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    #1

    Samsung SyncMaster 731N Screen on and off.

    I have a Samsung SyncMaster 731N. The Monitor will turn on for about 15-20 seconds, then the screen will go off for 1-2 seconds, and then back on... this happens over and over. The amount of time it is on varies. The power board is labeled: ILPI-013. I found someone else with a problem with this same monitor, but different issues:

    https://www.badcaps.net/forum/showth...highlight=731n

    I've tested all the voltages that he was asked to check.

    I'm getting 150VDC at the filter cap
    I'm getting 5.18VDC out from the power board, going to the logic board. This is pins 1 and 2 on connector.
    I get 3.23VDC at pin 5 for ON/OFF (believe this is coming from the logic board to tell the power board to start the lamps?
    At U101 on the logic board I'm getting the 3.3VDC that the VR is suppose to put out
    At U102 on the logic board I'm getting the 1.8VDC that the VR is suppose to put out.

    When the screen goes off... All voltages that I've mentioned are steady. I've replaced Caps C812 and C808. I will be recapping the entire board, but this is all I have on hand at this time. There was no change after replacing these two caps.

    Is there a way to watch the voltage going to the inverter section? So when the lamps go off, I can see if it is dropping?

    The pics I've posted are from the other tread... I do not have my camera handy, but my boards are the same. There are no browning/burnt areas at all.
    Attached Files
    Tags: None
    #2
    Re: Samsung SyncMaster 731N Screen on and off.

    Originally posted by billy66 View Post
    I have a Samsung SyncMaster 731N. The Monitor will turn on for about 15-20 seconds, then the screen will go off for 1-2 seconds, and then back on... this happens over and over. The amount of time it is on varies. The power board is labeled: ILPI-013. I found someone else with a problem with this same monitor, but different issues:

    https://www.badcaps.net/forum/showth...highlight=731n

    I've tested all the voltages that he was asked to check.

    I'm getting 150VDC at the filter cap
    I'm getting 5.18VDC out from the power board, going to the logic board. This is pins 1 and 2 on connector.
    I get 3.23VDC at pin 5 for ON/OFF (believe this is coming from the logic board to tell the power board to start the lamps?
    At U101 on the logic board I'm getting the 3.3VDC that the VR is suppose to put out
    At U102 on the logic board I'm getting the 1.8VDC that the VR is suppose to put out.

    When the screen goes off... All voltages that I've mentioned are steady. I've replaced Caps C812 and C808. I will be recapping the entire board, but this is all I have on hand at this time. There was no change after replacing these two caps.

    Is there a way to watch the voltage going to the inverter section? So when the lamps go off, I can see if it is dropping?

    The pics I've posted are from the other tread... I do not have my camera handy, but my boards are the same. There are no browning/burnt areas at all.
    L802 appears to be the filter for the inverter. It's near the center of the picture of the back of the power supply.

    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: Samsung SyncMaster 731N Screen on and off.

      Thanks PlainBill.

      L802 to ground is 14.1VDC when on, and 15.1VDC when screen is off.

      L803 to ground is 5.1VDC when on, and 5.0VDC when screen is off.

      Any idea where to go now? Is 15VDC right?

      Comment

        #4
        Re: Samsung SyncMaster 731N Screen on and off.

        Originally posted by billy66 View Post
        The Monitor will turn on for about 15-20 seconds, then the screen will go off for 1-2 seconds, and then back on... this happens over and over. The amount of time it is on varies.
        If you point a fan to the backside, does the LCD stay on longer? Any poor looking solder joints?

        I'm getting 150VDC at the filter cap
        This could be a wild goose chase, but (mains * 1.4) => (110V * 1.4) = 154V DC. 150V DC seems a tad low.
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        Comment

          #5
          Re: Samsung SyncMaster 731N Screen on and off.

          I will try the fan, though the problem is with the monitor all opened up, and the boards just stilling in the open air... but I will try the fan.

          I know that the 150V seems low... but every monitor I've checked is low... could be my supply? House is around 109-110VAC. If that is the issue, what could I check?

          Comment

            #6
            Re: Samsung SyncMaster 731N Screen on and off.

            Originally posted by billy66 View Post
            I will try the fan, though the problem is with the monitor all opened up, and the boards just stilling in the open air... but I will try the fan.
            I saw this video 4 or 5 months ago which led me to suggest the fan ...

            http://www.youtube.com/watch?v=rePrm5JHjhc

            I know that the 150V seems low... but every monitor I've checked is low... could be my supply? House is around 109-110VAC.
            109V * 1.4 = 152.6. If other working monitors measure 150V, then I would not worry about it.
            --- 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.

            --- end sig file ---

            Comment

              #7
              Re: Samsung SyncMaster 731N Screen on and off.

              Originally posted by billy66 View Post
              Thanks PlainBill.

              L802 to ground is 14.1VDC when on, and 15.1VDC when screen is off.

              L803 to ground is 5.1VDC when on, and 5.0VDC when screen is off.

              Any idea where to go now? Is 15VDC right?
              Those voltages APPEAR to be right. I note that the backlight control line does not change, which means the inverter controller is shutting down, but it is not latching. Very strange, most of them latch off if shut down by an error condition. What is the part number of the 16 pin IC on the bottom of the board.

              I'm going to warn you that it will be virtually impossible to assist you in troubleshooting this without better pictures.

              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

                #8
                Re: Samsung SyncMaster 731N Screen on and off.

                Thanks retiredcaps, I'll try the fan... see if it lasts longer.

                PlainBill... I'm aware of my lack of good pics, but I was at work with the monitor today... no access to camera. I'll bring in my camera tomorrow and take a couple of good pics. I just didn't want to waste a day of troubleshooting... as my lunch break gave me the free time to work on it. You've been a help to me before, and I wont let you down on the pic

                Comment

                  #9
                  Re: Samsung SyncMaster 731N Screen on and off.

                  Hope these pictures are better.

                  The 16pin chip on the back of the power board is IC501
                  0Z9938GN
                  A64NRA 2G
                  0626B

                  I'll try the fan test in a little bit.
                  Attached Files

                  Comment

                    #10
                    Re: Samsung SyncMaster 731N Screen on and off.

                    Fan test didn't change the results... on/off the same.

                    Not sure if this matters... but the on/off isn't always the same timing... might go like this:

                    On 7 seconds
                    Off 2 seconds
                    On 2 seconds
                    Off 2 seconds
                    On 2 seconds
                    Off 2 seconds
                    On 7 seconds
                    Off 1 second
                    On 1 second

                    no set rhyme to the reason.

                    Comment

                      #11
                      Re: Samsung SyncMaster 731N Screen on and off.

                      Originally posted by billy66 View Post
                      Fan test didn't change the results... on/off the same.

                      Not sure if this matters... but the on/off isn't always the same timing... might go like this:

                      On 7 seconds
                      Off 2 seconds
                      On 2 seconds
                      Off 2 seconds
                      On 2 seconds
                      Off 2 seconds
                      On 7 seconds
                      Off 1 second
                      On 1 second

                      no set rhyme to the reason.
                      First of all, I'm assuming at this point that the backlights are turning on and off. Please verify that this is the case. If so, it's time to do a little research. You'll have to set this up so all CCFLs are connected, the monitor is plugged in and connected to a signal source.

                      See if changes at any of these pins on the OZ9938GN correspond to the display changing. Report the voltage at each pin. Rather than trying to probe each pin, it may be easier to probe the end of a capacitor, resistor, or jumper connected to the pin.

                      Pin 2 VDDA

                      Pin 4 Dim

                      Pin 5 Isen

                      Pin 6 Vsen

                      Pin 7 OVPT

                      Pin 10 Ena

                      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

                        #12
                        Re: Samsung SyncMaster 731N Screen on and off.

                        Originally posted by PlainBill View Post
                        First of all, I'm assuming at this point that the backlights are turning on and off. Please verify that this is the case. If so, it's time to do a little research. You'll have to set this up so all CCFLs are connected, the monitor is plugged in and connected to a signal source.

                        See if changes at any of these pins on the OZ9938GN correspond to the display changing. Report the voltage at each pin. Rather than trying to probe each pin, it may be easier to probe the end of a capacitor, resistor, or jumper connected to the pin.

                        Pin 2 VDDA

                        Pin 4 Dim

                        Pin 5 Isen

                        Pin 6 Vsen

                        Pin 7 OVPT

                        Pin 10 Ena

                        PlainBill
                        Yes, the monitor comes on completely, screen lights and all. Then when it shuts off, the screen goes dark (CCFLs go off) but the power LED stays green.

                        IC501
                        Pin 2 VDDA - 4.86VDC on and 4.96VDC off
                        Pin 4 Dim - 0.85VDC on and off
                        Pin 5 Isen - 1.03VDC on and 0.01VDC off
                        Pin 6 Vsen - 0.73VDC on and 0.00VDC off
                        Pin 7 OVPT - 1.90VDC on and 0.30 off
                        Pin 10 Ena - 2.47VDC on and 0.01VDC off

                        All CCFLs were plugged in and monitor was connected to a signal source for this test.

                        Comment

                          #13
                          Re: Samsung SyncMaster 731N Screen on and off.

                          Originally posted by billy66 View Post
                          Yes, the monitor comes on completely, screen lights and all. Then when it shuts off, the screen goes dark (CCFLs go off) but the power LED stays green.

                          IC501
                          Pin 2 VDDA - 4.86VDC on and 4.96VDC off
                          Pin 4 Dim - 0.85VDC on and off
                          Pin 5 Isen - 1.03VDC on and 0.01VDC off
                          Pin 6 Vsen - 0.73VDC on and 0.00VDC off
                          Pin 7 OVPT - 1.90VDC on and 0.30 off
                          Pin 10 Ena - 2.47VDC on and 0.01VDC off

                          All CCFLs were plugged in and monitor was connected to a signal source for this test.
                          Trace this back to the connector to the logic board. The inverter is being switched off, then back on. Relevant components are J505, R501, D501 C518 and R518. It appears R501 has a crack across it, but it couldn't be that simple. Probably something complex like a bad solder joint.

                          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: Samsung SyncMaster 731N Screen on and off.

                            Originally posted by PlainBill View Post
                            Trace this back to the connector to the logic board. The inverter is being switched off, then back on. Relevant components are J505, R501, D501 C518 and R518. It appears R501 has a crack across it, but it couldn't be that simple. Probably something complex like a bad solder joint.

                            PlainBill
                            R501 tests at 100k... which is its rating. Should I resolder those components you mentioned?

                            Comment

                              #15
                              Re: Samsung SyncMaster 731N Screen on and off.

                              Originally posted by billy66 View Post
                              R501 tests at 100k... which is its rating. Should I resolder those components you mentioned?
                              Yes. IIRC, you indicated the ON/Off line from the logic board stays high consistently. But the voltage at the inverter controller is changing. As far as I can determine, the components I mentioned are the only components involved.

                              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

                                #16
                                Re: Samsung SyncMaster 731N Screen on and off.

                                Originally posted by PlainBill View Post
                                Yes. IIRC, you indicated the ON/Off line from the logic board stays high consistently. But the voltage at the inverter controller is changing. As far as I can determine, the components I mentioned are the only components involved.

                                PlainBill
                                OK, thanks PlainBill. I will remove and test those components. Thanks for the help!

                                By the way, what does "IIRC" mean?

                                Comment

                                  #17
                                  Re: Samsung SyncMaster 731N Screen on and off.

                                  Originally posted by billy66 View Post
                                  OK, thanks PlainBill. I will remove and test those components. Thanks for the help!

                                  By the way, what does "IIRC" mean?
                                  http://www.urbandictionary.com/define.php?term=iirc

                                  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

                                    #18
                                    Re: Samsung SyncMaster 731N Screen on and off.

                                    Hi, my 710N had the same problem as described here, i resoldered the PSU/inverter board, seems did fix the sreen on and off problem.

                                    Now the issue is that monitor goes black when windows start
                                    Attached Files
                                    Last edited by uligli; 10-07-2010, 04:02 PM.

                                    Comment

                                      #19
                                      Re: Samsung SyncMaster 731N Screen on and off.

                                      Originally posted by uligli View Post
                                      Hi, my 710N had the same problem as described here, i resoldered the PSU/inverter board, seems did fix the sreen on and off problem.

                                      Now the issue is that monitor goes black when windows start
                                      You resoldered the entire board? Every component? Or just the ones described above?

                                      Comment

                                        #20
                                        Re: Samsung SyncMaster 731N Screen on and off.

                                        Originally posted by billy66 View Post
                                        You resoldered the entire board? Every component? Or just the ones described above?
                                        I resoldered the entire board.

                                        Comment

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