(SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • JDC
    Badcaps Veteran
    • May 2015
    • 273
    • USA

    #1

    (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

    ONN 100012588
    Issue: No Power, Then Rebooting After Main Board Change

    Short answer: replace main board and power board
    Technical answer: replace main board and Q306 & Q307 on power board.

    Long answer:

    TV wouldn't turn on. Power switch was fine which means the main board isn't processing the power on signal. Replaced main board. TV turns on now but randomly reboots. Bad main board? EEPROM? Tried to pull main board and got a shock touching the corner of the board. That's weird. C334 (450V 10uf) capacitor is still holding a high charge. That's not right. Took my time discharging it and the rest of the board. C334 had good ESR, so why isn't the board discharging the voltage itself? Poked around, poked around, found that Q306 and Q307 are blown (MBRB20100CT DIODE SCHOTTKY 100V 20A) were blown. Weird again. TV turns on, shows a picture, but the power board is still bad? First for me.

    Replaced power board and all is well now. When benching the TV, do NOT connect to the network as it will not allow you use it as a regular tv afterwards unless you register it.
  • JDC
    Badcaps Veteran
    • May 2015
    • 273
    • USA

    #2
    Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

    that should read "Tried to pull POWER board and got a shock touching"

    Comment

    • nomoresonys
      Badcaps Legend
      • Jan 2013
      • 12096
      • U.S.

      #3
      Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

      Be very careful where you touch it, it can be DEADLY, so where did you touch it that it shocked you? Always be mindful where you are touching with your hands, I only touch the edges of the board with my hands, to try to eliminate shock and possible static electricity messing something up.
      Last edited by nomoresonys; 07-17-2022, 07:44 AM.

      Comment

      • nomoresonys
        Badcaps Legend
        • Jan 2013
        • 12096
        • U.S.

        #4
        Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

        capacitor discharging with resistor, can be done with capacitor in circuit as well: https://www.youtube.com/watch?v=2TcVZ2opuNc

        Comment

        • nomoresonys
          Badcaps Legend
          • Jan 2013
          • 12096
          • U.S.

          #5
          Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

          a little more on it, capacitors can hold a charge for 24 hours without power applied, if they have resistors across them in circuit they will discharge very quickly tho, can test them with multimeter set to vdc to see voltage they are at, best to test them to make sure or just discharge them with resistor: https://www.youtube.com/watch?v=mftW52E6_fk
          Last edited by nomoresonys; 07-17-2022, 07:47 AM.

          Comment

          • JDC
            Badcaps Veteran
            • May 2015
            • 273
            • USA

            #6
            Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

            Originally posted by nomoresonys
            a little more on it, capacitors can hold a charge for 24 hours without power applied, if they have resistors across them in circuit they will discharge very quickly tho, can test them with multimeter set to vdc to see voltage they are at, best to test them to make sure or just discharge them with resistor: https://www.youtube.com/watch?v=mftW52E6_fk
            Yes, you are correct on all 3 posts. I practice discharging the main filter capacitor or at least check for an errant voltage upon powerdown. What surprised me was the 450v corner capacitor on the power board still had a charge. Strangely enough had I not received the shock, I probably wouldn't have figured out anything was wrong because like I said the TV turned on.

            In the 10 years I've been repairing TVs, I've never had one turn on and yet there's an issue with the power board.

            Comment

            • nomoresonys
              Badcaps Legend
              • Jan 2013
              • 12096
              • U.S.

              #7
              Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

              yes that is strange, usually don't get much showing up with bad powerboard.

              Comment

              • fuxxy
                Badcaps Veteran
                • Jan 2013
                • 318
                • USA

                #8
                Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

                Can you elaborate a bit more on the process that led to conclusion of q306 and q307 being blown?

                I am currently working on a similar TV - ONN 65 inch that originally wouldn't show picture - replaced all backlight strips and now all backlight LEDs are lighting uniformly and read the same voltage on my backlight tester. Now I get a single flash from the backlight when pressing the power button.

                This TV also shocked the hell out of me when attempting to disconnect the backlights from the PSU. It's very consistent that each time a power attempt has been made, the backlight connector has plenty of voltage even hours after being unplugged.

                My PSU - https://imgur.com/a/zG61ERH

                Comment

                • fuxxy
                  Badcaps Veteran
                  • Jan 2013
                  • 318
                  • USA

                  #9
                  Re: (SOLVED) - ONN 100012588 No Power, Then Rebooting After Main Board Change

                  Sorry, I guess I couldnt be bothered to read the datasheet.

                  Q306 & Q307 are schottkey barrier diodes. They are tested just like any other diode - They will conduct in one polarity, and insulate in the opposite polarity.
                  The only caveat for the MBRB20100CT is that there are 2 diodes in one package. Since the board is designed so the anodes are connected, the whole package functions as a single diode. The package would need to be removed from the board to test each diode in the package separately.

                  Comment

                  Related Topics

                  Collapse

                  • Dani_2024
                    Sceptre U550CV-UMR 4K LED, Bad Caps on Main Power Board?
                    by Dani_2024
                    Hi and thanks in advance for any input you might provide!
                    I have a Sceptre U550CV-UMRD8POTV83BB 4K LED (this is a dumb tv) that I bought new in August 2021, so It's just completed 3 years.
                    Main power board model: TP.MS3683.PC821 T-Con board: N4TP546UHDPU2L_BO

                    Last Sunday I was watching a dvd and fell asleep for about half hour, when I awoke the tv screen was black and couldn't get the dvd menu to show, so I changed the input to antenna and had sound but no picture, turned it off. I then got online and found this great site! ....read many troubleshooting tips and this...
                    10-28-2024, 05:06 PM
                  • jb_Bak
                    Sony xbr-65x900c main board issues?
                    by jb_Bak
                    Hey guys great forum glad to have found it. I bought a Sony XBR 65X900C cheaply because it didn't work. No signs of life at all not even a light/led. All I hear is a brief high voltage sound when I throw the power to it.

                    Didn't see any obvious signs of damage so right away started checking voltages. This is what I see:
                    Power Board Connector that goes to Main board
                    CN6401
                    Pin 01 NC
                    Pin 02 NC
                    Pin 03 "BL_ON": 0V
                    Pin 04 "N/C"
                    Pin 05 "STBY 3.3V": 3.5V
                    Pin 06 "GND": N/C
                    Pin 07 "AC_OFF"...
                    09-27-2021, 04:52 PM
                  • m1ch43lzm
                    HP Pavilion 15-eh Board DAG7HAMB8F0 - CPU throttling to 0.4GHz (PROCHOT_EXT) and black screen
                    by m1ch43lzm
                    Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
                    Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic...
                    05-12-2025, 08:37 PM
                  • cheeky2
                    Is it possible to upgrade from a Vestel 17MB97 main board to a 17MB110 Main board?
                    by cheeky2
                    I suppose the real question is whether the existing pinouts from ether a 17IPS71 psu are cross compatible with a 17IPS12 psu? If they are then the exchange of the main boards should have no issues providing the screen is compatible with both main boards. Obviously you can change the screen configurations easily enough (providing you have the correct files) for the main board. Why may you ask would I do this? Well a lot of the smart features are no longer working on a Hitachi 48HBT62U main board I wish to give it a new lease of life!
                    Obviously the same LVDS connector for the screen connection...
                    05-25-2024, 03:27 AM
                  • advant
                    Driving a Sharp TCON/panel with a universal main board
                    by advant
                    This thread is about trying to get an Universal Main Board to work with a Sharp TCON and panel.

                    I have a Sharp LC-46D85UN TV that has had a main board issue. Since this model is from 2009, I am not able to find an exact replacement of the main board. Instead, I decided to see if I can future proof this tv by getting a Universal Main Board (T53U21.2) from China to work with the Sharp TCON (CPWBX4291TPZA) and panel. The universal main board supports a 8 bit dual channel LVDS interface whereas the TCON requires a 10 bit dual channel LVDS input. I have modded the LVDS connector to match...
                    02-03-2020, 12:25 AM
                  • Loading...
                  • No more items.
                  Working...