LG 50PM680 No picture, sound working

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Tom3dJay
    Member
    • Oct 2014
    • 10
    • Czech republic

    #1

    LG 50PM680 No picture, sound working

    Hello guys, I'm new to your forum, but I've done some extensive reading already.
    I'll cut straight do the point here:

    My set gives me no picture, sound is working, but If I remove upper buffer completely, I'll get picture on the lower half of the screen.
    Part number for the upper buffer is EAX64300101, it's used in other LG plasma sets too.
    There's only one visible problem with the top buffer: IC chips got slight "dark" mark in the corner, but it doesn't smell burned at all and I've seen couple boards online with this type of darker corner, so I don't really know.

    What do you guys think? It's it sole upper buffer failure or is the panel dead?

    (everything else seems to be in order, no bad caps or fuses)
    Attached Files
  • MagicSmoke
    Badcaps Veteran
    • Feb 2011
    • 275
    • USA

    #2
    Re: LG 50PM680 No picture, sound working

    Watch this video to test your buffer. The chips can fail with no visible damage.

    https://www.youtube.com/watch?v=51SZ...Y&noredirect=1

    Comment

    • Tom3dJay
      Member
      • Oct 2014
      • 10
      • Czech republic

      #3
      Re: LG 50PM680 No picture, sound working

      Originally posted by MagicSmoke
      Watch this video to test your buffer. The chips can fail with no visible damage.

      https://www.youtube.com/watch?v=51SZ...Y&noredirect=1
      Thanks for swift reply. Definitely a good vid, but I'll have to borrow the multimeter later, since don't have one.

      What if the buffer tests okay?

      This is one of LG series sets with razor thin edge, potentially suffering from ribbon damage due to design flaw.

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: LG 50PM680 No picture, sound working

        There is a good possibility that the Y-scan ribbon is damaged, which is fatal to the panel. But, usually only happens on the top most chip.
        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

        Comment

        • Tom3dJay
          Member
          • Oct 2014
          • 10
          • Czech republic

          #5
          Re: LG 50PM680 No picture, sound working

          Thanks a lot boys, I'll get back to you once I check for short on the upper buffer.

          Comment

          • Tom3dJay
            Member
            • Oct 2014
            • 10
            • Czech republic

            #6
            Re: LG 50PM680 No picture, sound working

            Small update:

            I measured the resistance on the upper buffer, and found out that only couple pins give me any good reading, so I guess ICs are dead.

            Another problem is, the lower part of the picture stopped working too. I suspect it may be some mistake on my part when I was trying to unplug the y-sus (while powered off). Possibly even mechanical damage, but I couldn't find anything wrong.

            It's really difficult to get the lower buffer unplugged, so I measured it while still plugged to ribbons panel and y-sus and seems like everything is now dead on the lower board too, resistance shows "1" no matter what ohm scale I choose on the multi meter.

            Y-sus is still buzzing, gives good "switching on" sound so I don't suspect it being dead, I checked the ribbons too, and the seem to be alright.

            How would you proceed? Thanks in advance for any suggestions, you guys are awesome.

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: LG 50PM680 No picture, sound working

              The pins should normally appear open - the internal structure is a MOSFET with an antiparallel diode. A low resistance reading in both directions is bad.
              Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
              For service manual, schematic, boardview (board view), datasheet, cad - use our search.

              Comment

              • Tom3dJay
                Member
                • Oct 2014
                • 10
                • Czech republic

                #8
                Re: LG 50PM680 No picture, sound working

                Alright, that makes sense actually, the upper gives me close to zero both ways on couple pins.

                This is the resistance on the lower buffer. Upper gives me half of that on all pins, except for couple pins on top, which gives zero both was.
                Attached Files

                Comment

                • Tom3dJay
                  Member
                  • Oct 2014
                  • 10
                  • Czech republic

                  #9
                  Re: LG 50PM680 No picture, sound working

                  Hey, guys, small update, I just bought y sus and both buffer boards!

                  Unfortunately, this didn't fix the problem completely.

                  Now I'm getting very quick picture blink accompanied with the with classical switch and buzz sound, but buzzing sound goes away at the same time that picture does.

                  Any idea what's wrong?

                  Comment

                  • Tom3dJay
                    Member
                    • Oct 2014
                    • 10
                    • Czech republic

                    #10
                    Re: LG 50PM680 No picture, sound working

                    bump

                    The led light on main board gives long-short -- long-short signal.

                    Comment

                    • ned1
                      Senior Member
                      • Feb 2014
                      • 139
                      • usa

                      #11
                      Re: LG 50PM680 No picture, sound working

                      you had bad upper buffer. If you removed upper buffer and got picture on lower screen then that was all you need to change. Put back your old y-systain and lower buffer and install new buffer. Make sure your new buffer is not short.

                      Comment

                      • Tom3dJay
                        Member
                        • Oct 2014
                        • 10
                        • Czech republic

                        #12
                        Re: LG 50PM680 No picture, sound working

                        Originally posted by ned1
                        you had bad upper buffer. If you removed upper buffer and got picture on lower screen then that was all you need to change. Put back your old y-systain and lower buffer and install new buffer. Make sure your new buffer is not short.
                        Oh, I think I forgot to update the thread, but picture went gone shortly after.

                        I'm not really sure what caused it, perhaps bad handling of components or maybe some type of short while measuring, no clue.

                        That's why I bought some buffers and y-sus.

                        Comment

                        Related Topics

                        Collapse

                        • howardc64
                          A1312 (27” iMac 2009-2011) A1407 (Thunderbolt Display) A1316 (Cinema Display) Display Black Screen Repair
                          by howardc64
                          Problem

                          This is an LG edge LED lit LCD Display. The LEDs are on the bottom edge of the display. There are 2 bars (left and right) Each bar has many LEDs and a 6 pin connector. Each pin drive several LEDs thus is the highest current flow / heat junction. The weak lead free solder gradually fails with thermal expansion/contraction cycling and increases resistance. PSU will compensate up to a point, then when the current is too high, PSU just shut down the backlight causing a dark display. I have even seen one which the connector just fell off as solder points became completely detached....
                          08-04-2024, 10:36 PM
                        • TR103
                          Samsung TV model UE50TU: rebooting, backlight, sound, but no picture
                          by TR103
                          Hi, I have a Samsung UE50TU with:
                          - sound and backlight, but no picture
                          - when it arrived, it had a picture for a few seconds
                          - it keeps rebooting
                          - without ribbon cable between the two panel boards, it does not reboot but I have no picture
                          - without cable between mainboard and lcd panel, it does not reboot (but obviously i have no picture)
                          - when i try a tape fix, its keeps rebooting, unless I tape off pin 1 (the innermost pin). In that case it does not reboot but I have no picture.

                          - without cable between mainboard and lcd panel and with a jumpered...
                          01-22-2025, 04:12 PM
                        • Mgiffune
                          Samsung UN60EH6000F Black Screen, Backlight and Sound Good. Power Cycle Returns Picture
                          by Mgiffune
                          I have a 60 inch Samsung UN60EH6000F flatscreen TV. The screen went black a few months ago Sound is good, backlight is good, no menu. I replaced the TCon board with a used board purchased from Ebay. It worked fine for a 3-4 months, then the screen started ‘fading' back. Once again, sound is good, backlight is good, no menu. However, this time the picture looks fine for about 10-15 minutes, then fades back. If I power cycle the TV, the display reappears, for another 10-15 minutes, then fades black again. Repeatable ever time.

                          I ordered a supposedly ‘new' Tcon board this time, and
                          ...
                          06-09-2024, 10:28 AM
                        • Ierwin
                          Samsung UE60KU6079 backlight okay mainboard responsive, no picture, no sound
                          by Ierwin
                          Hello everyone,
                          Ive got a UE60KU6079 on the workbench that is giving me some headaches trying to troubleshoot.
                          The previous owner stated that there had been white dots on the screen which from the description sounded like some lenses fell of the backlight LEDs.
                          He had opened the TV from the back, trying to get to the backlight, supposedly gave up, reassebled everything and gave the TV to me.
                          I expected the worst like ripped COF cables or a cracked panel but could not find anything like that yet.
                          Anyway I still fully expect that there has been something seriously damaged...
                          05-13-2025, 03:31 PM
                        • jchang
                          Samsung UN70NU6900F no picture and no sound
                          by jchang
                          Hi all

                          I was just given a Samsung TV with the issue. I read various threads and videos and attempted the ribbon tape method to gain an image, but no luck.



                          Symptom:
                          No picture no sound.
                          When I plug in the power cord, Backlight LED turns on for a half second and then turns off. The red LED next to the power button located center bottom flashes 2 or 3 times. When the power button is pressed after, it does the same thing.
                          No sound at all.



                          What I tried:
                          1. I tried unplugging the left or right ribbon...
                          01-09-2023, 06:28 PM
                        • Loading...
                        • No more items.
                        Working...