Problems with Samsung 740N monitors

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  • alexanna
    Member
    • Mar 2010
    • 1346

    #241
    Re: Problems with Samsung 740N monitors

    I would not as a permanent repair your space is going to be very limited, you could try it far as testing goes as long as you stay with the same amperage and voltage.
    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

    Comment

    • Kampfwurst
      New Member
      • Nov 2010
      • 5

      #242
      Re: Problems with Samsung 740N monitors

      Here is my board

      http://img833.*************/img833/4456/img2622o.jpg
      http://img228.*************/img228/428/img26240.jpg
      http://img638.*************/img638/496/img2625i.jpg
      http://img831.*************/img831/1236/img2629l.jpg

      between the to point from F301 i have 800ohm. I thinks the fuse is gone

      Comment

      • Kampfwurst
        New Member
        • Nov 2010
        • 5

        #243
        Re: Problems with Samsung 740N monitors

        so i tried a glas Fuse. But still nothing. The fuse will not go again. So what can i try.

        Comment

        • retiredcaps
          Badcaps Legend
          • Apr 2010
          • 9271

          #244
          Re: Problems with Samsung 740N monitors

          Originally posted by Kampfwurst
          Here is my board
          Please attach clear focused photos using the manage attach feature so they are hosted here and do not post them inline.

          Here is an example of the composition of photos we need (top and back side of each board).

          https://www.badcaps.net/forum/showpo...94&postcount=1
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          • aze2learn
            New Member
            • Jan 2011
            • 2

            #245
            Re: Problems with Samsung 740N monitors

            I followed this thread and successfully revived my Samsung 740N after replacing 3 bulging caps 820uf 25v with 1000uf x 3 25v. Had to substitute 3A pico fuse with 3A glass fuse (with fuse cover wired nicely to the board) because I'm unable to find pico fuse here after visiting every local shop near my place. Thank you .. thank you .. thank you for all the guidance

            Comment

            • proffessor
              New Member
              • Feb 2011
              • 1

              #246
              Re: Problems with Samsung 740N monitors

              Originally posted by Kampfwurst
              i copy the picture from another Thread



              I replaece the 3 capacitor

              where is this fuse. is it the brown one next to the power plug?

              The fuse is a 3amp pico fuse.it looks like a resistor but is totally green.You cant see it in your picture because it is hidden under the white glue, near the caps you circled.

              Comment

              • Standstand
                New Member
                • Mar 2011
                • 1

                #247
                Re: Problems with Samsung 740N monitors

                Hi friends!
                I have problem with 940N... When I turn it on PC goes normally to windows, and monitor screen stays black, just power button is blinking blue. After 4-5 min desktop appears in some low resolution, so I have to change it manually (up).
                This happens ONLY if monitor is cold. It seems like it needs some warm up first...
                The same happens even if I turn off PC but no monitor, later, after few hours of pause, it will do the same 'late awakening'. If I turn monitor off when its warmed up and then make short pause, and then turn it on, it works fine. Any ideas, people?

                Comment

                • PlainBill
                  Badcaps Legend
                  • Feb 2009
                  • 7034
                  • USA

                  #248
                  Re: Problems with Samsung 740N monitors

                  Originally posted by Standstand
                  Hi friends!
                  I have problem with 940N... When I turn it on PC goes normally to windows, and monitor screen stays black, just power button is blinking blue. After 4-5 min desktop appears in some low resolution, so I have to change it manually (up).
                  This happens ONLY if monitor is cold. It seems like it needs some warm up first...
                  The same happens even if I turn off PC but no monitor, later, after few hours of pause, it will do the same 'late awakening'. If I turn monitor off when its warmed up and then make short pause, and then turn it on, it works fine. Any ideas, people?
                  Bad caps? ESR drops as a cap warms up. When the monitor was cold it was slow turning on, so Windows didn't detect it, and set the output to a low resolution.

                  Open it up and look for caps with bulging tops.

                  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

                  • Lord KiRon
                    New Member
                    • Mar 2011
                    • 4

                    #249
                    Re: Problems with Samsung 740N monitors

                    Hi guys,
                    I have 214T Samsung that first become dim, than after few hours stopped to work at all.
                    I guess first capacitors are gone, than pico fuse.
                    I opened it and it looks like 4 capacitors a blown 820uF 25v x2 and 330 uF, 25v x2.
                    So I got the capacitors and about to solder them in.
                    However I am not so sure about picofuse, I bought 135V 3A pico fuse , but the problem is that I can't locate it fuse board. I have one "suspect" (greenish thing with black "ring" in the middle) but I am not sure.
                    How I can be sure? Is there any marking on pico-fuses to distinguish them?

                    The other question, since I am not specialist in electronics, does pico-fuses have polarity? And if yes, how to tell right one?
                    The fuses I bough have no marking besides writing "LF 3A" on them.
                    Can anyone please help me?
                    Last edited by Lord KiRon; 04-08-2011, 07:16 AM.

                    Comment

                    • alexanna
                      Member
                      • Mar 2010
                      • 1346

                      #250
                      Re: Problems with Samsung 740N monitors

                      Originally posted by Lord KiRon
                      Hi guys,
                      I have 214T Samsung that first become dim, than after few hours stopped to work at all.
                      I guess first capacitors are gone, than pico fuse.
                      I opened it and it looks like 4 capacitors a blown 820uF 25v x2 and 330 uF, 25v x2.
                      So I got the capacitors and about to solder them in.
                      However I am not so sure about picofuse, I bought 135V 3A pico fuse , but the problem is that I can't locate it fuse board. I have one "suspect" (greenish thing with black "ring" in the middle) but I am not sure.
                      How I can be sure? Is there any marking on pico-fuses to distinguish them?

                      The other question, since I am not specialist in electronics, does pico-fuses have polarity? And if yes, how to tell right one?
                      The fuses I bough have no marking besides writing "LF 3A" on them.
                      Can anyone please help me?
                      I have seen these power supplies with and without a fuse for the inverter. If there is one it's usually hidden around the two schottky diodes under some glue.
                      Yes the fuses are usually marked on there body,and there is no polarity.
                      Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                      Comment

                      • retiredcaps
                        Badcaps Legend
                        • Apr 2010
                        • 9271

                        #251
                        Re: Problems with Samsung 740N monitors

                        Originally posted by Lord KiRon
                        but the problem is that I can't locate it fuse board.
                        Picofuses are usually marked PF on the PCB. For example, PF801.

                        PS. A picture of your board would help. Follow the instructions in my sig file below to attach your pictures.
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                        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

                        • Lord KiRon
                          New Member
                          • Mar 2011
                          • 4

                          #252
                          Re: Problems with Samsung 740N monitors

                          Originally posted by retiredcaps
                          Picofuses are usually marked PF on the PCB. For example, PF801.

                          PS. A picture of your board would help. Follow the instructions in my sig file below to attach your pictures.
                          Thanks.
                          please review attached images.


                          As you can see you can clearly see blown caps, but I can't locate pico fuse.
                          Attached Files

                          Comment

                          • jetadm123
                            Badcaps Legend
                            • Feb 2010
                            • 2169

                            #253
                            Re: Problems with Samsung 740N monitors

                            Originally posted by Lord KiRon
                            Thanks.
                            please review attached images.


                            As you can see you can clearly see blown caps, but I can't locate pico fuse.

                            Nice photos! Your photos justify why we ask for photos of your board. You clearly have 4 bulged caps. Replace the 6 caps, C301,C302,C107,C110,C111 and C112 with good quality caps like panasonic FM or FC series from digikey.com. You can leave the large green Samxon cap alone.
                            Last edited by jetadm123; 04-09-2011, 07:10 AM.

                            Comment

                            • retiredcaps
                              Badcaps Legend
                              • Apr 2010
                              • 9271

                              #254
                              Re: Problems with Samsung 740N monitors

                              Originally posted by Lord KiRon
                              but I can't locate pico fuse.
                              I don't see one either on the front side. Sometimes a fuse is located on the backside. Check there.
                              --- 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.

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                              • Lord KiRon
                                New Member
                                • Mar 2011
                                • 4

                                #255
                                Re: Problems with Samsung 740N monitors

                                Thanks guys, replaced the caps and it works.
                                However somehow it's not too bright , I mean it's not dim like it was before it died, it's rather OK, but brightness 100% gives about same brightness as 40-50% before. Quite usable but this a bit strange.

                                Comment

                                • jetadm123
                                  Badcaps Legend
                                  • Feb 2010
                                  • 2169

                                  #256
                                  Re: Problems with Samsung 740N monitors

                                  Originally posted by Lord KiRon
                                  Thanks guys, replaced the caps and it works.
                                  However somehow it's not too bright , I mean it's not dim like it was before it died, it's rather OK, but brightness 100% gives about same brightness as 40-50% before. Quite usable but this a bit strange.
                                  Have you verified all the CCFL's are lit and are at equal brightness?

                                  Comment

                                  • skystormfarms
                                    Banned
                                    • Mar 2011
                                    • 160

                                    #257
                                    Re: Problems with Samsung 740N monitors

                                    dose any body see it runs hot

                                    Comment

                                    • Lord KiRon
                                      New Member
                                      • Mar 2011
                                      • 4

                                      #258
                                      Re: Problems with Samsung 740N monitors

                                      Originally posted by jetadm123
                                      Have you verified all the CCFL's are lit and are at equal brightness?
                                      The brightness is equal, so I guess all CCFL's are lit.

                                      Comment

                                      • miguelangel
                                        New Member
                                        • May 2011
                                        • 1

                                        #259
                                        Re: Problems with Samsung 740N monitors

                                        Greetings I had a similar problem to those who are posing here with the 740N model. did not want to turn. will replace the 1000uf capacitors 25volts but not working.The problem was in the small board where is the power button.
                                        Good luck.

                                        Comment

                                        • blakmajik
                                          New Member
                                          • Jan 2011
                                          • 1

                                          #260
                                          Re: Problems with Samsung 740N monitors

                                          So after reading over this thread, and replacing both the caps and the fuse, my search lead to shorted fets. I ordered new parts, and now that they have arrived, I can't find the board. I think it's been recycled, I looked everywhere for it.



                                          Any suggestions on a replacement inverter for the 740B? lol

                                          Comment

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