rca rlded5078a-d

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  • dpcookson
    Member
    • Sep 2015
    • 11
    • Canada

    #21
    Re: rca rlded5078a-d

    Sorry, don't mean to hijack this thread but I am curious if the OP solved their problem as I am experiencing the same issues with an identical board; my voltages to the LEDs read .689v

    Comment

    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8017
      • Canada

      #22
      Re: rca rlded5078a-d

      Not that I know of.
      However after your second or third post, you are able to do your own thread. You can use this one as a guide and report what you find.

      Comment

      • dpcookson
        Member
        • Sep 2015
        • 11
        • Canada

        #23
        Re: rca rlded5078a-d

        Bear with me please, I am by no means an expert here, nor even a seasoned novice, lol.

        Please correct me if i am mistaken,
        After following the board layout according to SJ's pictures I have found that C10F may be the culprit as I have 358 VDC on the "south" side of the (cap?) but only 0.398 VDC on the "north" side.

        Suspect device "C10F" is located below T2F (transformer at top of picture) on "HOT" side of board.

        http://www.shopjimmy.com/proscan-ay1...upply-unit.htm

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #24
          Re: rca rlded5078a-d

          C10F is the DC Blocking/Coupling cap and part of the Half-bridge drive circuit, one one of the cap is connected to the Primary side circuit circuit GND, anothe end is connected to one end of the primary xformer T2F. So one end of the cap will be 0V since it is connected to the primary circuit GND.
          If the cap is bad (need to check its capacitance, common failure of that cap will be the lost of the capacitance) then there will be no output for the LEDs.
          Last edited by budm; 09-13-2015, 08:22 PM.
          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

          • dpcookson
            Member
            • Sep 2015
            • 11
            • Canada

            #25
            Re: rca rlded5078a-d

            22.3 nf

            Seems this cap is right on spec from what I have researched on it. Guess it's back to the drawing board, lol. Thanks for the help, I'm pretty new to this stuff so I appreciate any info I can get.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #26
              Re: rca rlded5078a-d

              There is that 18-pin SMD IC1F that drives the Gate Drive transformer T1F, if you can get the spec sheet to get the pin out to find out if that IC is working or not.
              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

              • dpcookson
                Member
                • Sep 2015
                • 11
                • Canada

                #27
                Re: rca rlded5078a-d

                Okay, thanks for the suggestion. I'll take a look hopefully tomorrow night and see what I can find.

                Comment

                • smuddge
                  Senior Member
                  • Feb 2012
                  • 96
                  • Canada

                  #28
                  Re: rca rlded5078a-d

                  no I haven't solved this yet. was away for a few days. I am looking forward to hearing if SMD IC1F is the problem.

                  Comment

                  • dpcookson
                    Member
                    • Sep 2015
                    • 11
                    • Canada

                    #29
                    Re: rca rlded5078a-d

                    IC1F is a BD9211F

                    I don't honestly know what I'm looking for to test this component so I took some voltage readings with my DMM while the board was wired up and powered on.

                    Pin # = VDC

                    1 = 11.14
                    2 = 4.15
                    3 = 0.001
                    4 = 1.465
                    5 = 0.023
                    6 = 0.020
                    7 = 0.001
                    8 = 0.096
                    9 = 0.001
                    10 = 3.495
                    11 = 0.001
                    12 = 0.001
                    13 = 0.003
                    14 = 0.002
                    15 = 0.025
                    16 = 0.001
                    17 = 0.001
                    18 = 0.001

                    I'm not sure if this is useful, any direction from here is appreciated though, thanks.
                    Last edited by dpcookson; 09-14-2015, 07:24 PM.

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #30
                      Re: rca rlded5078a-d

                      Well, looking at the spec sheet, you do have 11VDC for the VCC pin 1 to run the IC, you also have >2vdc for the STB PIN 2 to turn on the IC.
                      There is not activity at the drive output pin 17, pin 18.
                      I do not understand the definition of the CP PIN 9 CP (timer latch detect voltage), 2vdc is the typical when it latch into shutdown or when it is running.
                      There is no application notes circuit to see how it is used.
                      I need to do more research on this IC, so far it looks like there is no activity from this IC.
                      May be you can monitor pin 9 when TV is OFF and when TV power switch is activated to see if it changes state.
                      Attached Files
                      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

                      • dpcookson
                        Member
                        • Sep 2015
                        • 11
                        • Canada

                        #31
                        Re: rca rlded5078a-d

                        Thank you budm for your time so far. I monitored the voltage on pin 9 while powering the unit on and off a couple times but there was no change.

                        Comment

                        • 2cams70
                          New Member
                          • Sep 2015
                          • 3
                          • Australia

                          #32
                          Re: rca rlded5078a-d

                          Hi Guys,

                          Greetings from Australia. Found an Aldi Bauhn ATV-50FHD3 TV courtesy of the kerbside shopping mall that seems to be a clone of this TV. Has the same issue. Have been right through the AY128D PCB checking MOSFETS replacing IC's (including one mentioned) and no success. I am coming to the conclusion that there is nothing wrong with the power board and that the problem lies with a faulty LED in the display causing the board to go into protection mode - this issue was found by another badcaps member somewhere in relation to another type of TV (search under "badcaps" and the LED driver IC type description). Will be a while until I get a chance to pull the screen apart to check though - any thoughts from you guys?

                          Comment

                          • dpcookson
                            Member
                            • Sep 2015
                            • 11
                            • Canada

                            #33
                            Re: rca rlded5078a-d

                            It just so happens that I already have mine tore down that far, I could test my strips if anyone can point me in the right direction.

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #34
                              Re: rca rlded5078a-d

                              I would expect there will be the output to the LED strop first THEN the fault detection circuit kicks in, so it is either that the meter is too slow to show any Voltage spike at the LED's connector before it drops down to 0V as reported.
                              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

                              • CapLeaker
                                Leaking Member
                                • Dec 2014
                                • 8017
                                • Canada

                                #35
                                Re: rca rlded5078a-d

                                If the problem is indeed a bad LED, I expect the LED driver circuit to come on and ramp up the voltage, then it senses an error, protection circuit kicks in and the voltage goes down. If there is no output at all on the LED driver and BLon is present, there has to be a problem somewhere on the board, or a dead short in the LED wiring. So to rule out the latter part, disconnect the LED's from the PSU and measure again.
                                Last edited by CapLeaker; 09-16-2015, 04:29 AM.

                                Comment

                                • dpcookson
                                  Member
                                  • Sep 2015
                                  • 11
                                  • Canada

                                  #36
                                  Re: rca rlded5078a-d

                                  Okay, measured the LED connector during power cycling and got -394V (why is this negative?) but it dropped out quickly like you guys said it might.

                                  If this is a sign of a bad LED or more how do I check them? I tried setting my DMM to diode to test a few random ones but didn't seem to get anything.
                                  Last edited by dpcookson; 09-16-2015, 07:48 AM.

                                  Comment

                                  • 2cams70
                                    New Member
                                    • Sep 2015
                                    • 3
                                    • Australia

                                    #37
                                    Re: rca rlded5078a-d

                                    Hi dpcookson, would you be able to post a couple of pics of the screen LED's seeing as you have yours already in bits. Does this TV have edge or backlight LED's? Would appreciate it as I haven't dismantled mine that far yet - only gone as far as the PCB's.

                                    Comment

                                    • dpcookson
                                      Member
                                      • Sep 2015
                                      • 11
                                      • Canada

                                      #38
                                      Re: rca rlded5078a-d

                                      It is full backlight, there are 5 strips of 14 LEDs.





                                      note: The TV is "upside-down" in the pics
                                      Attached Files
                                      Last edited by dpcookson; 09-16-2015, 09:01 AM.

                                      Comment

                                      • CapLeaker
                                        Leaking Member
                                        • Dec 2014
                                        • 8017
                                        • Canada

                                        #39
                                        Re: rca rlded5078a-d

                                        Originally posted by dpcookson
                                        Okay, measured the LED connector during power cycling and got -394V (why is this negative?) but it dropped out quickly like you guys said it might.

                                        If this is a sign of a bad LED or more how do I check them? I tried setting my DMM to diode to test a few random ones but didn't seem to get anything.
                                        That depends on where you had your GND lead from your DMM connected to during the measurement.
                                        You can check every diode with your DMM set in diode mode and look for an open or dead short.
                                        Last edited by CapLeaker; 09-16-2015, 10:03 AM.

                                        Comment

                                        • dpcookson
                                          Member
                                          • Sep 2015
                                          • 11
                                          • Canada

                                          #40
                                          Re: rca rlded5078a-d

                                          GND lead of the DMM was on the GND circuit of the board. On power up, the voltage at the LED connector started at +0.69V then about 3-4 seconds later it "dropped" to -394V, then returned to +0.69V. With the unit powered off there is 0V at the LED connector. I suppose it doesn't matter which side of the LED circuit is positive or negative, as long as the LEDs polarity matches.

                                          I realize that an LED is a diode but maybe I was checking them wrong with my meter, if you look at my previous posted pictures, I was connecting my leads to each copper "dot" on both sides of an LED. I tried reversing the leads but came up with an open circuit on the few random LEDs I tested, makes me think I am doing something wrong, that or every LED is "NFG".

                                          Comment

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