Samsung UN65MU8000FXZA Dead NO power NO standby light won't turn on

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  • rgla
    Member
    • Nov 2021
    • 23
    • United States

    #1

    Samsung UN65MU8000FXZA Dead NO power NO standby light won't turn on

    Hi. First time post. I've scoured the previous forums looking for info - there isn't much for my model
    UN65MU8000FXZA

    We had a power outage. Everything plugged into the Monster surge protector seems to be fine except my Samsung TV. It was dead when the power came back to the house.

    Here's what I've looked at:
    Unplugged main board from power supply - BACKLIGHTS COME ON.

    Ordered new main board - still didn't work. Not sure if used MB was DOA

    MAIN BOARD = BN94-12295K
    PSB= BN44-00912 L65E8NR_MHS

    There doesn't seem to be a pin for Standby like on other boards
    The value on pin 16. power on/off seems high but what do I know.

    Please help me diagnose - is the power supply board done?

    Here are the values I tested for VOLTS. I didn't have the needle tips for multimeter so made my own but here are the values
    WITH = with MB connected
    WO = without MB connected

    CNM803 WITH WO
    1. GND 0 0
    2. GND 0 0
    3. GND 0 0
    4. GND 0 0
    5. VAMP 9 12.85
    6. GND 0 0
    7. VAMP 9 12.85
    8. OD_LEVL 0 3.2
    9. VAMP 9 12.85
    10 FAIL COUNT 0 13
    11 A13V 9 12.85
    12 OD ON OFF 0 3.2
    13 A13V 9 12.85
    14 BLU 0 3.2
    15 A13V 9 12.5
    16 POWER ON/OFF 96 4.5
    17 A13V 9 12.85
    18 GND 0 0
    19 GND 0 0
    20 GND 0 0
    Last edited by SMDFlea; 12-01-2021, 05:22 AM. Reason: UN65MU8000FXZA
  • dskall
    Badcaps Legend
    • Oct 2016
    • 2905
    • usa

    #2
    Re: Samsung 65 Dead NO power NO standby light won't turn on

    16 POWER ON/OFF 96 4.5? 96vdc?
    I assume no responsibility for any stupid suggestions I might post.

    Comment

    • dick_barton
      Badcaps Legend
      • Aug 2015
      • 6642
      • Wales

      #3
      Re: Samsung 65 Dead NO power NO standby light won't turn on

      Maybe 96mV?
      Willing to help but I'm no expert.

      Comment

      • dskall
        Badcaps Legend
        • Oct 2016
        • 2905
        • usa

        #4
        Re: Samsung 65 Dead NO power NO standby light won't turn on

        What voltages does the old mainboard have? Seems the mainboard is pulling down your 13v line.
        I assume no responsibility for any stupid suggestions I might post.

        Comment

        • rgla
          Member
          • Nov 2021
          • 23
          • United States

          #5
          Re: Samsung 65 Dead NO power NO standby light won't turn on

          Yes the 96 is VDC. I didn't move the Meter to another setting.
          It seemed high to me. This was only when the cable from PB to MB was disconnected. There's actually 2 cables running from PB to MB.

          I got another mainboard today but it was one letter off
          BN94-12295K (original board) BN94-12295J - new board. The backlights started flashing and I think the standby light was flashing. The repair shop said it must be the MB but I'm not convinced. He wasted to solder a part from the J board to my K board and said it would probably work.

          I don't want to buy a new MB and have the PB fry it.
          This did happen after a power outage so maybe it was a one time surge?

          Thanks for the help

          Comment

          • rgla
            Member
            • Nov 2021
            • 23
            • United States

            #6
            Re: Samsung 65 Dead NO power NO standby light won't turn on

            I'm pretty new to this so excuse this question.
            I did find a "pin" in the middle of the power board that says "stndby" 7.5 ON 11
            Not sure what this is called - a pin? it looks almost like a staple that's about an inch long. How do I test this? set meter to VDC, Ground the black meter probe to the body of the TV and touch the red probe to the staple/pin (it's in the middle of the board and doesn't have a cable or anything near it.

            Comment

            • dskall
              Badcaps Legend
              • Oct 2016
              • 2905
              • usa

              #7
              Re: Samsung 65 Dead NO power NO standby light won't turn on

              Need some pictures of connectors and boards.
              I assume no responsibility for any stupid suggestions I might post.

              Comment

              • rgla
                Member
                • Nov 2021
                • 23
                • United States

                #8
                Re: Samsung 65 Dead NO power NO standby light won't turn on

                Here are the images.
                Thanks for the help.
                Attached Files

                Comment

                • dick_barton
                  Badcaps Legend
                  • Aug 2015
                  • 6642
                  • Wales

                  #9
                  Re: Samsung 65 Dead NO power NO standby light won't turn on

                  You can measure the voltage on that link and see if it is at 7.V volts when in standby and 11.8V when out of standby. Meter set to dc voltage and can use the chassis as ground.
                  Willing to help but I'm no expert.

                  Comment

                  • rgla
                    Member
                    • Nov 2021
                    • 23
                    • United States

                    #10
                    Re: Samsung 65 Dead NO power NO standby light won't turn on

                    Thanks for the follow up help. Here are the voltages I got on the standby link (jumper?) (HOT side of board)
                    The TV was not ON. It was just plugged in. It won't turn on so I'm not sure how to assess the info from the board:
                    According to the board it should be 7.5 standby and 11.8 on.

                    With the main board connected the voltage was 9v
                    Withe the main board DISCONNECTED the voltage was 12.85

                    somewhat similar to what I was getting at the cable connection pins.
                    Still not sure if the power on/off connection cable pin is supposed to be 96 and then down to 4.5

                    Comment

                    • dskall
                      Badcaps Legend
                      • Oct 2016
                      • 2905
                      • usa

                      #11
                      Re: Samsung 65 Dead NO power NO standby light won't turn on

                      That does not appear to be hot side. All voltages on that side taken from cold side ground as on pads for screw holes.
                      I assume no responsibility for any stupid suggestions I might post.

                      Comment

                      • vinceroger69
                        Badcaps Legend
                        • Mar 2012
                        • 6714
                        • uk

                        #12
                        Re: Samsung 65 Dead NO power NO standby light won't turn on

                        This maybe worth a read
                        https://masterelectronicsrepair.blog...amsung_98.html

                        Comment

                        • rgla
                          Member
                          • Nov 2021
                          • 23
                          • United States

                          #13
                          Re: Samsung 65 Dead NO power NO standby light won't turn on

                          Sorry. You are correct. This is on the COLD side.
                          I put the black probe in a screw hole on the chassis of the tv.
                          Does any of that matter for the reading?

                          Comment

                          • dskall
                            Badcaps Legend
                            • Oct 2016
                            • 2905
                            • usa

                            #14
                            Re: Samsung 65 Dead NO power NO standby light won't turn on

                            Hot side ground and cold side ground are 2 different things. Your voltage readings are odd. As in 96v doesn't seem valid. Are your batteries good in your voltmeter?
                            I assume no responsibility for any stupid suggestions I might post.

                            Comment

                            • rgla
                              Member
                              • Nov 2021
                              • 23
                              • United States

                              #15
                              Re: Samsung 65 Dead NO power NO standby light won't turn on

                              All the voltage readings I took were on the cold side. I grounded to a screw hole / chassis in the back of the TV.
                              New batteries, new multimeter.

                              It seems like the other readings were fine so I suspect the 96 is a correct reading. As soon as I disconnect the main board it goes down to 4.5

                              Why would the standby jumper pin not measure 7.5 or 11.8?
                              With the main board connected the voltage was 9v
                              Withe the main board DISCONNECTED the voltage was 12.85

                              Comment

                              • dskall
                                Badcaps Legend
                                • Oct 2016
                                • 2905
                                • usa

                                #16
                                Re: Samsung 65 Dead NO power NO standby light won't turn on

                                Are those voltages with old mainboard or new? Are you sure pin 16 was not .96vdc.
                                I assume no responsibility for any stupid suggestions I might post.

                                Comment

                                • rgla
                                  Member
                                  • Nov 2021
                                  • 23
                                  • United States

                                  #17
                                  Re: Samsung 65 Dead NO power NO standby light won't turn on

                                  Old mainboard. I don't have the new one yet. Hard to find and even harder to find someone who wants to look into the problem with the board and fix it.

                                  Comment

                                  • dskall
                                    Badcaps Legend
                                    • Oct 2016
                                    • 2905
                                    • usa

                                    #18
                                    Re: Samsung 65 Dead NO power NO standby light won't turn on

                                    Seems you have a bad mainboard.
                                    I assume no responsibility for any stupid suggestions I might post.

                                    Comment

                                    • vinceroger69
                                      Badcaps Legend
                                      • Mar 2012
                                      • 6714
                                      • uk

                                      #19
                                      Re: Samsung 65 Dead NO power NO standby light won't turn on

                                      Originally posted by rgla
                                      Old mainboard. I don't have the new one yet. Hard to find and even harder to find someone who wants to look into the problem with the board and fix it.
                                      This is the only site i can see who has any in stock not cheap though
                                      https://www.tvpartstoday.com/BN94-12...n94-12295k.htm

                                      Comment

                                      • lotas
                                        Badcaps Legend
                                        • Jan 2016
                                        • 4503
                                        • Russia

                                        #20
                                        Re: Samsung 65 Dead NO power NO standby light won't turn on

                                        Most likely, the firmware of the standby mode IC1604 25Q40 flew off, as always in the "MU" series. Do you have main BN41-02570B?

                                        Comment

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