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    Samsung 731N menu keeps popping up

    First let me thank all of you for such a terrific forum.

    In my recent Craigslist score, this was the smallest of the three for $20 deal. I'm awaiting caps for the other 2, but this one acted differently.

    Out of the box, when booting the monitor, the green status light would flash more quickly than normal, then one couldn't turn the unit off reliably. The "check cable" box moved about on the screen as I didn't have the VGA attached. I noted on opening the bezel that the ribbon cable to the front buttons seemed to fall away too easily. Re-attached the button board, still same problem. Opened it up and inspection shows nothing obvious o/t the ribbon to the buttons seems to have one more right angle fold than needed to reach the button board and still lay flat.

    Reflowed all (ugh) joints on the back of the logic board and the PS/inverter board. Reflowed the transistors on the front of the logic board, but other connections looked okay and those are really small even for my Hakko. Still no joy.

    Connected to a computer, I see a fabulous image with a random dance of the monitor's menu all the time.

    Tugging on the button board does nothing, reflowing the board, nothing, de-soldering the menu button and reboot, nothing; all resistors on the button board are okay; reseated all cables, nothing. Once the monitor is up, if I disconnect the button board, the menu disappears and all appears normal (I may not have supposed to do that, but so far so good). Haven't traced the continuity of the button cable while flexing it, but am wondering what I'm missing?
    Attached Files
    Last edited by romansroad; 12-11-2010, 01:12 PM.

    #2
    Re: Samsung 731N menu keeps popping up

    Try checking the continuity of each pushbutton switch on the board. Maybe one of them is shorted.

    Possibly a bad ribbon cable?

    Also check the resistors/caps that located at the other end of the pushbutton cable on the logic board.
    Last edited by jetadm123; 12-11-2010, 01:41 PM.

    Comment


      #3
      Re: Samsung 731N menu keeps popping up

      Cable continuity is good, even with flexing the cable. Reflowed the tiny SMD's on the cable side of the logic board. All caps look okay, and all switches are good. I didn't check the SMD caps for obvious reasons. I don't have a replacement cable, but could make one...... Any other ideas?

      Comment


        #4
        Re: Samsung 731N menu keeps popping up

        Was hoping someone would jump in on this....as I've not seen this problem before, but it has no doubt happened to someone. Thanks!

        Comment


          #5
          Re: Samsung 731N menu keeps popping up

          Had this on a 720 but that was because the switch board had warped and the switches were touching the lcd frame
          Replaced switches and insulated screen
          But yours is doing it with the control out of the case maybe change switches and see what happens

          Comment


            #6
            Re: Samsung 731N menu keeps popping up

            Different monitor, but info troubleshooting the switch board may pertain to you.

            https://www.badcaps.net/forum/showth...agent24&page=2

            Comment


              #7
              Re: Samsung 731N menu keeps popping up

              I am thinking about this also, a lot of monitors will power on without the front panel switch hooked up.
              [ IF the monitor is powered down by pulling the AC power cord.]
              If you haven’t already try it without the front panel hooked up.It may or may not make a difference
              Al.
              TRy to power down when the menu is not being displayed.
              Last edited by alexanna; 12-14-2010, 10:29 AM. Reason: added something
              Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

              Comment


                #8
                Re: Samsung 731N menu keeps popping up

                Thanks and I'll try the cable pull when I get home. It does continue to work when the unit is up and I pull the cable

                Comment


                  #9
                  Re: Samsung 731N menu keeps popping up

                  Al, you are so right!.

                  Very interesting. When I disconnect the button board, all is well. The monitor powers up (backlights) when the computer boots, and the display is crisp. When shutting down, the monitor turns off after the computer shuts down, and the backlights switch off. All I lose is panel adjustments.

                  Would still like to figure this out, though, if there are any ideas on how to repair it completely. I could build a new cable....but somehow I wonder if the problem is at the logic board end.

                  Comment


                    #10
                    Re: Samsung 731N menu keeps popping up

                    Did you disconnect the ribbon from the logic board or the switch panel?
                    Al.
                    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                    Comment


                      #11
                      Re: Samsung 731N menu keeps popping up

                      Originally posted by romansroad View Post
                      Al, you are so right!.

                      Very interesting. When I disconnect the button board, all is well. The monitor powers up (backlights) when the computer boots, and the display is crisp. When shutting down, the monitor turns off after the computer shuts down, and the backlights switch off. All I lose is panel adjustments.

                      Would still like to figure this out, though, if there are any ideas on how to repair it completely. I could build a new cable....but somehow I wonder if the problem is at the logic board end.
                      The service manual is at Elektrotanya. This seems to use the multi-voltage approach to communicating between the front panel and the logic card. Compare the voltages at pins 2 and 3 of CN200 with the cable connected and with it disconnected. Clue: The monitor works properly with the cable disconnected. The cable seems to be perfect. QED: The problem is on the front panel card.

                      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 731N menu keeps popping up

                        Originally posted by PlainBill View Post
                        QED: The problem is on the front panel card.PlainBill
                        Ah, I concluded the same thing, yet was really implying that some interaction between the card and the logic board was more the source. I had talked myself out of the only logical conclusion since the button board (front panel card) seemed too straightforward in its construction (three tested normal resistors, 6 PC mount dimple switches which seem to function normally and a normally functioning LED). I suppose I'm a bit jaded by my prior experiences with logic boards!

                        Thanks for pulling the manual...I had looked, but overlooked it on that site.

                        Al, I merely disconnected the button board from the front and am staring at it right now with the ribbon hanging limp and the pesky button board next to it. I just plugged it back in (while hot) and the dancing menu returns! The power LED is steady green (I can hear it laughing at me in binary).

                        Now, it's taunting me by working normally! Oh wait, no, it's dancing again!

                        Ugh.

                        The button board only has 10 components, and all appear to test fine. I suppose I could place a small ceramic across the leads in a poor man's de-bouncer style.....

                        Comment


                          #13
                          Re: Samsung 731N menu keeps popping up

                          Originally posted by PlainBill View Post
                          Compare the voltages at pins 2 and 3 of CN200 PlainBill
                          Which point to use the reference while measuring pins 2 and 3?

                          Now, it won't dance at all....I think it fears the combined forces of Badcaps veterans!

                          Comment


                            #14
                            Re: Samsung 731N menu keeps popping up

                            Originally posted by romansroad View Post
                            Which point to use the reference while measuring pins 2 and 3?

                            Now, it won't dance at all....I think it fears the combined forces of Badcaps veterans!
                            Ground - CN200, pin 4. Take a look at the schematic. Pins 2 and 3 are pulled high by resistors. The front panel board schematic isn't shown, but the various buttons pull the lines low through resistors. While you have measured the obvious components, you missed a couple. The PC board itself, and the connector.

                            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


                              #15
                              Re: Samsung 731N menu keeps popping up

                              I noted the board itself wasn't on the schematic and saw the pull down resistors. You're right, as I didn't suspect the board, and remain suspicious of the cable/connectors. I'll check that voltage and report back. I considered squentially removing the switches, and testing the board, but lately the defect has been more sporadic (I hate intermittant defects). Thanks to all, and I look forward to finding the source.

                              Comment


                                #16
                                Re: Samsung 731N menu keeps popping up

                                I measured the voltage at the panel board end, i.e. not at the logic board to avoid opening it up again. On my unit, CN901 is the connector on the panel board. With the board plugged in, pin 2, 3, 4 all read 1.3v. With the panel board disconnected (at the panel end of the ribbon cable) pins 2 and 3 read0.03 v

                                Comment


                                  #17
                                  Re: Samsung 731N menu keeps popping up

                                  Originally posted by romansroad View Post
                                  I measured the voltage at the panel board end, i.e. not at the logic board to avoid opening it up again. On my unit, CN901 is the connector on the panel board. With the board plugged in, pin 2, 3, 4 all read 1.3v. With the panel board disconnected (at the panel end of the ribbon cable) pins 2 and 3 read0.03 v
                                  That seems to be a problem. Pin 4 should read 0 volts. Pins 2 & # should read 1.8 volts.

                                  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

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