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    #1

    Monitor Turns off after a few seconds with new caps

    I have two monitors at work, one is a 22" Viewsonic and one is a 22" Gateway. The Viewsonic had around 4 bad caps so I replaced all of them with the equivalent Panisonic FM caps. The Gateway didn't seem to have any bad caps, but I replaced mostly all of those as well. I tested all the CCFL's with an inverter from CCFL computer case lights and they all seem ok. I'm not sure where to go from here. Both monitors light up for a second then turn off. Thanks for the help
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    #2
    Re: Monitor Turns off after a few seconds with new caps

    Bad inverter transformer driver transistors take some pics of the boards and I'll circle them for you.
    Elements of the past and the future combining to make something not quite as good as either.

    Comment

      #3
      Re: Monitor Turns off after a few seconds with new caps

      Thanks
      Let me know if you need better pics
      Attached Files

      Comment

        #4
        Re: Monitor Turns off after a few seconds with new caps

        I think these are what I need? The problem is I can't find them on Mouser, or Digikey. Are these what I need, and if so any idea how to replace them?
        Attached Files

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          #5
          Re: Monitor Turns off after a few seconds with new caps

          Originally posted by TimmieT
          I think these are what I need? The problem is I can't find them on Mouser, or Digikey. Are these what I need, and if so any idea how to replace them?
          Correct me if I'm wrong but I believe those are called MOFSETs. Check Digikey.
          "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

          -Leonid Brezhnev (On the Yom Kippur War)

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            #6
            Re: Monitor Turns off after a few seconds with new caps

            Thanks for the help.
            I think your right, MOFSETs.
            I can't find any info on the part numbers, so I don't know what to order.
            Can you just buy a higher rated MOFSET, or do I need to know the voltage and other specs. If so, does anyone have a way to find some info on these parts?? Thanks for all the help.

            Comment

              #7
              Re: Monitor Turns off after a few seconds with new caps

              The parts you are calling MOSFETs probably aren't the xfmr driver transistors.
              The xfmr driver transistors are the usually the small old style 3-legged jobs.
              They basically cut power to transformer primary on-off to make it higher voltage AC.
              The drivers are the "switchers" in a SMPS.
              What you are looking at in pics are on the secondary side of xfmr.
              They take the higher voltage AC and turn it back to DC again.
              .
              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
              -
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                #8
                Re: Monitor Turns off after a few seconds with new caps

                Both of those boards probably have the drivers on the solder side as flat packs or SMD's, since I don't see them on top (but the pics are very small). I don't think they are bad, as it does work for a second or so.

                I'd be suspicious of the HV transformers, output caps (little round blue ones), or the tubes. I believe the current monitor circuit is sensing an overload and shutting them off. Also check and resolder the HV transformer connections. It's a common failure point on various makes & models of inverters.

                >>I tested all the CCFL's with an inverter from CCFL computer case lights and they all seem ok.<<
                Now try it the other way around. Try running the case lights with the inverter. Do Not run it for more than a few seconds for each tube.
                ** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **

                Can you post some larger top side pics and equally sized shots of the solder size?

                Toast
                veritas odium parit

                Comment

                  #9
                  Re: Monitor Turns off after a few seconds with new caps

                  ** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **
                  Already did that. oops
                  Hope I didn't make it more dead.
                  I don't have the rest of the monitor here, it's still at work so I'll have to try the ccfl's from the case lights on monday. Here are some better pics.
                  Thanks again for all the help from everyone.
                  Attached Files

                  Comment

                    #10
                    Re: Monitor Turns off after a few seconds with new caps

                    Originally posted by TimmieT
                    ** DO NOT RUN THE INVERTER WITHOUT THE TUBES CONNECTED **
                    Already did that. oops
                    Hope I didn't make it more dead.
                    I don't have the rest of the monitor here, it's still at work so I'll have to try the ccfl's from the case lights on monday. Here are some better pics.
                    Thanks again for all the help from everyone.
                    I've marked up the picture of the bottom of the Gateway board. The IC in the dark red circle is the inverter controller. The two ICs (actually FETs) in the bright red circles are the drivers for the inverter transformers.

                    I'd agree with PCBONEZ. The drivers are probably fine. Certainly if each output will light up a CCFL for a few seconds the drivers are good. (Note that it is difficult to determine if all four monitor CCFLs are lighting in the few seconds they are on. You have to see individual CCFLs.) The components circled in blue make up the monitor circuitry for each pair of CCFLs. The outputs of these circuits lead back to the inverter controller.

                    PlainBill
                    Attached Files
                    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

                      #11
                      Re: Monitor Turns off after a few seconds with new caps

                      Look at those cracked joints on the inverter transformers and on the CCFL output jacks! The first pin on both of those CCFL transformers looks completely cracked all around!

                      Resolder everything circled in red and go over the board with a magnifier and check for more. If I found that many from the pic I'm sure there's more.

                      This is Standard Operating Procedure for me to go over any board after I replace the defective components so I don't usually mention to check for cold joints.

                      Sheesh who runs QC on these wave soldered boards?
                      Attached Files
                      Last edited by Krankshaft; 11-08-2009, 06:43 AM.
                      Elements of the past and the future combining to make something not quite as good as either.

                      Comment

                        #12
                        Re: Monitor Turns off after a few seconds with new caps

                        Originally posted by Krankshaft
                        Look at those cracked joints on the inverter transformers and on the CCFL output jacks! The first pin on both of those CCFL transformers looks completely cracked all around!

                        Resolder everything circled in red and go over the board with a magnifier and check for more. If I found that many from the pic I'm sure there's more.

                        This is Standard Operating Procedure for me to go over any board after I replace the defective components so I don't usually mention to check for cold joints.

                        Sheesh who runs QC on these wave soldered boards?
                        QC? Krankshaft, these boards come from China!! The country where someone put melamine in baby formula to increase profits!!

                        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

                          #13
                          Re: Monitor Turns off after a few seconds with new caps

                          I'm willing to bet this is due to the lead free solder craze started by the EU many manufacturers still can't get it right.

                          Or they are using their old leaded solder equipment which isn't designed for lead free creating these joints.
                          Last edited by Krankshaft; 11-08-2009, 09:21 AM.
                          Elements of the past and the future combining to make something not quite as good as either.

                          Comment

                            #14
                            Re: Monitor Turns off after a few seconds with new caps

                            >>I'd agree with PCBONEZ. The drivers are probably fine. <<

                            veritas odium parit

                            Comment

                              #15
                              Re: Monitor Turns off after a few seconds with new caps

                              Passing credit memo to Toasty.
                              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.
                              -

                              Comment

                                #16
                                Re: Monitor Turns off after a few seconds with new caps

                                Just for informational purposes, exactly what LCD brand/model is being discussed here (and pictures posted) ?
                                There are 10 kind of people in this world: those that understand binary, and those who don't.
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                                • GeForce GT1050
                                  2 x Acer KA240H + 1 Vewsonic VP2130 21 (a cap replacement job )

                                Comment

                                  #17
                                  Re: Monitor Turns off after a few seconds with new caps

                                  The models are a Gateway HD2200 and a Viewsonic VX2255WMB

                                  Comment

                                    #18
                                    Re: Monitor Turns off after a few seconds with new caps

                                    Today I resoldered all the spots on the board other than the two small chips.
                                    Still seemed the same. I then tried to plug the tubes from the Viewsonic in and that stayed on. It seems like 3 of the 4 tubes are bad. Could a bad solder point make 3 die at the same time?(kinda dead they still light for a few seconds) I guess I need some new ccfl's. How hard are they to change? I've done a few on laptop lcd's but lately I've just replaced the whole lcd. I never get the ccf'l's to fit right and the screens always distort.

                                    I also just read this post about re-doing the solder on the end of the ccfl's
                                    https://www.badcaps.net/forum/showthread.php?t=8184

                                    Comment

                                      #19
                                      Re: Monitor Turns off after a few seconds with new caps

                                      did you ever fixed you gateway hd2200? i dont know anything about any of this but am interested in learning. this is my first time. i have same problem with this hd2200 i got for free. my power board looks a lot nicer then yours(no offense). tested all the caps to the best of my knowledge with a ddm. for some reason i focused more on the other circuit board, the one for the video and what not, since theres power and all, it just shuts off to stand by mode. notice that the biggest cap,(820uf, 25v) read upsidedown. changed it to the best of my knowledge and its still the same.

                                      sorry for such a long type. im totally new to all this. i dont even know how to solder let alone use my cheap radio shack ddm.

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                                        #20
                                        Re: Monitor Turns off after a few seconds with new caps

                                        still have this gateway hd2200, i removed the invertor hoping i could just buy it at radio shack. how naive i am. can anyone show me where i can get one ? the reason why i removed it was because it smelt burnt. really hope i can get this monitor going. thanks in advance.

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