A2991 Logic Board issue, 20volts 0 amps help!

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Stephen
    Meow Meow MEOW!
    • Apr 2020
    • 673
    • United States

    #1

    A2991 Logic Board issue, 20volts 0 amps help!

    Customer plugged in samsung monitor into the board and used it as a power supply, killed UG800 and UG400. I replaced those two with an exact donor board we had In stock and working, board pulls 5volts and then gets like 2.89 amps on the left side. The singular port is the port that failed. Used a perfectly working chips from donor (board was locked) Now I only get 5volts 0 amps on that power and then 20volts 0 amps on the two left side ports, I checked for DFU and nope nothing, computer not turning on. No shorts present anymore. I am confused as I used the exact components from an identical working board. So I am now stuck tracing the issue. I am only getting 12volts at PPBUS_AON . PP3v3 is present and P1v8 is present but nothing. I also put it into the battery and nothing. So I'm lost now. Very confused where I am missing as there are no present shorts here. Am I missing something?
    sigpic
    MEOWING IN THE IMPOSSIBLE UNIVERSE!
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14450
    • Canada

    #2
    PPBUS_AON is dialed up / down over SMBUS. Confirm the voltage to ground on the SMBUS lines used by this regulator. Also suggest to measure the voltage to ground of the SMBUS lines used by the battery BMS.

    Comment

    • Stephen
      Meow Meow MEOW!
      • Apr 2020
      • 673
      • United States

      #3
      Well battery is holding a charge, I tested the lines by itself and the battery is presently sending voltage down the lines. But I will get back with measurements
      sigpic
      MEOWING IN THE IMPOSSIBLE UNIVERSE!

      Comment

      • Stephen
        Meow Meow MEOW!
        • Apr 2020
        • 673
        • United States

        #4
        Are we talking the SDA and SCL lines? Because those measured nothing when plugged into that port. I measured them at .45volts SDA and SCL is 0volts. I am missing 3.3 volts for sure.
        sigpic
        MEOWING IN THE IMPOSSIBLE UNIVERSE!

        Comment

        • mon2
          Badcaps Legend
          • Dec 2019
          • 14450
          • Canada

          #5
          Something could be wrong here. Remove all power. Meter in resistance mode. Measure the resistance to ground on each of these SCL / SDA lines. The TVS ESD diode may have triggered. Have not checked the schematic but for a while, the boards contain a small TVS ESD diode on the battery connector.

          Comment

          • Stephen
            Meow Meow MEOW!
            • Apr 2020
            • 673
            • United States

            #6
            SDA and SCL 1 M ohms on both lines.
            sigpic
            MEOWING IN THE IMPOSSIBLE UNIVERSE!

            Comment

            • Stephen
              Meow Meow MEOW!
              • Apr 2020
              • 673
              • United States

              #7
              Any thoughts?
              sigpic
              MEOWING IN THE IMPOSSIBLE UNIVERSE!

              Comment

              • mon2
                Badcaps Legend
                • Dec 2019
                • 14450
                • Canada

                #8
                Would you have the timing diagram for the power sequencing for this motherboard?

                See attached. Can zoom in on any area of interest on this drawing.

                Click image for larger version  Name:	A2991_power_sequence1.png Views:	0 Size:	525.0 KB ID:	3723114

                Click image for larger version  Name:	A2991_power_sequence2.png Views:	0 Size:	402.6 KB ID:	3723115
                Last edited by mon2; Today, 10:33 AM.

                Comment

                Related Topics

                Collapse

                • Stephen
                  A2991 logic board issue, 20volts 0 amps help!
                  by Stephen
                  Customer plugged in samsung monitor into the board and used it as a power supply, killed UG800 and UG400. I replaced those two with an exact donor board we had In stock and working, board pulls 5volts and then gets like 2.89 amps on the left side. The singular port is the port that failed. Used a perfectly working chips from donor (board was locked) Now I only get 5volts 0 amps on that power and then 20volts 0 amps on the two left side ports, I checked for DFU and nope nothing, computer not turning on. No shorts present anymore. I am confused as I used the exact components from an identical...
                  Yesterday, 03:15 PM
                • Tynan Dill
                  Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?
                  by Tynan Dill
                  I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.

                  Upon bringing it home and plugging it up, it showed a standby light.

                  I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.

                  The screen seems to blackout and stay black, but with a flashlight I can see the display.

                  With my Playstation 4 connected via HDMI, and running a game I can hear sound.

                  Assuming...
                  11-22-2024, 01:46 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
                • ohren
                  Upgrading a Samsung ue55nu7096u with logic board from an ue55ru7105k -- good idea?
                  by ohren
                  I hope this is the right forum to post in despite not technically being a repair, but still a question of swapping boards.

                  I thought I'd explore the possibility to upgrade an existing working Samsung ue55nu7096u with the logic board (and power board if needed) of a newer model (ue55ru7105k) of the same size and appearance (and resolution). The reason being I'd like the extra inputs of that board including component in, an extra HDMI port and bluetooth. Its panel is broken so I have no use for the board otherwise.

                  The models launched in 2018 and 2019 respectively....
                  09-08-2023, 05:24 PM
                • Yanleb
                  LG 60PK550 Logic Control Board EBR63450301
                  by Yanleb
                  Hi all, I just want to share the repair of my 60PK550-UA TV set.

                  The TV set was powering on, just no image. After verification, nothing wrong on the YSus or ZSus boards. Nothing wrong on the main board either.

                  But I noticed that the LED was not flashing on the Logic Control Board. This is an EBR63450301. The LED is supposed to flash even with all the flat cables disconnected, with only the power cable attached.

                  All the voltages measured at the electrolytic capacitors on the board were good. From top left to bottom right:
                  C57: 3.30V
                  C61:...
                  07-20-2023, 12:38 AM
                • Loading...
                • No more items.
                Working...