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    Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

    If someone has the schematic for Samsung BN44-00505A(PD23A0Q) psu, could pls tell me the type for QM853 and QM855 smd transistors? They marked as 2P, but when I google it I found 2 types (MMBT5086 and FMMT2222R) which are different type.

    #2
    Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

    Can you tell us where those two Transistors are in the pictures? I cannot locate those two parts.
    Pictures provided by shopjimmy.
    BTW, what is the board not doing?
    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


      #3
      Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

      Hi, first thx for your respond. These transistors are in the upper right corner at solder side, near the screw hole. The monitor/tv suddenly died. So I open it and when i checked the psu I saw a black spot in the area of PWM IC (STR-W6052S). The IC, the bridge rectifier, a capacitor and the 4A fuse were burn. All the Schottky diodes was ok. After I replace these parts I try the psu but there aren't output voltages. I checked the PWM IC Vcc drop down to 9.6V which means that IC's Bias Assist Function was activated. Then I checked (with multimeter) every active component and I saw that these transistors doesn't seem to work. So I need the part number for these to repalce them.

      Comment


        #4
        Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

        So the A5V (Standby 5V) is not even present?
        The B5V, B13V, VAMP will not appear at the connector until the PS-ON is present.
        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


          #5
          Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

          Yes, not even standby voltage is present.

          Comment


            #6
            Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

            Resistor RM803 (0.2? or 0.3? Ohm) is not damaged? Usually that resistor will go open circuit when the STR shorted out.
            If you monitor the VCC when the power is first appllied, that VCC did go up to 15VDC (startup Voltage generated by the internal charge pump circuit which gets the Voltage from pin1 (D/ST) to charge up the filter cap at the VCC pin till it reaches 15VDC to start the IC then the running Voltage will be generated by the AUX winding of the power transformer.
            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


              #7
              Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

              Hi, sorry for my late reply but I was out of town all the day. Yes I've checked the resistor (it's a 0.3Ω) and it's ok. Also I have test the startup operation of the IC (I've use a variac and I've read ic datasheet) and is normal. Do you have the schematic so you can tell me the type of these transistors?

              Comment


                #8
                Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                I'm troubleshooting one of these too. Phevos, you should say TV model in topic title too, not only PSU type. Mine is a Samsung T22C300EW/EN.

                In my case, 320VDC OK in primary cap, no life in secondary. No Vcc in primary switcher (SanKen STR-W6052S), because it's not switching. Then I detect a slight trace of burst near photocoupler: it's blue ceramic cap [CM804] (221K 1kV) that has blown. Then I notice that primary switcher has pins 3-4 shorted. Strange, no fuse is blown. Nothing else is apparently bad. I'll have to replace STR switcher and cap. Hopefully from scrap.

                [QM853] and [QM855] are SMD in secondary side (near top right at budm picture). I don't think that anything in the secondary has suffered from this primary failure, but your case may be different.
                Last edited by Chungalin; 05-25-2016, 05:50 AM.

                Comment


                  #9
                  Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                  I'm wondering if I can replace a STR-W6052S with a STR-W6252. Same packaging, same pinout, same power capability... I have plenty of the second.
                  Attached Files

                  Comment


                    #10
                    Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                    " No Vcc in primary switcher (SanKen STR-W6052S), because it’s not switching" When power if first applied to the circuit, the VCC pin gets the startup Voltage form the internal charge pump circuit inside the IC, when the VCC pin reaches the startup threshold then the IC will start driving the power transformer primary winding and if everything else is OK then the VCC will be supplied by the AUX winding of the power transformer, at the same time the charge pump circuit will shutdown.
                    So the key point is that the VCC will have top reach startup threshold Voltage first.
                    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


                      #11
                      Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                      Your explanation is more accurate than mine. In this case it's clear to me that switcher is damaged, because same customer has bring another TV (Samsung T24B301EW/EN, with similar PSU BN44-00506A) and it has the same problem (burst ceramic cap [CM804] and dead STR-W6053S, nothing else shorted or open). External surge.

                      I won't try to replace with STR-W6252 or STR-W6253 because of differences in pin 7 function (Brown-In/Out function in STR-W60xx), although it's disabled in this PSU. I'll order right ICs and report result.

                      Comment


                        #12
                        Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                        Hi Chungalin, the tv/monitor model is T22B350ND. Searching for these two transistors
                        in web I found that (probablly) there type is MMBT5086 (it's a Samsung tr.) I'm going to repalce those two transistors with two BC857B (they have the same pin-out and specifications) to see what will happen. Chungalin, do you have the schematic for this psu?
                        Attached Files

                        Comment


                          #13
                          Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                          I have replaced IC STR-W6052S, ceramic cap [CM804] (0.22nF 1000V "221K 1KV") and the TV is working again.

                          Comment


                            #14
                            Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                            hi, any one can tell me the reference for TM801S transformator in that board?
                            I've 350V DC input but nothing in the other side ...

                            Comment


                              #15
                              Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                              Originally posted by joaortnt View Post
                              hi, any one can tell me the reference for TM801S transformator in that board?
                              I've 350V DC input but nothing in the other side ...
                              May I ask why you think the transformer is bad but not the device that drive the primary winding may be bad?
                              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


                                #16
                                Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                                Originally posted by Chungalin View Post
                                I have replaced IC STR-W6052S, ceramic cap [CM804] (0.22nF 1000V "221K 1KV") and the TV is working again.
                                I've got a similar blowout, my kids (who where gaming at the time) tell me it was a spectacular bang with light flash effect and then the inevitable magic smoke.

                                CM804 blowed up, it's a hole in it, probably due to STR-W6052S failing (dead short?), also burning the trace clean off the PCB between resistor RM803 and the heat sink point for STR-W6052S.

                                My question is, how do you get the white gunk off from STR-W6052S and CM804? I tried to get it off using a knife (razor), but it's hard to get clean close to the PCB (top side). Any chemical work for this?

                                Comment


                                  #17
                                  Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                                  Sorry for the double post, doesn't seem like I can edit my previous post, even though it was just a minute after posting it.

                                  I forgot to warn about the the big electrolytic cap CM801S on the board (can't read the specs on it, hidden under gunk, 68uF 500V?), when shorting it out with the screwdriver (old habit) there was a nasty spark, should probably have bled that one out slowly with a resistor instead. Anyway, must be pretty high voltage there.

                                  Comment


                                    #18
                                    Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                                    Originally posted by modrobert View Post
                                    CM804 blowed up, it's a hole in it, probably due to STR-W6052S failing (dead short?)
                                    Let me question the cause-effect order of this apparently recurrent failure. If ceramic capacitor is 1KV rated, and the TV is powered from 230V AC, at that point of the PSU there's nothing that can generate more than 1000V. I'm starting to think that it's the capacitor that fails first. The IC gets shorted because the cap shorts briefly before blowing to bits. What else can make a ceramic capacitor explode this way?

                                    I see no problem in removing the white insulation glue. I use a small flat screwdriver to remove some big chunks and then I unsolder the IC. Once all legs are unsoldered, just pull the IC and all the glue that comes with it.

                                    Comment


                                      #19
                                      Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                                      Originally posted by Chungalin View Post
                                      Let me question the cause-effect order of this apparently recurrent failure. If ceramic capacitor is 1KV rated, and the TV is powered from 230V AC, at that point of the PSU there’s nothing that can generate more than 1000V. I’m starting to think that it’s the capacitor that fails first. The IC gets shorted because the cap shorts briefly before blowing to bits. What else can make a ceramic capacitor explode this way?

                                      I see no problem in removing the white insulation glue. I use a small flat screwdriver to remove some big chunks and then I unsolder the IC. Once all legs are unsoldered, just pull the IC and all the glue that comes with it.
                                      That is because cap is exposed to much higher Voltage than the incoming AC due to the fact that the 230AC is converted to around 330vdc and and if it boost converter that boost the dc to around 400vdc (your board does not have PFC BOOSTER) that is used for the smps which will have back EMF generated by the circuit and needs to be reduced which will can be mush higer that the supplied Voltage. You have to look at the circuit to see how the cap is being used.
                                      cm803 (RCD snubber network), cm804 (in parallel with Source and Drain of the STR IC) are the snubber cap.
                                      Last edited by budm; 11-12-2016, 02:48 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


                                        #20
                                        Re: Samsung BN44-00505A(PD23A0Q) psu, smd transistor types

                                        This PSU is for 22-24" TV-monitors, they don't have PFC, so voltage can never be higher than 320V DC in normal conditions (after rectifying and filtering, with 230V AC input). In 50% cases I've found rectifier bridge shorted too. This would point to input surge instead of cap failure as primary cause. But I have record of other cases where even main fuse was OK!

                                        Comment

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