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Samsung 930b LCD cold start problem (inverter?)

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    #61
    Re: Samsung 930b LCD cold start problem (inverter?)

    Originally posted by demens View Post
    Noone has mentioned replacing that 2nd one.
    Post #47 and #50 both suggest replacing ALL.

    That purple can is 25V which suggests that it might help provide DC voltage to one or both of the inverter transformer (can't be sure without tracing the circuit or seeing a schematic).
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      #62
      Re: Samsung 930b LCD cold start problem (inverter?)

      Well, i replaced the one closest to the pack. Tested it again, powering up the board without the rest of the monitor connected to it this time. Same hissing sound, now only 2 minutes.

      Replaced that last lonely one, didn't bother testing anymore, just re-assembled the monitor. Turn it on, no hissing, monitor works.

      Conclusion, listen to the advice here, replace EVERY SINGLE cap on the board and not just the one that looks bad.

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        #63
        Re: Samsung 930b LCD cold start problem (inverter?)

        Originally posted by demens View Post
        Conclusion, listen to the advice here, replace EVERY SINGLE cap on the board and not just the one that looks bad.
        When PlainBill gets burned (from post #50 again) ...

        Originally posted by PlainBill
        I tried to save money on a Gateway monitor. I didn't replace a couple of caps because 'they looked good'. It wasn't until I found this site that I learned that the $.28 cap I didn't replace was the reason the monitor still wasn't working.
        everyone surely will.
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          #64
          Re: Samsung 930b LCD cold start problem (inverter?)

          Originally posted by demens View Post
          Well, i replaced the one closest to the pack. Tested it again, powering up the board without the rest of the monitor connected to it this time. Same hissing sound, now only 2 minutes.

          Replaced that last lonely one, didn't bother testing anymore, just re-assembled the monitor. Turn it on, no hissing, monitor works.

          Conclusion, listen to the advice here, replace EVERY SINGLE cap on the board and not just the one that looks bad.
          There are 10 kind of people in this world: those that understand binary, and those who don't.
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            #65
            Re: Samsung 930b LCD cold start problem (inverter?)

            I have a Samsung 930B monitor which started having the same symptoms as the original first post of this thread. The monitor started taking a long time to display any picture and the green power led started blinking rapidly, much faster than when the led was normally blinking in power saving mode. Eventually, it will not display any image at all, the power led just blinks rapidly, none of the buttons on the monitor respond, and no OSD is displayed. I have taken apart the circuit board and attached photos. Can anyone verify if it is the same bad capacitor problem? If so, which replacements should I obtain? Is digikey the recommended source for replacements?

            http://img26.*************/g/img4136e.jpg/
            Attached Files

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              #66
              Re: Samsung 930b LCD cold start problem (inverter?)

              Originally posted by BeastGTS View Post
              Eventually, it will not display any image at all, the power led just blinks rapidly, none of the buttons on the monitor respond, and no OSD is displayed.
              1) Do you see the display if you shine a flashlight at it?

              2) Well, the caps look visually okay, but they could still be bad. Let's assume, for now, they are good and start with measuring voltages.

              3) If you have a multimeter, take voltages readings on the connector between power board and the logic board. You should get 5V DC on least one of the pins and possibly 12V or 19V DC as well.

              4) If you don't see the voltages above, then carefully measure the DC voltage across the large main capacitor. Careful, it is mains * 1.4 voltage.

              5) Also, you may have to desolder that green board that is upside down to get a picture. One person had a problem with a Samsung monitor about 5 weeks ago and it was a component on that board that was the problem.

              6) There is also a red fuse right next to the green board. Check to make sure the fuse reads less than 1.0 ohms.
              Last edited by retiredcaps; 09-25-2010, 06:10 PM.
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                #67
                Re: Samsung 930b LCD cold start problem (inverter?)

                I have this same monitor and had atleast 3 of the 820uf 25v CapXon the visually looked bad so I replaced with 1000uf 25v velleman caps, there was also a 1000uf 10v that looked bad so I replaced it also with the same 1000uf 25v velleman and still can see the check signal cable moving around on the screen when I shine a flashlight at it but even after letting it set plugged in for more than 20 min the screen never gets any brighter any suggestions?

                Comment

                  #68
                  Tech details on green fuse?

                  In case somebody cares, i just wanted to point out the procedure described earlier in the first posts also works with a faulty Samsung 930BF. Apparantly the PCB-Layout isnt much different and the problems are the same.

                  But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it? I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...

                  Comment

                    #69
                    Re: Samsung 930b LCD cold start problem (inverter?)

                    Originally posted by tts2271
                    But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it?
                    I think it's a 3A fuse. See post #26 and the post after on page 2 of this thread.

                    Originally posted by tts2271
                    I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...
                    It won't affect the circuit in a bad way if everything continues to work properly. However, if one of the transistors in the inverter shorts, the whole power supply could get damaged. So with that said, better replace that wire with a proper fuse.

                    Originally posted by RussTime View Post
                    I have this same monitor and had atleast 3 of the 820uf 25v CapXon the visually looked bad so I replaced with 1000uf 25v velleman caps, there was also a 1000uf 10v that looked bad so I replaced it also with the same 1000uf 25v velleman and still can see the check signal cable moving around on the screen when I shine a flashlight at it but even after letting it set plugged in for more than 20 min the screen never gets any brighter any suggestions?
                    You need to use low ESR caps. The velleman caps you used most likely aren't.
                    Stick to the good brands like Rubycon, United Chemicon, Panasonic, Nichicon, and Sanyo. As for what series to use from these brands:
                    From Rubycon, you can use YXG, ZL, and even MBZ
                    United Chemicon - KY, KZE, LXY, and LXZ
                    Panasonic - FC, FR, FK, and FM
                    Nichicon - PM, PW, HE, and HD
                    Sanyo - WX
                    Also check fuse F301.

                    Comment

                      #70
                      definately check fuse F301!

                      Yes, especially check the fuse F301!

                      It was the same with my 930BF, changing the 820uF capacitors only brought back the picture with no backlight. After wiring the fuse the backlight came on and the whole display came back to life. Great thing!

                      Comment

                        #71
                        Re: Samsung 930b LCD cold start problem (inverter?)

                        I have the same monitor as mentioned in this thread. My symptoms are the green light comes on.. never blinks..just remains solid green. however if you push one of the other buttons.. menu etc.. you can see a faint flicker of light thru out the panel.. hard to see unless its dark... I guess I should start with the fuse?

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                          #72
                          Re: Samsung 930b LCD cold start problem (inverter?)

                          also having a hard time locating the fuse. I viewed images of board posted and mine seems to be a bit different.. would this fuse be next to my caps? I noticed the tops of 3 caps are humped up compared to the rest of the caps.

                          Comment

                            #73
                            Re: Samsung 930b LCD cold start problem (inverter?)

                            Originally posted by Logicsays View Post
                            also having a hard time locating the fuse. I viewed images of board posted and mine seems to be a bit different.. would this fuse be next to my caps? I noticed the tops of 3 caps are humped up compared to the rest of the caps.
                            Forget the fuse. Replace the caps!!!!

                            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.

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                              #74
                              Re: Samsung 930b LCD cold start problem (inverter?)

                              Originally posted by PlainBill View Post
                              Forget the fuse. Replace the caps!!!!

                              PlainBill
                              Thanks.. I ordered them yesterday. I'll let ya know how it turns out.

                              Comment

                                #75
                                Re: Samsung 930b LCD cold start problem (inverter?)

                                I replaced the three bulged caps.. no change. Solid green light nothing else.

                                Comment

                                  #76
                                  Re: Samsung 930b LCD cold start problem (inverter?)

                                  1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

                                  2) What brand and series did you use for replacements?

                                  3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?
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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.

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                                  Comment

                                    #77
                                    Re: Tech details on green fuse?

                                    Originally posted by tts2271 View Post
                                    In case somebody cares, i just wanted to point out the procedure described earlier in the first posts also works with a faulty Samsung 930BF. Apparantly the PCB-Layout isnt much different and the problems are the same.

                                    But has somebody managed to identify exactly the little green fuse? or at least has more technical specs about it? I just shortend it with a wire instead and it works, hope that wont affect the other circuits in a bad way...
                                    Where is this fuse? My board looks identical to the images in post #60 Is it right next to the 3 caps in the white rubber goo?

                                    Comment

                                      #78
                                      Re: Samsung 930b LCD cold start problem (inverter?)

                                      Originally posted by retiredcaps View Post
                                      1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

                                      2) What brand and series did you use for replacements?

                                      3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?
                                      I replaced the caps with the mentioned digikeys replacements. I'll try to the flash light trick again before the caps being replaced I had nothing. I'll update

                                      Comment

                                        #79
                                        Re: Samsung 930b LCD cold start problem (inverter?)

                                        Originally posted by retiredcaps View Post
                                        1) Post clear focused pictures of your boards using the manage attachments function. Please do not post inline.

                                        2) What brand and series did you use for replacements?

                                        3) If the power LED is on, hookup a working computer displaying your favourite wallpaper. If you shine a flashlight on the screen, do you see the wallpaper?
                                        The image is viewable with a flash light.. so something is working..

                                        Comment

                                          #80
                                          Re: Tech details on green fuse?

                                          Originally posted by Logicsays View Post
                                          My board looks identical to the images in post #60
                                          Can we get clear and focused picture of YOUR boards? Referencing other people's pictures doesn't help us diagnose YOUR problem. Your board could have unique characteristics not shown in someone else's photo like a charred resistor or suspicious looking transistor.

                                          It is not uncommon for manufacturers to make changes on their boards. Also try to get the resolution as close to 2000x2000 as possible.
                                          Last edited by retiredcaps; 02-15-2011, 06:14 PM.
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