Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

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  • SurrealMustard
    Badcaps Veteran
    • Jan 2015
    • 486
    • The United States of America

    #1

    Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

    Got another stumper for the community. This one is right up there with some of the strangest problems I've ever seen on anything:

    Basically, this Samsung LCD television works fine, but when tuned to the VGA input, it will blank the screen and turn off the backlight and slowly blink the power light until the video source is turned off or the cable is disconnected, at which point the screen will turn back on and display the usual "check connection" message. This has been an issue for years, but we just stopped using the VGA port when it originally cropped up because the issue is not present on any other input. When it originally started, it happened suddenly and abruptly and without explanation or provocation.

    Originally, I thought it was perhaps some kind of settings issue, so I reset the television and even upgraded the firmware (successfully), but the problem on the VGA port still persists. Is there any known fix for this, or are we just going to have to stick with HDMi and component if we don't want to replace the mainboard?
  • sordids999
    Badcaps Legend
    • May 2013
    • 2149
    • uk

    #2
    Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

    Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

    Comment

    • Alastair E
      Chief Womble
      • Mar 2013
      • 1963
      • U.K.

      #3
      Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

      VGA set to too high a resolution for the set..
      TELEFIX

      How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
      http://www.irf.com/technical-info/appnotes/an-1088.pdf
      PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

      Comment

      • dick_barton
        Badcaps Legend
        • Aug 2015
        • 6642
        • Wales

        #4
        Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

        SurrealMustard,
        It would be interesting to know if Alastair E hit your problem smack on the head for future reference
        Thanks
        Willing to help but I'm no expert.

        Comment

        • Alastair E
          Chief Womble
          • Mar 2013
          • 1963
          • U.K.

          #5
          Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

          I ran into this issue with an old Plasma Samsung set--It was a 480p/EDTV set, on anything higher than equiv 720p set would shut down...

          Just a thought...
          TELEFIX

          How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
          http://www.irf.com/technical-info/appnotes/an-1088.pdf
          PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

          Comment

          • SurrealMustard
            Badcaps Veteran
            • Jan 2015
            • 486
            • The United States of America

            #6
            additional details

            Originally posted by sordids999
            Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem
            That's kind of difficult because this one is still on the wall, hooked up, and in circulation. I'll see if I can find any pictures on the web and if not, we will explore the logistics of taking it down to photograph.


            Originally posted by Alastair E
            VGA set to too high a resolution for the set..
            Originally posted by dick_barton
            SurrealMustard,
            It would be interesting to know if Alastair E hit your problem smack on the head for future reference
            Thanks
            Originally posted by Alastair E
            I ran into this issue with an old Plasma Samsung set--It was a 480p/EDTV set, on anything higher than equiv 720p set would shut down...

            Just a thought...
            Negatory. It does this at all supported resolutions. The only way to bypass the problem is to unplug the cable.

            Comment

            • budwich
              Badcaps Legend
              • Jul 2015
              • 3097
              • Canada

              #7
              Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

              Does your problem exist whether your vga cable is tereminated or not... ie. with something / computer plugged in versus just the cable only. What kind of vga cable have you been using.... ie. full 15 pin or an "abreviated" one... note just because there are 15 pins in the connector doesn't mean that all pins are connected.

              Comment

              • SurrealMustard
                Badcaps Veteran
                • Jan 2015
                • 486
                • The United States of America

                #8
                supplementary details

                Originally posted by budwich
                Does your problem exist whether your vga cable is tereminated or not... ie. with something / computer plugged in versus just the cable only.
                You mean connected, but with the computer not outputting video to it? I have not tried that yet, but will do so the next time I get a chance and report back the findings.

                Originally posted by budwich
                What kind of vga cable have you been using.... ie. full 15 pin or an "abreviated" one... note just because there are 15 pins in the connector doesn't mean that all pins are connected.
                Originally (years ago when the problem first cropped up) we were using a VGA extension cable, which I know for a fact did not have any of the data pins connected. I don't think this has much bearing though because it was working fine with that extension one day (and many days before that) and stopped the next. I'll try to track down a "non-abbreviated" cable and see if it makes any difference though.

                Comment

                • budwich
                  Badcaps Legend
                  • Jul 2015
                  • 3097
                  • Canada

                  #9
                  Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                  Of course, you haven't indicated what is on the other end of the vga cable but you have now indicated that it worked and then stopped... hmmm. Did the "other end" change? What devices have you tried?

                  Comment

                  • SurrealMustard
                    Badcaps Veteran
                    • Jan 2015
                    • 486
                    • The United States of America

                    #10
                    interesting VGA finds

                    Originally posted by budwich
                    Of course, you haven't indicated what is on the other end of the vga cable but you have now indicated that it worked and then stopped... hmmm. Did the "other end" change? What devices have you tried?
                    At this point, one standard desktop video card and one laptop.

                    Originally posted by budwich
                    Does your problem exist whether your vga cable is tereminated or not.[?]
                    Got around to testing this again today. Interestingly enough, if a computer is off (but still connected), the television will do the same thing. Very fascinating.

                    Originally posted by budwich
                    What kind of vga cable have you been using[?]
                    Upon testing it with another monitor, I have confirmed that the cable I am using to test is indeed a fully-featured one, so now we know that the issue exists with both types (fully featured or video-only).

                    Comment

                    • budwich
                      Badcaps Legend
                      • Jul 2015
                      • 3097
                      • Canada

                      #11
                      Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                      Not sure what you mean by "full featured"... you determined this by doing a continuity test on the cable?

                      It would appear from the "computer off" test that your issue is indeed more with the TV set / connector than the computer end.... hence the previous question.
                      Last edited by budwich; 03-16-2016, 11:09 AM.

                      Comment

                      • Diah
                        Badcaps Legend
                        • Feb 2013
                        • 6355
                        • Germany

                        #12
                        Re: interesting VGA finds

                        Originally posted by SurrealMustard
                        ..
                        its common fault by this model of Samsung, No picture or turn off at Analog PC signal ..

                        it caused it 2 reasons
                        1- the jack CN1000 the black color on the left side of PC socket input on the main board.

                        2- the Main IC400, failed at switching to Analog PC Signal.

                        no 1 are the most insert sound source in it from PC and try

                        Comment

                        • budwich
                          Badcaps Legend
                          • Jul 2015
                          • 3097
                          • Canada

                          #13
                          Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                          my limited findings with a samsung is that grounds play an important role. I would check the cables being used first before going into the "bowels" of the set especially if you need to demount it.

                          Comment

                          • SurrealMustard
                            Badcaps Veteran
                            • Jan 2015
                            • 486
                            • The United States of America

                            #14
                            response to findings

                            Originally posted by budwich
                            Not sure what you mean by "full featured"... you determined this by doing a continuity test on the cable?
                            By "fully featured", I mean that it has more than just the video pins connected because it does transmit resolution support data from the connected display to the computer, unlike the primitive cables which do not do this.

                            Originally posted by Diah
                            its common fault by this model of Samsung, No picture or turn off at Analog PC signal ..

                            it caused it 2 reasons
                            1- the jack CN1000 the black color on the left side of PC socket input on the main board.

                            2- the Main IC400, failed at switching to Analog PC Signal.

                            no 1 are the most insert sound source in it from PC and try
                            Interesting that you mention it being a common fault. I ran some web searches and found hardly any reference to the issue. Going back to the diagnosis though, which one is the CN1000 jack? And what did you mean by "no 1 are the most insert sound source in it from PC and try"?

                            Originally posted by budwich
                            my limited findings with a samsung is that grounds play an important role. I would check the cables being used first before going into the "bowels" of the set especially if you need to demount it.
                            That's what I was thinking too. Are Samsungs more sensitive to the kind of VGA cable that is used? Or do they become less keen on lower quality cabling over time (as seems to be the case here)? At any rate, I've got a couple other spare cables hanging around, so I'll give them a try when I get a chance next.

                            Comment

                            • Diah
                              Badcaps Legend
                              • Feb 2013
                              • 6355
                              • Germany

                              #15
                              Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                              if you were searching the web on the service manual of yours TV was better than searching on the same mentioned fault..... funny......this fault also described at service manual of this model.

                              any way.. on the left side of pc SOCKET on the TV a audio PC in, use only IN with audio signal and switch tv to pc source. you will know if it gone off or not.

                              tipps, of sure you have never used this pc audio input. suggest to plug the jack first in out for several time then test.

                              Comment

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                                How did we go from ' Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD' to PC audio input? I surely like to see the service manual that describes this fault, it will save us lots of time.
                                Never stop learning
                                Basic LCD TV and Monitor troubleshooting guides.
                                http://www.badcaps.net/forum/showthr...956#post305956

                                Voltage Regulator (LDO) testing:
                                http://www.badcaps.net/forum/showthr...999#post300999

                                Inverter testing using old CFL:
                                http://www.badcaps.net/forum/showthr...er+testing+cfl

                                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                http://s807.photobucket.com/user/budm/library/

                                TV Factory reset codes listing:
                                http://www.badcaps.net/forum/showthread.php?t=24809

                                Comment

                                • budwich
                                  Badcaps Legend
                                  • Jul 2015
                                  • 3097
                                  • Canada

                                  #17
                                  Re: response to findings

                                  Originally posted by SurrealMustard
                                  By "fully featured", I mean that it has more than just the video pins connected because it does transmit resolution support data from the connected display to the computer, unlike the primitive cables which do not do this.

                                  .....



                                  That's what I was thinking too. Are Samsungs more sensitive to the kind of VGA cable that is used? Or do they become less keen on lower quality cabling over time (as seems to be the case here)? At any rate, I've got a couple other spare cables hanging around, so I'll give them a try when I get a chance next.
                                  Like any "complex" comms standards, vga can be implemented is almost any form by a given manufacturer AND the same can be said of the cables... :-)

                                  Like hdmi, various scenarios of vga with cables, equipment, deployment layout can cause lots of headaches.

                                  Changing cables "blindly" may or may not help... you need to actually do some testing of a given cable to ensure you understand what is connecting where paying particular attention to grounding (based on my "experience"). In vga, there are lots... :-)

                                  Comment

                                  • SurrealMustard
                                    Badcaps Veteran
                                    • Jan 2015
                                    • 486
                                    • The United States of America

                                    #18
                                    Samsung VGA

                                    Originally posted by budm
                                    How did we go from ' Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD' to PC audio input? I surely like to see the service manual that describes this fault, it will save us lots of time.
                                    That's what I was thinking too. I think what he may have been getting at was to see if there is still sound when the television turns off the screen during those times when the VGA cable is plugged in.

                                    Originally posted by budwich
                                    Like any "complex" comms standards, vga can be implemented is almost any form by a given manufacturer AND the same can be said of the cables... :-)

                                    Like hdmi, various scenarios of vga with cables, equipment, deployment layout can cause lots of headaches.

                                    Changing cables "blindly" may or may not help... you need to actually do some testing of a given cable to ensure you understand what is connecting where paying particular attention to grounding (based on my "experience"). In vga, there are lots... :-)
                                    So that's a "yes" to my question about the Samsung perhaps getting kind of cranky about the VGA cables that it would like to accept in its old age?

                                    Comment

                                    • budwich
                                      Badcaps Legend
                                      • Jul 2015
                                      • 3097
                                      • Canada

                                      #19
                                      Re: Screen turns off when attempting to use VGA input on Samsung LNT4042HX LCD

                                      not sure you can blame samsung. Cable "characteristics" can change just from plugging and unplugging... either as a result of poor wiring, corrosion, etc... That's why you need to look at the cables to ensure they are doing what they are "designed" for.

                                      Comment

                                      • SurrealMustard
                                        Badcaps Veteran
                                        • Jan 2015
                                        • 486
                                        • The United States of America

                                        #20
                                        So... yes?

                                        Originally posted by budwich
                                        not sure you can blame samsung. Cable "characteristics" can change just from plugging and unplugging... either as a result of poor wiring, corrosion, etc... That's why you need to look at the cables to ensure they are doing what they are "designed" for.
                                        Physical wear probably would not have been an issue because the VGA cable we had in there before had been connected to the same computer for two years completely undisturbed before it abruptly stopped. As for the possibility of corrosion, a mysterious case of it would've had to have come over all our other cables around the same time too because each and every one of them works fine with every other monitor and television that I have access to except for this Samsung.

                                        Comment

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