Question about Samsung PS42C91HDX 42 in. Plasma TV

1 Answer

Hi, Samsung plasma TV PS42C91H. The picture freezes exactly 2 minutes after switching it on. Switching it off and on again reestablishes the picture for another 2 minutes and the cycle repeats itself. The sound is perfectly ok and one can hear that the TV reacts to any sound changes activated by the remote while the picture is frozen. (You can see that two frames keep being swapped alternatively) If during the two minutes the TV is functioning normally one select "source" then the picture freezes black immediately. Again switching off - on reestablishes back to normal, for another 2 minutes. I am an engineer so I would like to pinpoint the faulty board in order to replace it, as it is cumbersone to take the large TV to a repair shop!. Regards Alberto

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  • 6 more comments 
  • Alberto Sartini May 06, 2010

    Thank you so much for the prompt response!
    Ok, I just tried the following:
    I have Satellite TV, digital, in AV1, then a DVD on AV2 and my laptop on PC.
    The TV freezes regardless of which input I am using but if it is still running (less than 2 minutes) and I change the source the picture goes black but you can hear that you can rotate through the sources pressing the source button on the remote. So the selection is still working fine without a picture.

    If I press the still button on the remote while the TV is working properly this function works perfectly ok. If I press it after it has frozen then it has no effect.

    Please specify more details of the board as I have not yet opened the TV, like its location so I will be sure I get the correct board.

    Many thanks


  • Alberto Sartini May 06, 2010

    I´ll do it now. Take a couple of minutes and I´ll get back to you

  • Alberto Sartini May 06, 2010

    Ok, I have taken the back cover off.
    I guess the main board is the one with the connectors. No problem to take it out but I wait for your next instruction to see if I can get if fixed by tomorrow!.



  • Alberto Sartini May 06, 2010

    Ok, I will do but I measure the time to be exactly 120 seconds everytime, so it looked to me to be a digital problem.
    I´ll try right now


  • Alberto Sartini May 06, 2010

    What we hate in electronics: now is working fine and has not frozen.

    Changing sources works fine, so I guess I will have to leave it for tonight.

    Maybe I should put contact cleaner on the various connectors in case is a false contact somewhere.

    I know slightly that board in various places and nothing happens.

    So if it is ok with you we ill watch it tomorrow. If it happens again I will try the fan and maybe some freezing spray on some components at the time, and see.

    Best regards and many thanks for your help.


  • Alberto Sartini May 07, 2010

    Hi there,

    Guess what?
    Yes, the TV is still working without a fault so I had no chance to spray some antifreeze.
    I will wait for tomorrow in case, otherwise I will thank you and close the case.
    Tomorrow, Sunday, I will clean all connectors with contact cleaner, just in case.
    Like I said, I am a hands on Engineer although these days I do management. In my previous job I had 65 software engineers working for me. Now in this place (Thales South Africa) I have a group of 20 doing hardware design.
    Before that I was the chief system engineer for the weapon system of Rooivalk, the South African equivalent to Apache helicopter and when I was student I used to build radios and TVs (the valve kind! LOL)
    I am saying all this because I appreciate your help and I have no circuit diagram of the TV. Do you kw any place on the web where I can get it?
    By the way these days I also built cars like my BMW 325i from scratch and taking parts from a smashed vehicle.
    Anyway, when we get older (62 here) we tend to chat too much!
    Thanks again

  • Alberto Sartini May 07, 2010

    Hi Barbu,

    Ok, I see you are a baby but not a teenager!! LOL.

    Yes, I will accept now and I will let you know in a few days if anything happen.

    And should it be a problem with a dry joint then I would rather get a new board.

    At work when we deal with large multilayer boards that we may have designed ourselves, we send them outside to remove components, we don´t even try to do it in house anymore.

    Best regards


  • Alberto Sartini May 07, 2010

    yes, i am very impressed with the efficiency and super quick turn around times. Alberto



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Hi alberto
The problem you described is usually associated with the main/signal processing board.
But i`d have a few basic questions first so bear with me.
Although i don`t have details of your setup,did you try different inputs(analog and digital) ?
Does the freeze function (still button on the remote) make any difference?

Posted on May 06, 2010

  • 3 more comments 
  • Jacques Marin
    Jacques Marin May 06, 2010

    Hi again alberto

    So it does sound like a main/digital board problem and the next step is to pull the back off.

    The main board will have all the inputs connected to it, and as a matter of fact pretty much all the boards will be connected to it as well.

    Once you`ve identified that board let me know and we`ll try something to pinpoint the problem.

  • Jacques Marin
    Jacques Marin May 06, 2010

    O.k Alberto

    You were saying that it takes a couple of minutes before it started to act up.

    So that tells me that the problem might be thermal: a part breaks down when heated up.

    If you have a fan you could set it up over the main board to see if you can extend the time that it takes before acting up.

  • Jacques Marin
    Jacques Marin May 06, 2010

    Depending on the size of your fan;

    Try to concentrate on the large processors.

    Usually in a repair shop we use Freeze spray to pinpoint the problem to a single component.

    But at least now , it might help to verify which board is the problem.

  • Jacques Marin
    Jacques Marin May 06, 2010

    LOL this is funny

    I know what you mean: just like going to the dentist :)

    I`ll be around tomorrow at about the same time, talk to you then.

  • Jacques Marin
    Jacques Marin May 07, 2010

    G`day Alberto

    Thats o.k about the chatting , i`m not far behind you (52) and beside i might need some help fixing my chopper some day here in canada.LOL

    About the tv now;

    It might just be as simple as an oxidized connector that you disturbed when you removed the back panel.

    So if you have some contact cleaner you could pull out the connectors and spray them.

    Other scenario could be a cold solder joint that could be hell to find in a board loaded with surface mounted components.

    In any case even if you accept this solution, the post remains open for further comments(or chat) and it will be my pleasure to continue this conversation .

    There is also the fact that if the post stays open:

    If you send a new comment and i don`t answer it within four hours then it gets automatically re-posted and you`ll end up having to start over again with another feller in here.

    Cheers and looking for further development.



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