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    Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

    Hello everyone I was hoping someone might be able to help me identify this IC. Its a Toshiba 50L1350U LCD TV with power supply pk101w0050i. There are numbers on it but they are worn enough I can't read them.

    This set is dead with standby volts and no standby light along with:

    No volts at C601
    questionable MOSFETS Q101 and Q102
    Q502 appears OK
    questionable X2 capacitor CX101 (Carli .33k275V X2 40/110/56, known for failure in coffee makers)

    On the cold side:

    Diode D301 accidentally shorted across pins EL203 and EL204 with power present.
    Voltage of 12.4V present at EL203 after short
    Loss of previously present 12V AUD and 12V_CC voltage of 12.4.
    Resistor R903 appears open.

    Prior to short of EL203 and EL204 the following voltages were present at connector P802

    PWM: 3.1
    BL_ON/off: 0.0 (set will not power on)
    AC_DETECT: 3.1
    5.1V: 5.3V
    12V_LNB: 0
    12V_AUD: 12.4
    12V_CC: 12.4

    So I'm thinking of buying the individual components and soldering them in but just wondering if anyone thinks I missed anything?
    Attached Files
    They call me......."threadkiller"

    #2
    Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

    What is that black ARC flash on one of the bridge rectifier BD101?
    There should be PS-ON pin on one of those connector, I cannot read all the pin names in your pictures, you need to list ALL the pin names so we can see what are missing.
    What is the color code of R903?
    BTW, X/Y caps are not needed for the circuit to function and I doubt they are bad.
    Last edited by budm; 03-29-2018, 09:53 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


      #3
      Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

      Oh... you saw that. I was testing voltage and bridged BD101 to the heat sink. Blew fuse F101, replaced it and voltage was restored. Think I had 165V on the DC side.

      Pins from left to right on P802

      PWM
      5.1
      BL_ON/OFF
      POWER_TV
      AC_DETECT
      5.1V
      GND
      12V_LNB
      GND
      12V_AUD
      GND
      GND
      12V_CC
      12V_CC
      12V_CC

      Resistor: Red, red, yellow, gold. Appears to be 220K, re-tested on proper scale and is 215K
      They call me......."threadkiller"

      Comment


        #4
        Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

        Looks like spam to me
        They call me......."threadkiller"

        Comment


          #5
          Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

          'power_tv' = ps-on.
          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


            #6
            Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

            Bet you need that voltage? I'm pretty sure I remember that being zero. I thought that's what that meant. That to ground will power the set up without the main board?
            Last edited by DXseekerMO; 03-29-2018, 11:15 PM.
            They call me......."threadkiller"

            Comment


              #7
              Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

              >2VDC = main power supply on, I.E. the switched 12VDC and the Voltage to feed the LED driver circuit.
              <1V = OFF.
              Same for the BL-ON.
              BTW, Always report ALL the Voltages on the connector so we do not have to go back and forth to get the info, this will keep the thread short.
              Last edited by budm; 03-29-2018, 11:22 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


                #8
                Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                Roger that. Less than one volt, the set is off, explains the no volts. Hopefully as I learn more I'll be better at reporting the right things.
                They call me......."threadkiller"

                Comment


                  #9
                  Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                  When I found stand-by volts at connector P802 my first thought was the main board is faulty, but I plugged it in and saw no volts at cap C601, expecting around 165 with the set off. Once I found the suspect fets I felt like I was looking in the right place. That's not to say the main board doesn't possibly have a fault but it looks like C601 and the fets are in circuit with one another.

                  I'm still trying to fully understand the switch mode power supply so I may be entirely wrong. If I am don't be afraid to correct that folks, I'd rather look like a n00b than set one of these on fire or even worse someone wind up with a turd.
                  They call me......."threadkiller"

                  Comment


                    #10
                    Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                    Did I miss something budm? Did you need some more voltages/info? Sorry just wondering and thanks.

                    Anyone have any luck on that IC? I still have found nothing.
                    They call me......."threadkiller"

                    Comment


                      #11
                      Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                      Did I run out of road?
                      They call me......."threadkiller"

                      Comment


                        #12
                        Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                        Originally posted by DXseekerMO View Post
                        Roger that. Less than one volt, the set is off, explains the no volts. Hopefully as I learn more I'll be better at reporting the right things.
                        So PS-ON pin does not change state when power switch is toggled, correct?
                        You do have Standby Voltage at this point, correct?

                        The power supply board can be tested by itself without having it connected to the main board by using pull-up 1K resistor between STBY Voltage pin and the PS-ON pin.
                        Last edited by budm; 03-31-2018, 01:18 AM.
                        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


                          #13
                          Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                          I didn't try to toggle the switch while monitoring PS_ON but I will try that and see what happens. At last check 5V standby is still present. What is missing appears to be the 12V voltages after accidentally shorting out EL203 and EL204. 12 volts is present at EL203. I'm guessing I cooked that diode.

                          So when you say "pull up resistor" that is what it's doing, and not a type of resistor. It's just a plain jane 1K brown black red? Does it specifically have to be 1K or can it be close? A 1/4 watt is sufficient?

                          Thanks budm for walking me through this.
                          They call me......."threadkiller"

                          Comment


                            #14
                            Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                            The switched 12V will be present when the main board sends out the PS-ON to turn on the rest of the power supply so you must toggle the power switch to see if it change state or not.
                            The pull-up resistor is used to pull the PS-ON high (no cable between main and power supply), thus called pull-up resistor to simulate HIGH PS-ON signal. 1/4w 470 ~ 1K will be fine.
                            Right now it looks like you have main board problem (due to no BL-ON signal either) and may be the power supply problem too when you shorted it out.
                            You should read my basic troubleshooting guide.
                            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


                              #15
                              Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                              budm, I'm going to do exactly that, read your basic troubleshooting guide. I'm also going to have to re-post voltages. I installed the board back in to the TV and I do have 12V_CC. I also did confirm there is zero volts at BL_ON, 12V_LNB and 12V_AUD.

                              Do you think I cooked that diode? If so you think replacing it may restore my 12V_LNB and 12V_AUD? I still have 12V at EL203.
                              They call me......."threadkiller"

                              Comment


                                #16
                                Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                                Before we move forward I'd just like to say thanks to everyone who's trying to help me get this. Truth told I didn't expect to do it right the first time and I know in advance I'll be screwing up several of these sets before I come to have the knowledge I need. I knew it in advance. I knew I'd muff lots of these up before I got it right.

                                Fifteen years ago I knew practically nothing about auto body and paint. Below is a picture of a car I painted 5 years ago.

                                I guess what I'm saying is when I set my mind to learn something then that's exactly what I do. I make mistakes, I fix them, I learn and someday I master the task. I've always wanted to learn how to fix TV's, and one way or another I will learn exactly how to do that, no matter the time it takes or how many of these sets wind up getting cashed out until I do.

                                I said it in another post, and I'll say it here....I just hope you all don't give up on me because I'm a n00b.

                                Mosfet Q102 is now dead short. I can put the positive probe on the output side of the fuse and the other to ground and it's infinity, but when I touch the gate and drain in both directions....zero ohms.

                                I tried hard, real hard not to short anything when taking measurements, but there's no way to make precise measurements on Gumby....so I took the TV off it's floppy stand and laid it on its front. I wish Ida done that from the start.

                                All I was trying to do was see where the voltage was and where I had it. I was expecting 160V at capacitor C601 with it plugged in and off. I didn't see it so I was checking other places to see where it was and that's when it happened.

                                Anyhow that's how it came to be, right wrong or otherwise. I have to wonder what else got cooked on down the line after this stunt.

                                Here's the car I was talking about. The driver side got in to the cable barrier on I-44 east of Springfield MO. It was a total loss.
                                Attached Files
                                They call me......."threadkiller"

                                Comment


                                  #17
                                  Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                                  Originally posted by DXseekerMO View Post
                                  budm, I'm going to do exactly that, read your basic troubleshooting guide. I'm also going to have to re-post voltages. I installed the board back in to the TV and I do have 12V_CC. I also did confirm there is zero volts at BL_ON, 12V_LNB and 12V_AUD.

                                  Do you think I cooked that diode? If so you think replacing it may restore my 12V_LNB and 12V_AUD? I still have 12V at EL203.
                                  That will involve me tracing out that power supply section to see how ALL the 12V are generated.
                                  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


                                    #18
                                    Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                                    I think for now I'm going to give myself a checkup from the neck-up and look at your article first. You guys are super sharp and knowledgeable, but even with that in my hands I can't be much help without a basic understanding of practical application. After all these aren't hard-wired 1965 Zenith's!

                                    Too bad no one teaches "the basics of electronics and TV repair" locally. This would help a lot, and I wouldn't be wasting all these eggs........ and the towels to wipe them off my face!
                                    They call me......."threadkiller"

                                    Comment


                                      #19
                                      Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                                      @budm thank you for providing that write-up for everyone. I'm beginning to see I have a main board issue most likely. Well at least it did.....until I came along!

                                      Let's try to keep this simple....do you think I'll be able to get away with replacing diode D301 or do you think it's worse than that?

                                      I already planned on replacing those mosfets, including the one I cooked. The board repair kit I found calls for IC U101, fets Q101, Q102 and Q502 to be replaced.

                                      I'm thinking this kit is available for power supplies with shorted fets....and that's what I did......so I'm wondering with this info do you think these components have a good chance at resolving the damage I did? It would be cool if you could help me track it down, but I don't want this to become a pain in your

                                      I'm going to place an electronics order soon and would like to see if I can get the power supply back up and running for further diagnosis?
                                      They call me......."threadkiller"

                                      Comment


                                        #20
                                        Re: Toshiba 50L1350U pk101w0050i troubleshooting, help identifying an IC?

                                        Sometimes the answers we seek are found without a word spoken, so I guess I'm done with this.
                                        They call me......."threadkiller"

                                        Comment

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