50LGPK590 Common Problem Sound But No Video

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  • omendata
    Member
    • Jun 2015
    • 25
    • United Kingdom

    #1

    50LGPK590 Common Problem Sound But No Video

    This is a nightmare common fault with plasmas and difficult to pin down.

    The tv just didnt come on one morning and had the usual psu relay click and standby light.

    I have repaired the psu which i thought was the issue - common problem with the two 22ohm 5 watt resistors and sometimes a diode and smps transistor on the LG PK range of televisions but the tv powers up now so I was nearly jumping for joy...until...

    Just very depressing that i also have no picture but have sound now so it seems another board on the telly caused the psu resistor to blow - incidentally its usually the top resistor but i replaced both just to be safe.

    I have tested the y-buffers today and they are fine - i bought a y sustain board off ebay and fitted it after testing the y-buffer boards were ok - it didnt fix the issue.

    Someone has said that if you pull the connection from the z-sus to the psu and you still have sound then its the z-sus board that has the fault but i dont agree with this - perhaps someone on here can confirm this as i pulled the z-sus and there is still sound indicating that z-sus board is faulty.

    Having researched for two days it seems the problem may be with the actual t-con board itself.

    I think i will bite the bullet and buy a t-con board tonight and see what happens as I am sure its not the z-sus even though the advice is that it is if you still get sound when its disconnected.

    Maybe someone more knowledgeable than i on here can give us some sort of clue.

    I really need to get an oscilloscope to fix these things properly.
    I have always got on fine with my fluke meter but for more in depth stuff like this you need and oscilloscope especially for testing the y-sus outputs.

    Someone mentioned the service port on the back of the tv that repair shops use to repair tv so i connected up an rs232 cable and can now control my television via my pc using the service port but having tried to run a self diagnostic i have found that the so called "SERVICE PORT" is not a service port at all and repair shops cannot use it to diagnose a fault its merely there to allow programming of the firmware and controlling the television unless someone know what the diagnostic command is to run a self test but i doubt it would pinpoint the issue. This also makes me pretty certain that the main board is ok and its either the z-sus or more likely the t-con board.
    You are only too old when you say you are too old!!!
  • Hamie
    Badcaps Legend
    • Apr 2014
    • 1383
    • UK

    #2
    Re: 50LGPK590 Common Problem Sound But No Video

    Another 50pk590! These are breaking down in big numbers.
    Probably a mainboard fault.
    Read through this thread:

    Comment

    • Hamie
      Badcaps Legend
      • Apr 2014
      • 1383
      • UK

      #3
      Re: 50LGPK590 Common Problem Sound But No Video

      https://www.badcaps.net/forum/showthread.php?t=47874

      Comment

      • Hamie
        Badcaps Legend
        • Apr 2014
        • 1383
        • UK

        #4
        Re: 50LGPK590 Common Problem Sound But No Video

        Do the test patterns test first.

        Comment

        • omendata
          Member
          • Jun 2015
          • 25
          • United Kingdom

          #5
          Re: 50LGPK590 Common Problem Sound But No Video

          Thanks, at last someone who knows what they are talking about.

          So this model is a bit of a lemon is it - bummer its got some great functionality and the picture isnt bad either but as with all plasmas the ridiculous y-sus system really is a pig - at least the y buffers on this model have heatsinks i have seen some really poor y-buffers with no heatsinks - should be mandatory to have a heatsink on those chips.

          Will check fully tomorrow and get back to you Hamie.

          Hopefully I can get this sorted as the nag level is at 9 (on the girlfriend-nag scale) if she cant watch Big Bang Theory in full 50 inches - what is it with size i am quite happy with my 24 inch Dell ST2220L lol
          As you are also a fellow Scot, if you help me fix this I owe you a few pints - You dont want to take a nagging girlfriend off my hands do you!
          dlol
          >;o)

          Many thanks

          Omen
          Last edited by omendata; 07-26-2015, 04:31 PM.
          You are only too old when you say you are too old!!!

          Comment

          • omendata
            Member
            • Jun 2015
            • 25
            • United Kingdom

            #6
            Re: 50LGPK590 Common Problem Sound But No Video

            Ok couldnt wait had to check it now.
            Bridged the two connection points near P104 on the t-con board.

            I am getting no test patterns at all so I presume the T-Con is bad for sure now!

            The funny thing is that only hdmi1 is working its all i am getting sound out of - plugging the same device into hdmi2 or 3 and changing channel with the remote gets no sound so i had thought this might
            indicate a problem with the main board but i saw a youtube guy who had been struggling for weeks replacing everything on board until he tried the t-con on his 50PK590 and that fixed it.

            The main board is also getting an ip address from my home isa server via the rj45 port suggesting that its firmware is working and i can ping it fine.

            This tv has only lasted 4 years - I had a Bush old crt that lasted for 15 years and a Marconiphone that lasted for 25 years - New technology eh.
            I have learned a lesson anyway - never buy Samsung or LG should have gone for a Panasonic and not been such a tight-arse.

            I used to work for the JVC plant up in East Kilbride and all our engineers had Panasonics at home - that says a lot.
            Our JVC tellys were utterly the worst - If you ever see a JVC telly with an EK prefix - Avoid it like the plague.
            We had the monkeys on the assembly line inserting coke cans between the electrodes and loads of other stuff you wouldnt believe.
            The AIS department used to smoke dope every night during the nightshift and one guy got his finger cut off , another lost his hand - Unbelievable.
            No wonder the factory shut down especially after the main shipping manager was arrested by CID for shipping tvs out to his own customers.
            Everyone wondered why he could afford such an expensive house in Stewartfield hmmmm

            I digress however so you think the t-con could be the problem then?
            I just hope its not one of those multiple board cascading failures.#
            Last edited by omendata; 07-26-2015, 05:40 PM.
            You are only too old when you say you are too old!!!

            Comment

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