Announcement

Collapse
No announcement yet.

Panasonic TC-50AS630 No Image - Blinking LED

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Panasonic TC-50AS630 No Image - Blinking LED

    Hello good people, I have another unit here which is giving me problems. Upon plugging the unit it, after a few seconds the front LED will start blinking 3 times in a row and repeating indefinitely. No image or sound.

    The first thing I checked was the backlight. It's a single vertical strip on one side of the panel which has 8 groups of 7 LEDs. (Part #V500D2-LS1-TREM3) I used a backlight tester and each group lit up without issue.

    The standby 5.3V is good, the 16V and 24V from the PSU board both come up for a few seconds while the TV_SUB_ON signal is high. Both 16V and 24V stay on when forced. I also tried to force the backlight on but the LED driver board keeps resetting - it comes up to about 55V and resets about once a second making the backlight flash repeatedly. It requires a PWM signal which I did not provide, which is possible why it would not stay on?

    The LED driver board never receives a BL_ON signal from the A board which would make sense given that the PNL12V output never turns on. For some reason the A board is unhappy and doesn't want to enable the 12V regulator. I noticed that when the A board receives the 16V input, an ERR pin goes high at about the same time, then the TV_SUB_ON signal goes low and the power board turns off.

    While troubleshooting I stumbled across this Panasonic "Technical guide" which references this model. It's kind of like a watered down service manual as it features somewhat high level schematics but still a lot of useful info: https://service.panasonic.ca/pcs/EXT...uide_Final.pdf

    Here's the power on procedure from the technical guide and it shows how far mine gets.


    Additionally here's the P and A board "schematic"


    I was able to find some of the IC's that are supposed to be turned on by the F15V signal:

    IC Expected Measured
    IC8704 5V 5V
    IC8705 3.3V 3.3V
    IC8100 1.1V 0V
    IC8101 1.5V 0V
    IC5704 1.8V 0.6V
    IC8715 3.3V Can't locate
    IC5702 1.2V Can't locate
    Last edited by itachi; 01-05-2021, 12:20 AM.

    #2
    Re: Panasonic TC-50AS630 No Image - Blinking LED

    What is PA2002? Do you have the manual?
    Willing to help but I'm no expert.

    Comment


      #3
      Re: Panasonic TC-50AS630 No Image - Blinking LED

      Please upload the service manual you are using so we will on the same page.
      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


        #4
        Re: Panasonic TC-50AS630 No Image - Blinking LED

        The 3 blinks is a diagnostic code. What is the error listed as in the service manual?

        Working on a Panasonic currently with a service manual. PA prefixes are surface mount fuses. Service manual also has grid locations to help find components. Search the designator within the PDF.
        Last edited by neilc6; 01-05-2021, 06:42 PM.

        Comment


          #5
          Re: Panasonic TC-50AS630 No Image - Blinking LED

          Originally posted by neilc6 View Post
          PA prefixes are surface mount fuses. .
          Thanks Neilc6 That fuse is what I would check next.
          Willing to help but I'm no expert.

          Comment


            #6
            Re: Panasonic TC-50AS630 No Image - Blinking LED

            Service manual
            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: Panasonic TC-50AS630 No Image - Blinking LED

              Originally posted by budm View Post
              Service manual
              Thanks for that! I only had the technical manual which was a bit limited. So as it turns out that PA2002 fuse is in fact blown. It's unlabeled on the board but it's marked with an 'X' on the back of the board near the top middle.

              I'm assuming it blew for a reason and should just replace the entire A board at this point.

              Edit: I can't seem to find the mainboard in stock online new or used. But I can find the Pansonic branded BGA which is powered by the SUB 1.1V and 1.5V rails. I'll see if I can narrow it down to the 1.1V or 1.5V rail that's causing the overcurrent. Maybe I'll get lucky and it'll be a faulty ceramic capacitor.
              Last edited by itachi; 01-07-2021, 06:26 AM.

              Comment


                #8
                Re: Panasonic TC-50AS630 No Image - Blinking LED

                Measure the resistance from the fuse pad to chassis for each side of the fuse and see what the resistances are?
                Willing to help but I'm no expert.

                Comment


                  #9
                  Re: Panasonic TC-50AS630 No Image - Blinking LED

                  Originally posted by dick_barton View Post
                  Measure the resistance from the fuse pad to chassis for each side of the fuse and see what the resistances are?
                  It's high on both sides. 10k on the input and 20k downstream.

                  The issue seems to stem from the 1.1V rail. I was measuring the resistance on that rail and by heating up the main BGA I was able to make the resistance drop from ~50ohms to less than 5.

                  Comment


                    #10
                    Re: Panasonic TC-50AS630 No Image - Blinking LED

                    Searched the internet and it appears that this fuse, part number K5H4022A0031, is a 32V, 4A fuse. I cannot see that if the 1.1V supply was driving into 5 ohms would blow this fuse because this would be equivalent to a current of 220mA.

                    https://tinyurl.com/y695asxa

                    What is the resistance from TP8100 to chassis and TP8101 to chassis?
                    Last edited by dick_barton; 01-07-2021, 07:13 AM.
                    Willing to help but I'm no expert.

                    Comment

                    Working...
                    X