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Samsung BN44-00289B Power Board troubleshooting

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    Samsung BN44-00289B Power Board troubleshooting

    Samsung LCD
    LN32B360C5DXZA ver.SG05
    BN44-00289B Power Board

    I get No standby light on tv, and backlight does Not come on with logic board term CN802 disconnected. Im get voltage readings but None at all on CN802 terminal pins.

    My component level knowledge is basic, so this will be a lession for me. I id the transistor pins G D S from schematic but got diff readings reversing polarity, idk which polarity is relavant so i took both directions.

    Any advice on which direction i should research into first based on the symptom issues is appreciated, i don't know where to start. I also included a closeup img on part of the pcb, idk if what im seeing is just part of a coating on the boatd or liquid damage? Would like your opionion as i have no knowledge reference.

    Fuses are ok 0.3 ohm

    Resistance reading with Fuse FM802S removed suggested in this thread. Tho my symptom is different i checked anyway but dont know what its supposed to read.
    Samsung LN32B360 No Power....Diodes ok
    Fuse > P-GND - /
    P-GND > Fuse - 550 ohm

    Voltages
    CN802 Terminal, All pins read 0 vdc

    S-GND > P-GND - 60 vdc

    Cap CP815 - 167 vdc

    Cap CM808 - 13.5 vdc

    ICE UM801S pins - vdc
    1 - 0
    2 - 4.8
    3 - 0
    4 - 166
    5 - 166
    6 - 0
    7 - 13.5
    8 - 0

    Transistors
    QP802S
    + - ohms
    D S /
    S D 470
    G S /
    G D /
    S G 530
    D G /

    QI820 mimics QI821
    + - ohms
    D S /
    S D 420
    G S 675
    G D 1460
    S G 690
    D G /

    Diodes ohm - reverse
    DM801 490 - /
    DM802 560 - /
    DM803 580 - /
    DM852 460 - /

    Zeners ohm - reverse
    ZD801 685 - /
    ZD803 730 - /
    ZD804 300 - 710
    ZD804 725 - / (note R climbed tho like a cap)

    Resistors spec - read
    RM869 0.5 - 0.7
    RM811 39K - 39K
    Attached Files

    #2
    Re: Samsung BN44-00289B Power Board troubleshooting

    UM801s is the standby ic, It needs to operate before anything else, Have you checked or replaced CM804 and Cm808?
    If that ic is working it should give you around +6v on CM852. You need the +5.3v standby voltage before you can turn on the rest of the power supply and pfc circuit.
    You also need to check DM851 and DM857

    Comment


      #3
      Re: Samsung BN44-00289B Power Board troubleshooting

      Thanks, and no i didn't replace anything yet. I don't know where or what to order yet, but notice caps and diodes are cheap so not sure if i should just replace them all? cause shipping may cost more than the parts? I dont usually do this so i dont have spare parts, and i dont have experience to know the likelyhood if caps or diodes would fix the symptom.

      Recommendations on where to order from also since im not ordering large bulks is also appreciated.

      should give you around +6v on CM852
      CM852 had no exposed pins on top so i used center Pin of DM851 to > S-GND which read 0.0v , everything on the cold side read 0.0v

      I only have a multimeter to check the caps, all there resistance climbs to infinit some quicker than others, except CB804 stops at 600 ohm , but does that mean anything cause they're in circuit?

      CP815 - 166 V
      CM808 - 13.5 V
      CM804 - 50mV and continues to drop
      CB804 - 19mV

      DM851
      pins - ohms
      1 , 3 = 0
      1 , 2 = 236
      3 , 2 = 236
      2 , 1 = /
      2 , 3 = /

      DM857
      pins - ohms
      1 , 3 = 0
      1 , 2 = 275
      3 , 2 = 275
      2 , 1 = /
      2 , 3 = /

      Comment


        #4
        Re: Samsung BN44-00289B Power Board troubleshooting

        CM808 - 13.5 V
        CM804 - 50mV and continues to drop
        The 13.5v is the VCC on UM801s, this is created by the internal startup cell. The reason CM804 has no voltage is because: either the ic is not operating due to being defective, or the feed back/run voltage is missing, so check RM890, dm802 and check that the transformer winding between pins 5 & 6 is not open, it should read less than 1Ω

        NOrmally the ic's drain pin will pulse the primary of the transformer, this will induce a voltage in the secondary windings, this induced voltage in winding (pin5) will be rectified by DM802 and charge CM804 to about 27 volts, this voltage is applied through DM803,RM805 and will charge CM808 to about 24v of VCC to turn UB802 on fully
        Last edited by R_J; 09-21-2019, 10:40 PM.

        Comment


          #5
          Re: Samsung BN44-00289B Power Board troubleshooting

          Read this thread.
          https://www.badcaps.net/forum/showth...e32b350&page=3

          Comment


            #6
            Re: Samsung BN44-00289B Power Board troubleshooting

            Originally posted by R_J View Post
            check RM890, dm802 and check that the transformer winding between pins 5 & 6 is not open, it should read less than 1Ω
            Thanks,

            Transformer TM801S
            pins 5 , 6 = 0.3 ohm

            RM890 spec 3 ohm / read 3.5 ohm

            DM802 forward 560 ohm / backward O/L
            Originally posted by tvtimmy View Post
            Thanks, it says he found 3 bad diodes that solved his issue...
            (zd804, dm852, zm804)

            Do my specs look suspect? I dont know how he tested them, im just using a mutimeter ohms diode setting.. and keep in mined my components are still in circuit, i need to acquire a soldering iron.

            Im not qualifed to say, but id guess the only suspect readings i have are ZD804 and ZM804 , but i have no experience to know if some diodes act like that if still in circuit?

            Is it even worth looking at those 2 diodes yet? I think R_J is working through the circuit to check things first and not make guesses, appreciated.

            If they should, recommendations on where to order parts from, cause if they're cheap i may as well replace all the diodes at same time right? Caps too if that would be a good idea.

            Diodes ohm - reverse
            DM801 490 - /
            DM802 560 - /
            DM803 580 - /
            DM852 460 - /

            Zeners ohm - reverse
            ZM801 685 - /
            ZD803 730 - /
            ZD804 300 - 710
            ZM804 725 - / (note R climbed tho like a cap)

            (Fixed ZD > ZM typo post 1)

            Comment


              #7
              Re: Samsung BN44-00289B Power Board troubleshooting

              ZM804 won't be the problem, it is in series with a 1.5K so even if it was bad it would not kill the standby.
              ZD804 would also not kill the standby from working, I would check the resistance of UM801S, pin1 to ground, just to make sure CM802 is'nt shorted.

              It could be that UM801S is bad, You would need a scope to check if it is outputing any pulses.
              It's not a very complicated circuit and only a few components are required for it to work.
              Last edited by R_J; 09-22-2019, 01:37 PM.

              Comment


                #8
                Re: Samsung BN44-00289B Power Board troubleshooting

                Originally posted by R_J View Post
                I would check the resistance of UM801S, pin1 to ground, to make sure CM802 is'nt shorted.

                It could be that UM801S is bad.
                UM801S
                pin1 > P-GND = O/L
                P-GND > pin1 = 600 ohm | 740 ohm on diode setting

                Thank u guys i have a starting point.

                Comment


                  #9
                  Re: Samsung BN44-00289B Power Board troubleshooting

                  Good day.

                  New here and having some trouble with my LCD TV

                  Summary: The TV is not switching ON but the red light is blinking

                  Brand: Samsung

                  Model: LN32B360C5DXZA

                  Power Board: BN44 00289B

                  From google, I was able to get the wiring diagram and a suggestion that the blinking Light is a Power Board Issue.

                  I have opened up the television and disconnected the power board. These are the readings I am getting.

                  Harness CN802
                  PINS ------ MEASURED VALUES
                  PWR ON/OFF ----- 0.783V
                  STBY5.3V ------ 5.3V
                  GND ------ GND
                  13V ------ 12.88V
                  GND ------- GND
                  GND ------ GND
                  5.3V ----- 5.3V
                  5.3V ------ 5.3V
                  GND ------ GND
                  13V ------ 12.88V
                  13V ------ 12.88V
                  INVERTER ON/OFF ------ 2.89V
                  E-PWM ------ 4.95V
                  DET_5V ------- 0V
                  SYNC ------ 0V

                  GND ------ GND

                  Looking at the board I am seeing some burn marks but no swollen caps.
                  Using my multimeter, I got a few CAPS reading "OL"

                  The Largest CAP CP815 measured a voltage of 378Vdc when plugged in.

                  The CAPS showing "OL" (These have no visual swelling)
                  CM876
                  CM867
                  C1801
                  CB804

                  Also I got a Zener diode
                  ZM804 giving continuity.

                  I saw some burn marks around UM801S
                  UM801S - Getting continuity between GND and CS(Current Sense) Pin

                  My question is why is the DET_5V reading 0V? Is the 12.88V sufficient or too low? Could these issues identified be the problem?

                  Any help will be appreciated.
                  Attached Files

                  Comment


                    #10
                    Re: Samsung BN44-00289B Power Board troubleshooting

                    Recapping all the powerboard electrolytics in a tv this old is never a bad idea, be CAREFUL with the big ones, they can hold a DEADLY charge, DigiKey isn't too bad if you get all that you need in one stop, it's when trying to buy just one little component that you hate to pay the shipping fees.

                    Comment


                      #11
                      Re: Samsung BN44-00289B Power Board troubleshooting

                      To get a true reading on any suspect diodes you will need to take it out of circuit.

                      Comment


                        #12
                        Re: Samsung BN44-00289B Power Board troubleshooting

                        12.88v is fine, you don't have DET_5V likely due to a fault in the inverter section, (ie bad transformer) or even a bad ccfl in the panel. UI801 pin 17 is FAIL output that is turning on QI807, connecting the collector to ground.

                        Each transformer has two secondary windings, Check and compare the resistance of each winding, Should be around 1KΩ. Also check for poor solder connections on QI820 & QI821
                        I saw some burn marks around UM801S
                        UM801S - Getting continuity between GND and CS(Current Sense) Pin
                        This is the PFC ic and based on "CP815 measured a voltage of 378Vdc" it is working, The CS pin has RP820 (0.12Ω) to hot ground.
                        Last edited by R_J; 03-05-2021, 07:58 PM.

                        Comment


                          #13
                          Re: Samsung BN44-00289B Power Board troubleshooting

                          Originally posted by R_J View Post
                          12.88v is fine, you don't have DET_5V likely due to a fault in the inverter section, (ie bad transformer) or even a bad ccfl in the panel. UI801 pin 17 is FAIL output that is turning on QI807, connecting the collector to ground.

                          Each transformer has two secondary windings, Check and compare the resistance of each winding, Should be around 1KΩ. Also check for poor solder connections on QI820 & QI821
                          This is the PFC ic and based on "CP815 measured a voltage of 378Vdc" it is working, The CS pin has RP820 (0.12Ω) to hot ground.
                          Thanks for the response. So I did some more troubleshooting today. The QI820 & QI821 are good.

                          However, I am not getting any output on the DT801S. I am getting a 12V to ground on each incoming line to the transformer. So maybe this could be the issue that is causing the no DET5V?

                          Do you by chance know where I can source a transformer like this.

                          The output coils on the transformer are reading 2Ohms.
                          Attached Files

                          Comment


                            #14
                            Re: Samsung BN44-00289B Power Board troubleshooting

                            The fault is not the transformer. Transformers operate with AC not DC, To check the output of the transformer you need a scope. That transformer is just the drive for QI820/821. You need to check the secondaries of TI801S and TI802S

                            Comment


                              #15
                              Re: Samsung BN44-00289B Power Board troubleshooting

                              Ah Ok. Understand. I replaced the suspect components today and checked through the secondary's of that circuit but nothing showing out of the ordinary. Still having same issue.

                              However I came across the PFC line from after the second fuse reads 380Vdc but when it passes over the BD901 , the voltage drops out to 2Vdc. Any idea what can be causing this?

                              Comment


                                #16
                                Re: Samsung BN44-00289B Power Board troubleshooting

                                Well BD901 is open. On some other samsung power supplies they use a .1Ω resistor or a fuse in this position, this acts like a fuse when QI820 & QI821 short.
                                I have no idea what "suspect components" you replaced, so it must be other components that are bad
                                Last edited by R_J; 03-07-2021, 07:03 PM.

                                Comment


                                  #17
                                  Re: Samsung BN44-00289B Power Board troubleshooting

                                  Ok well I am not seeing any markings on the BD901, just looks like a diode.

                                  Should I replace with .1Ohm resistor?

                                  The suspect components I replaced were the capacitors that were reading OL.

                                  CM876
                                  CM867
                                  C1801
                                  CB804

                                  Comment


                                    #18
                                    Re: Samsung BN44-00289B Power Board troubleshooting

                                    I looked at a picture of the board and BD901 should be basically just a wire with a ferrite bead over it, Check if it is indeed open.
                                    Capacitors reading OL with what? ohm meter? You can't check a capacitor like that, you need a capacitor checker or an esr meter.
                                    Last edited by R_J; 03-07-2021, 06:53 PM.

                                    Comment


                                      #19
                                      Re: Samsung BN44-00289B Power Board troubleshooting

                                      Used a multimeter with a function to read the capacitance of a capacitor.

                                      Other capacitors were reading properly when checked.

                                      I removed the BD901 and not getting any resistance on it. What is the function of this component by chance?

                                      TV was working fine and one power surge and I am trying to recover it.

                                      Comment


                                        #20
                                        Re: Samsung BN44-00289B Power Board troubleshooting

                                        BD901 is basically an inductor, I don't think I have ever seen one of these go open. Replace it with a 1Ω 1/2w or maybe a 2~3 amp fuse for testing

                                        Comment

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