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    #1

    Samsung Syncmaster 930B - screen going off and on

    Hello,

    My monitor screen blinks off for a second or two every 10-15 seconds or so. Before purchasing a new monitor I decided to browse the internet for possible causes - after reading a variety of information including info on badcaps it seemed to me that it was probably a bad capacitor or two. I have opened up the monitor now and removed the board with the capacitors. However, the capacitors are not showing any visible signs of problem. The tops of them are all nice and flat, the capacitors are straight with no bulging anywhere nor are they leaking anything. They look pretty much perfect. Is it likely that my screen problem is something else - should I be checking something different.

    I am by no means an expert on these things so any assistance or direction that anyone could provide me would be greatly appreciated. Thank you!
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    #2
    Re: Samsung Syncmaster 930B - screen going off and on

    Originally posted by jay333 View Post
    My monitor screen blinks off for a second or two every 10-15 seconds or so.
    This could be bad ccfls or bad ccfl return wiring. See

    http://s807.photobucket.com/albums/y...klight%20lamp/

    It could also be bad caps or a bad inverter transformer. See

    https://www.badcaps.net/forum/showpo...21&postcount=2
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      #3
      Re: Samsung Syncmaster 930B - screen going off and on

      Thank you for this great information. It is most helpful. I have read through everything carefully and after further watching of my problem I believe I am correct to say that it isn't the '2 second to black' issue. I didn't realized this before but my green power light goes off when the monitor flashes off. So, every 6 seconds the screen flashes off and on again for probably less than a second. When it does the green power light also goes off (and comes back on again).

      As noted earlier I have taken the monitor apart only to find that the capacitors look absolutely perfect (as does everything else). I'm hoping that the fact the power light is also going off/on provides a more definite reason for the problem.

      As always, any direction that can be provided is greatly appreciated. Thank you.

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        #4
        Re: Samsung Syncmaster 930B - screen going off and on

        Originally posted by jay333 View Post
        As always, any direction that can be provided is greatly appreciated. Thank you.
        Mabye check the soldering? If anything looks dodgy, you may want to reflow it.

        Also, it would help if you post pictures in the "preferred" format as described in the guide above (see misc suggestion #1).
        Last edited by retiredcaps; 10-24-2011, 11:23 PM.
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          #5
          Re: Samsung Syncmaster 930B - screen going off and on

          Hello,

          I took the monitor apart again and took some pictures. I took a number of photos (front and back of the main board where the capacitors are) and also a front/back picture of the other board in the monitor (where the power and monitor plug into). I am certainly no expert but everything looks quite good to me. And, the capacitors look perfect. Again, the screen goes off for a split second every 6 seconds (when it does the power light goes off as well). Any assistance/advice greatly appreciated. Thank you!
          Attached Files

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            #6
            Re: Samsung Syncmaster 930B - screen going off and on

            Originally posted by jay333 View Post
            And, the capacitors look perfect.
            1) Read this thread by our fellow Canadian, smason.

            https://www.badcaps.net/forum/showthread.php?p=163015

            2) Your board also uses Samxon GF caps.

            Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300. (Refer back to #1).

            3) There are some solder joints that have ring cracks. I circled the most obvious in red. I would touch up all the dodgy looking joints. If the problem persists, then you can try replacing the caps with something like Panasonic FR or FM series.
            Attached Files
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              #7
              Re: Samsung Syncmaster 930B - screen going off and on

              Thank you so much for your assistance. Can you give me some direction on how to best touch up the joints. I read somewhere where you can reflow such joints by putting the whole board in the oven - doesn't sound like a good idea to me! Should i just reheat each joint with a soldering gun (until it softens) or do i add solder? Thanks.

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                #8
                Re: Samsung Syncmaster 930B - screen going off and on

                Originally posted by jay333 View Post
                Should i just reheat each joint with a soldering gun (until it softens) or do i add solder?
                1) You can reheat each joint until it goes into liquid state and then remove your solder gun/iron.

                2) You can remove the old solder completely and add new solder.

                3) You can reheat each joint and add a bit of new solder.

                I have done all 3 at various points and I don't have a preference, but some would suggest #2 is the most reliable.
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                  #9
                  Re: Samsung Syncmaster 930B - screen going off and on

                  I completely forgot to ask for DC voltage measurements on CN603. If you have a multimeter, measure all the pins on CN603 with respect to ground (say a ground screw).

                  List all the pins and what it says on the legend. Measure each pin multiple times as the lcd goes on/off.
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                    #10
                    Re: Samsung Syncmaster 930B - screen going off and on

                    OK, I have redone many joints on the board. I have also just replaced the capacitors. Unfortunately, the screen still goes off for a split second every 6 seconds (and the power light goes off as well). Any other suggestions that I could look at? Is the fact that the power light also goes off any sort of a clue?

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                      #11
                      Re: Samsung Syncmaster 930B - screen going off and on

                      As soon as I see one of these little sub pcb's mounted on the top of a PSU/Inverter,I cringe and approach the 'fault' in a different manner,as these regularly fail, as they carry the Backlight drivers etc. To fault find them is usually not feasible,and to replace them in total...no chance,so I do not change caps as a first immediate action,until I am certain that this PCB sems OK,that means measuring voltages(as suggested by retired caps),ensuring the BL On signal is functional,and removing the power to the sub pcb if possible,and then see if the power lamp stays on.

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                        #12
                        Re: Samsung Syncmaster 930B - screen going off and on

                        Originally posted by jay333 View Post
                        OK, I have redone many joints on the board. I have also just replaced the capacitors. Unfortunately, the screen still goes off for a split second every 6 seconds (and the power light goes off as well). Any other suggestions that I could look at? Is the fact that the power light also goes off any sort of a clue?
                        The power light is indeed a clue. It would appear the processor on the signal card may be momentarily turning off the power led and inverter. Jay333 has already mentioned checking the BL_ON (or equivalent) signal.

                        Excuse me if you have already done so, but you should also be examining the power line (5V?) to the signal card, the outputs of the LDO regulators on the signal card, and even the reset controller (if any) on the signal card. Don't forget the input signal itself - you may want to make sure it is a plain vanilla 640 x 480 @ 60hz

                        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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                          #13
                          Re: Samsung Syncmaster 930B - screen going off and on

                          Originally posted by PlainBill View Post
                          Excuse me if you have already done so, but you should also be examining the power line (5V?) to the signal card, the outputs of the LDO regulators on the signal card, and even the reset controller (if any) on the signal card.
                          I did ask for voltage readings back in post #9 (3 minutes after I answered the reflow question), but perhaps the OP didn't see the message?

                          All the suggestions by Rtech and PlainBill were next on the list of things to examine. It looks like 2 voltage regulators on the signal card. One is -33 and the other is -18.
                          Last edited by retiredcaps; 11-03-2011, 08:04 AM.
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                            #14
                            Re: Samsung Syncmaster 930B - screen going off and on

                            Originally posted by Rtech View Post
                            As soon as I see one of these little sub pcb's mounted on the top of a PSU/Inverter,I cringe.
                            This is the only case that I remember participating in that had something bad on those little sub pcbs. Luckily we were able to help the OP get it fixed. It too was a Samsung.

                            https://www.badcaps.net/forum/showthread.php?t=10493
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                              #15
                              Re: Samsung Syncmaster 930B - screen going off and on

                              Originally posted by retiredcaps View Post
                              This is the only case that I remember participating in that had something bad on those little sub pcbs. Luckily we were able to help the OP get it fixed. It too was a Samsung.

                              https://www.badcaps.net/forum/showthread.php?t=10493
                              Out of qty 10 I have seen,4 of them have been faulty,and not all Samsung.....now you may see why I 'cringe'

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                                #16
                                Re: Samsung Syncmaster 930B - screen going off and on

                                The one Samsung 931B I've worked on had a very similar power supply. That one had a bad inverter transformer.

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                                  #17
                                  Re: Samsung Syncmaster 930B - screen going off and on

                                  How do i go about measuring the voltages on CN603? What is CN603?

                                  Comment

                                    #18
                                    Re: Samsung Syncmaster 930B - screen going off and on

                                    Originally posted by jay333 View Post
                                    How do i go about measuring the voltages on CN603? What is CN603?
                                    Instructions given in post #9. CN603 is the pcb designation on you board. It is the connector.
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