Need help with Samsung LN40E550f7f

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  • Kindred1
    Senior Member
    • Feb 2018
    • 55
    • USA

    #81
    Re: Need help with Samsung LN40E550f7f

    Bottom line is we do have voltage from main to power board when t.v. is powered on. - Sorry for the confusion.

    Comment

    • nomoresonys
      Badcaps Legend
      • Jan 2013
      • 12086
      • U.S.

      #82
      Re: Need help with Samsung LN40E550f7f

      Looks like the mainboard isn't sending the blu_on signal to the power supply.

      Comment

      • nomoresonys
        Badcaps Legend
        • Jan 2013
        • 12086
        • U.S.

        #83
        Re: Need help with Samsung LN40E550f7f

        You could try fixing the mainboard but it can be very technical.

        Comment

        • Kindred1
          Senior Member
          • Feb 2018
          • 55
          • USA

          #84
          Re: Need help with Samsung LN40E550f7f

          So to clarify on my end. there is no power on Blu_on - during standby. When tv is powered on, then I have voltage. Therefore, the main board is sending signal and the signal is staying on. - So, I think I'm back to checking the inverter board. The layout is different than the ones I find online. I'm going to look again, the post a pic of it if I'm unsuccessful. Unless you all have any other has suggestions.

          Comment

          • nomoresonys
            Badcaps Legend
            • Jan 2013
            • 12086
            • U.S.

            #85
            Re: Need help with Samsung LN40E550f7f

            Originally posted by Kindred1
            Bottom line is we do have voltage from main to power board when t.v. is powered on. - Sorry for the confusion.
            Ok, just to be clear, with all boards hooked up, you do have about 3 volts on blu_on pin, when you check it?

            Comment

            • nomoresonys
              Badcaps Legend
              • Jan 2013
              • 12086
              • U.S.

              #86
              Re: Need help with Samsung LN40E550f7f

              Well if your inverters you have 2, the original and one you bought, check out ok, it may be a backlight issue.

              Comment

              • nomoresonys
                Badcaps Legend
                • Jan 2013
                • 12086
                • U.S.

                #87
                Re: Need help with Samsung LN40E550f7f

                http://www.shopjimmy.com/cmo-27-d070...t-inverter.htm good pic. of the inverter, probably test it next.

                Comment

                • nomoresonys
                  Badcaps Legend
                  • Jan 2013
                  • 12086
                  • U.S.

                  #88
                  Re: Need help with Samsung LN40E550f7f

                  https://www.youtube.com/watch?v=oE6K4xBVweA checking inverter its a samsung but a different model, gives you a good idea of what to do.

                  Comment

                  • freakaftr8
                    Badcaps Legend
                    • Oct 2012
                    • 3743
                    • USA

                    #89
                    Re: Need help with Samsung LN40E550f7f

                    This model does have pull up resistors. Point in case, if you unplug mainboard from power supply you will get backlights. If you don't, look at inverter or CCFLs.

                    Shine a flashlight into the screen and hit the menu button. See anything?

                    These E series were some if the last that used CCFLs before going all LED. They have a moderately high failure rate. The connections that the CCFL bulbs use inside are spring loaded into the sockets. They break down.
                    Last edited by freakaftr8; 02-27-2018, 01:17 AM.
                    Did I leave the soldering iron on?

                    Comment

                    • nomoresonys
                      Badcaps Legend
                      • Jan 2013
                      • 12086
                      • U.S.

                      #90
                      Re: Need help with Samsung LN40E550f7f

                      Was trying to find a video with someone testing an E series inverter but no luck, not sure of the differences between series.
                      Last edited by nomoresonys; 02-27-2018, 05:00 AM.

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #91
                        Re: Need help with Samsung LN40E550f7f

                        This power supply board it supplies high frequency AC to connector CNI801 pin 3 (LOW 193VAC) and pin 1 (HIGH 373VAC) of the power supply board to drive the Primary winding of the Inveter transformers on the Inverter transformer board.
                        If it is bad lamp problem, the backlights should flash on for seconds (unless ALL the lamps are bad which is not likely) before the inverter transformer driver circuit on the power supply board goes into protection shutdown.
                        O.P. need to verify if he is getting the high frequency AC drive Voltage to drive the primary side of the inverter transformer on the inverter transformer board or not.
                        Last edited by budm; 02-27-2018, 10:47 AM.
                        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

                        • Kindred1
                          Senior Member
                          • Feb 2018
                          • 55
                          • USA

                          #92
                          Re: Need help with Samsung LN40E550f7f

                          Originally posted by nomoresonys
                          Ok, just to be clear, with all boards hooked up, you do have about 3 volts on blu_on pin, when you check it?
                          With everything hooked up and the tv powered on I get 5.14v on blu_on.

                          Comment

                          • Kindred1
                            Senior Member
                            • Feb 2018
                            • 55
                            • USA

                            #93
                            Re: Need help with Samsung LN40E550f7f

                            Originally posted by freakaftr8
                            This model does have pull up resistors. Point in case, if you unplug mainboard from power supply you will get backlights. If you don't, look at inverter or CCFLs.

                            Shine a flashlight into the screen and hit the menu button. See anything?

                            These E series were some if the last that used CCFLs before going all LED. They have a moderately high failure rate. The connections that the CCFL bulbs use inside are spring loaded into the sockets. They break down.
                            Yes, I can see the screen static and some lettering with the flashlight. No backlights with mainboard unplugged.

                            Comment

                            • nomoresonys
                              Badcaps Legend
                              • Jan 2013
                              • 12086
                              • U.S.

                              #94
                              Re: Need help with Samsung LN40E550f7f

                              I guess test the inverter, if that's ok, what else could it be but a bad ccfl?

                              Comment

                              • Kindred1
                                Senior Member
                                • Feb 2018
                                • 55
                                • USA

                                #95
                                Re: Need help with Samsung LN40E550f7f

                                Originally posted by budm
                                This power supply board it supplies high frequency AC to connector CNI801 pin 3 (LOW 193VAC) and pin 1 (HIGH 373VAC) of the power supply board to drive the Primary winding of the Inveter transformers on the Inverter transformer board.
                                If it is bad lamp problem, the backlights should flash on for seconds (unless ALL the lamps are bad which is not likely) before the inverter transformer driver circuit on the power supply board goes into protection shutdown.
                                O.P. need to verify if he is getting the high frequency AC drive Voltage to drive the primary side of the inverter transformer on the inverter transformer board or not.

                                I think we found our problem Budm. I am not getting voltage at those pins. I am checking with inverter unplugged direct from the pins on the board.

                                Comment

                                • Kindred1
                                  Senior Member
                                  • Feb 2018
                                  • 55
                                  • USA

                                  #96
                                  Re: Need help with Samsung LN40E550f7f

                                  So, where do I check for the fault?

                                  Comment

                                  • Kindred1
                                    Senior Member
                                    • Feb 2018
                                    • 55
                                    • USA

                                    #97
                                    Re: Need help with Samsung LN40E550f7f

                                    Weird thing is, I remember getting some voltage there early on, tho' I don't remember what they were.

                                    Comment

                                    • nomoresonys
                                      Badcaps Legend
                                      • Jan 2013
                                      • 12086
                                      • U.S.

                                      #98
                                      Re: Need help with Samsung LN40E550f7f

                                      Trying to remember if you had the proper voltage on the filter capacitor legs?

                                      Comment

                                      • Kindred1
                                        Senior Member
                                        • Feb 2018
                                        • 55
                                        • USA

                                        #99
                                        Re: Need help with Samsung LN40E550f7f

                                        That's the large 450v caps?

                                        Comment

                                        • nomoresonys
                                          Badcaps Legend
                                          • Jan 2013
                                          • 12086
                                          • U.S.

                                          #100
                                          Re: Need help with Samsung LN40E550f7f

                                          Yes, remember high voltage in that area use caution.
                                          Last edited by nomoresonys; 02-27-2018, 03:41 PM.

                                          Comment

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