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    #1

    Viewsonic VX724 - replaced 4 caps, still dead

    Hi all,

    Thanks for this great resource and in advance for any help with my current failing monitor. It is a VX724 and it's out of warranty by almost a year past, so after some quick research into the problem I figured caps would be it. Took it apart, and have replaced 4 capacitors as shown in this photo:


    However upon putting it back together, it's still doing the same thing - blinking green power light. Tried without the cover on, and could hear faintly the sound of what was a cap constantly trying to charge up, but that is merely a guess.

    I ripped it all apart again, checked all the soldering work, wiring, etc, still nothing. Then noticed after reading a similar post online that there is an entire area of the PCB that is discolored / darkened / burnt looking on the edge where there is a transistor, resistor, and some more caps. Any coincidence that the LCD died on a very hot day with no A/C ?

    There also appears to be another blown cap, a rectangular orange one that has H154J E 250MPP3 on it. Not sure but perhaps 15.4 pF 250V ? or 25 V ? Anyways do you guys think the entire board is fried or would replacing the components that are within the burnt section possibly do it?



    (discoloration is on the left side and covers about a vertical 1" strip)

    Anyone that has done successful VX724 repairs, please share!

    Cheers

    Pete
    Tags: None
    #2
    Re: Viewsonic VX724 - replaced 4 caps, still dead

    Originally posted by tacticalgamer
    Hi all,

    Thanks for this great resource and in advance for any help with my current failing monitor. It is a VX724 and it's out of warranty by almost a year past, so after some quick research into the problem I figured caps would be it. Took it apart, and have replaced 4 capacitors as shown in this photo:

    However upon putting it back together, it's still doing the same thing - blinking green power light. Tried without the cover on, and could hear faintly the sound of what was a cap constantly trying to charge up, but that is merely a guess.

    I ripped it all apart again, checked all the soldering work, wiring, etc, still nothing. Then noticed after reading a similar post online that there is an entire area of the PCB that is discolored / darkened / burnt looking on the edge where there is a transistor, resistor, and some more caps. Any coincidence that the LCD died on a very hot day with no A/C ?

    There also appears to be another blown cap, a rectangular orange one that has H154J E 250MPP3 on it. Not sure but perhaps 15.4 pF 250V ? or 25 V ? Anyways do you guys think the entire board is fried or would replacing the components that are within the burnt section possibly do it?


    (discoloration is on the left side and covers about a vertical 1" strip)

    Anyone that has done successful VX724 repairs, please share!

    Cheers

    Pete
    Before you go any further, follow the link in my signature on attaching pictures. I'm old and crotchety and refuse to help those who can't follow directions.

    The discoloration may be normal. The heat sink probably got quite warm.

    There is a small capacitor (probably 22uF, 50 V) near the lower right corner of the SMPS transformer. If that is bad it can cause the symptoms you describe.

    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

      #3
      Re: Viewsonic VX724 - replaced 4 caps, still dead

      After doing what PlainBill suggested, also check both CCFLs. Do this by only hooking 1 up at a time, leaving the other(s) disconnected, and seeing if the screen lights up. It won't stay up, but if it lights, you know the CCFL is likely not bad.

      Comment

        #4
        Re: Viewsonic VX724 - replaced 4 caps, still dead

        From my experience, blinking green light is not a CCFL issue.

        Do what PlainBill suggested about the other cap.

        Also, check if the Main board (green colour ones) have any domed caps.

        Comment

          #5
          Re: Viewsonic VX724 - replaced 4 caps, still dead

          What are your replacement caps? They have what look like Rubycon K stamps, but I'm not convinced...
          What's the cap next to the connector to the mainboard?

          Comment

            #6
            Re: Viewsonic VX724 - replaced 4 caps, still dead

            Hey all , thanks again for the quick feedback you all rock. Sorry about the pics not being attached, have read the rules and will remember for next time (not able to edit the post it seems).

            I did not notice the cap Plainbill mentioned to be domed but it does seem slightly bigger than others of its size. I will go back to the store and grab one of those.

            Also, the caps say 'Rubycon' on the labels. Is this a good enough brand? The cap next to the board connection is a 330uF 25V, seanc.

            Lucky- the green board seemed to be okay, but I am going to attach an image of it in this post.
            Attached Files

            Comment

              #7
              Re: Viewsonic VX724 - replaced 4 caps, still dead

              Upon further inspection the one cap mentioned that I used to replace is actually an HSC branded one. Is this an okay brand ?

              Comment

                #8
                Re: Viewsonic VX724 - replaced 4 caps, still dead

                Most members suggest Rubycon, Panasonic, and United Chemicon as good brand caps. It doesn't mean that they will never fail though.

                Originally posted by tacticalgamer
                Also, the caps say 'Rubycon' on the labels. Is this a good enough brand?
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                  #9
                  Re: Viewsonic VX724 - replaced 4 caps, still dead

                  Originally posted by tacticalgamer
                  Upon further inspection the one cap mentioned that I used to replace is actually an HSC branded one. Is this an okay brand ?
                  That 330uf 25v cap? Replace it with a good brand low ESR cap.

                  What about this other cap you said was bulged, is it a 400v cap?

                  Comment

                    #10
                    Re: Viewsonic VX724 - replaced 4 caps, still dead

                    Those CapXon caps look like Nichicon caps.
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                      #11
                      Re: Viewsonic VX724 - replaced 4 caps, still dead

                      hi guys i just registrated here because i found a thread that i was interestud of. So . the ideea is that i have olso a lcd like the one described by you and i have the flashing problem too.

                      at the moment i have changed the 2 capacitors with are marked with red, and i saw that the capacitor h154j was exploded and so Im not sure were to get it from or what value he got. "if anyone knows let me know to." and then i turn the boar up side down and i saw right under the "choper" or high voltage transformer Im not sure if its called like that... are 2 small smd transistors they are both exploded and ollso i cannot find the value or were can i get them from. and i bealive this is all the problems that this monitor with this short of problem is.
                      not in all cases thoes 2 transistors explode so to this one that you are talking about maybe them.
                      sorry for my broken english ... hope you guys understand.

                      one more thing the "high voltage transformer SPI 0451 wants to get realy realy hot: and i bealive its becase of them transiztors

                      regards
                      Attached Files

                      Comment

                        #12
                        Re: Viewsonic VX724 - replaced 4 caps, still dead

                        Hello! Welcome to the forum. I think you have a similar board to the viewsonic vx910. Please read the thread below:

                        https://www.badcaps.net/forum/showthread.php?t=9808
                        Last edited by jetadm123; 08-21-2010, 07:15 AM.

                        Comment

                          #13
                          Re: Viewsonic VX724 - replaced 4 caps, still dead

                          Originally posted by iancovm View Post
                          hi guys i just registrated here because i found a thread that i was interestud of. So . the ideea is that i have olso a lcd like the one described by you and i have the flashing problem too.

                          at the moment i have changed the 2 capacitors with are marked with red, and i saw that the capacitor h154j was exploded and so Im not sure were to get it from or what value he got. "if anyone knows let me know to." and then i turn the boar up side down and i saw right under the "choper" or high voltage transformer Im not sure if its called like that... are 2 small smd transistors they are both exploded and ollso i cannot find the value or were can i get them from. and i bealive this is all the problems that this monitor with this short of problem is.
                          not in all cases thoes 2 transistors explode so to this one that you are talking about maybe them.
                          sorry for my broken english ... hope you guys understand.

                          one more thing the "high voltage transformer SPI 0451 wants to get realy realy hot: and i bealive its becase of them transiztors

                          regards
                          I THINK I know what parts you will need, but let's be sure.

                          First, while you posted the pictures properly, they don't show the entire board. Someone else has posed an 'over-all' picture of the top, now I would like one of the bottom. Take the picture from directly overhead, macro mode, flash off, plenty of natural light (next to a window is good).

                          The circuit you are dealing with is the inverter. According to the picture in post 1, there is another identical circuit at the other end of the board. Post the numbers from the capacitor and from the transistors threre.

                          What capacitors (brand and series) did you use for 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

                            #14
                            Re: Viewsonic VX724 - replaced 4 caps, still dead

                            wow sir that was so easy )) i never had a closer loock at the board i was focusing only on the spot that is not to inpresive) and now i did find a way to fix it easyear
                            one more thing.. that capacitor h154j what is the value? and were can i get the transistors from ? im not sure if MAPLIN can provide the parts for me so i gues that i have to learn more about thoes transistors now because i havent done it when i should "at the proper time

                            i will be greatfull to anyone if i can find the answers that im looking for. the rest is up to me and a bit of luck thks guys
                            Attached Files

                            Comment

                              #15
                              Re: Viewsonic VX724 - replaced 4 caps, still dead

                              sir can you have a look here and let me know what parts i need ? pls?

                              Comment

                                #16
                                Re: Viewsonic VX724 - replaced 4 caps, still dead

                                The capacitor is a Radial Polypropolene at a value of 0.15uF(150000pF) the 'J' stands for a Tolerance of 5%,and that is important,as it must be very very similar to the other one on the Board. it is rated at 250 volts.The Transistors have on them DK QC,but unable to help you with those as I have no service manual showing a Parts list.But I'm sure someone will advise you.

                                Comment

                                  #17
                                  Re: Viewsonic VX724 - replaced 4 caps, still dead

                                  Originally posted by Rtech View Post
                                  The Transistors have on them DK QC,but unable to help you
                                  Possibly Rohm, see (or search forum for rohm)

                                  https://www.badcaps.net/forum/showth...highlight=rohm
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                                  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.

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                                  Comment

                                    #18
                                    Re: Viewsonic VX724 - replaced 4 caps, still dead

                                    Originally posted by iancovm View Post
                                    sir can you have a look here and let me know what parts i need ? pls?
                                    The transistors are Rohm 2SC4672. The Q marking indicates it is the high gain part, and the number after the Q is meaningless - it's a production code. In the USA they are available from Digikey for about $.75 each.

                                    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

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