to do?? I cannot understand the value of the smd drivers.. I will write down what I can read on top of it.. Should they both be the same""
                SMD1
                9973gh
                g25191

                smd2
                9973gh
                g25151
                The smd2 surface looks a bit blurred, could it be due to damage?? The letters are not clear and the plastic itself looks duller than the smd1.. Also, should the smd values be the same??

                Comment


                  #9
                  Re: Help to repair Viewsonic vx2255wmb monitor

                  Originally posted by cmashwin View Post
                  @wrog: Thank you for the tips.. the caps say sek 105 degree C.. I have not changed the huge one lying down.. Its looking quite new so I didnt think it was to be replaced..
                  I will seek the datasheets for Teapo SEK series and try to interpret.

                  Originally posted by cmashwin View Post
                  By the way, a friend suggested that to check the fuse, I can "temporarily short it" with a piece of wire and check it.. IS that safe to do??
                  No. He probably suggested it because it'll be YOUR house that burns down if it fails! Seriously, you'll hear the seniors here talk about it quite often: fuses usually blow for a reason. Jumping over the fuse protection will cause other components to fail (at best) and possibly a fire (at worst).

                  Comment


                    #10
                    Re: Help to repair Viewsonic vx2255wmb monitor

                    Thank you Wrog.. I wont do that then... I will post the smd driver values and the fuse value soon.. Thank you for your patience and help..

                    Comment


                      #11
                      Re: Help to repair Viewsonic vx2255wmb monitor

                      Here is the Teapo electrolytic caps datasheet... SE (SEK) are general purpose caps and not low ESR (low impedence)/high ripple. If Teapo is the only brand you are able to get, it appears that the SJ series would be suitable in this application.

                      Edit: Not saying this is definitely the problem, but it could be a contributor to what you are seeing.
                      Attached Files
                      Last edited by Wrog; 10-27-2010, 01:27 PM. Reason: Clarification

                      Comment


                        #12
                        Re: Help to repair Viewsonic vx2255wmb monitor

                        Hello Wrog.. I found these caps after a week of searching here I bought the best available.. I can try to get the better ones.. But will the sek caps I got work? I mean are they really bad or will they work atleast a while??

                        Comment


                          #13
                          Re: Help to repair Viewsonic vx2255wmb monitor

                          Originally posted by cmashwin View Post
                          But will the sek caps I got work? I mean are they really bad or will they work atleast a while??
                          Check the transistors as Wrog and PlainBill suggest. If you can see the image dimly, it suggests that the one or more of your transistors are shorted.
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                          Comment


                            #14
                            Re: Help to repair Viewsonic vx2255wmb monitor

                            Originally posted by cmashwin View Post
                            Hello Wrog.. I found these caps after a week of searching here I bought the best available.. I can try to get the better ones.. But will the sek caps I got work? I mean are they really bad or will they work atleast a while??
                            Short term they will probably work, but long term it may cause problems.

                            Comment


                              #15
                              Re: Help to repair Viewsonic vx2255wmb monitor

                              hi i checked the resistances of the smd transistors.. i think the soldered top chunk is base.. im gettiing high resistance.. from 700 to max.. what does this mean?

                              Comment


                                #16
                                Re: Help to repair Viewsonic vx2255wmb monitor

                                hi i checked the resistances of the smd transistors.. i think the soldered top chunk is collector.. im gettiing high resistance.. from 700 to max when on the 2000ohm range.. what does this mean? if i need to replace the transistors, which shud i buy? im not able to find the 9973gh anywhere.. any alternatives?

                                ps.. sorry aboutt the wrong and hastily posted, previous post.

                                Comment


                                  #17
                                  Re: Help to repair Viewsonic vx2255wmb monitor

                                  Also, the thing that you guys pointed out as fuse, does not have a number starting from f.. THe thing read "pj71" and down it read 1T or it maybe IT.. IS this the fuse?? Please help.

                                  Comment


                                    #18
                                    Re: Help to repair Viewsonic vx2255wmb monitor

                                    Hey all... ITs FIXED!!! It was the burnt looking transistor.. It was a real pig to remove.. THey had soldered a huge chunk and glued the thing as well.. But, I was able to remove it and put a new one in.. Its working as good as ever now.. Thank you all for your support.. Specially Wrog and PlainBill..

                                    Comment


                                      #19
                                      Re: Help to repair Viewsonic vx2255wmb monitor

                                      Outstanding, nice work!

                                      Comment


                                        #20
                                        Re: Help to repair Viewsonic vx2255wmb monitor

                                        Originally posted by cmashwin View Post
                                        Hey all... ITs FIXED!!! It was the burnt looking transistor.. It was a real pig to remove.. THey had soldered a huge chunk and glued the thing as well.. But, I was able to remove it and put a new one in.. Its working as good as ever now.. Thank you all for your support.. Specially Wrog and PlainBill..
                                        Hi there!! I have exactly the same monitor with exactly the same problem - the backlight died after ~3 years (right after the warranty expired..). Could you tell me which transistor you had to replace and what part have you used? I would appreciate your help.. I still have to open up the monitor and see what's going on but at least so i can get mentally prepared

                                        Thank you!

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