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Pioneer PDP-V402 - Black Horizontal Lines

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    Pioneer PDP-V402 - Black Horizontal Lines

    Hi, I'm new around here and hoping that there may still be some people on here that are knowledgable about plasma display repair, as some of the old badcaps forum posts have been pretty useful to me so far.

    For any regular plasma TV I probably wouldn't bother to go through this effort, but I have a pro-grade Pioneer plasma which I really want to use and it would be a shame to throw it out since there's not many of them still around these days. The plasma has the typical black horizontal lines that seem plague plasma displays. I've counted 3 lines on top of the screen and 4 at the bottom. The previous owner said they were initially intermittent, but in my experience so far they haven't gone away.

    From reading other posts, the usual causes for these black horizontal lines seem to be either:
    A. Dirty ribbon cables/connectors that connect the Y-Buffer boards to the panel.
    B. Faulty ICs on the Y-Buffer boards
    C. I've seen numerous people state that the panel can “go bad” and the lines can appear (not sure if this is even true) as no real explanation was given.
    D. Saw one mention of the digital board, but I haven't looked into this yet.

    Regarding C., I've seen the ribbon cables either blow out due to overheating or corrosion on the panel side, so perhaps this is what those people were referring to. I'd assume this is repairable under the microscope but I'm not sure whether or not the ribbon cables on the panel side are typically accessible?

    So far I've reseated and cleaned the top & bottom ribbon cables, twice, with no luck or change whatsoever. Moreover, I've tested the top & bottom Y-buffer boards for any shorts, along with a visual inspection and everything checks out just fine.

    The next thing on my list is to get to the panel and inspect the ribbon cables there (if they're even accessible). I'm wondering if anyone has any other recommendations on a possible fix, or something else to look at before I go through the effort to strip it down to the panel.

    Any comments are much appreciated.

    Best regards,

    William

    #2
    Re: Pioneer Plasma - Black Horizontal Lines

    No model mentioned and no photos.

    Definitely nothing to do with Y boards, it's panel or the COFs that come out and connect to the upper and/or bottom boards that have a large horizontal heatsink.

    Comment


      #3
      Re: Pioneer Plasma - Black Horizontal Lines

      You can either try replacing the buffer board, or you will need to scope the drive signals going to the panel to prove 100% where the problem is. Yes the panel can go bad and cause this, some Samsung 50" plasmas had this problem.

      Comment


        #4
        Re: Pioneer Plasma - Black Horizontal Lines

        Thanks both for your comments.

        Apologies, for not including the model & photos. Here model no. + service manual:

        https://www.manualslib.com/manual/11...-Pdp-V402.html

        Pictures of internals and lines attached. Please ignore the yellow tint, the image is white in real life. It's just the camera.

        Sad to hear it may be the panel, but that's what I expect to be honest. I still think it could be the ribbon cables which connect the Y buffer boards to the panel though.

        The unit has 6490 hours on it which is not much but these can get quite hot hence the 7 fans.

        You really think replacing the buffer board is a good idea? I recently got a scope so could give that a try first…
        Attached Files

        Comment


          #5
          Re: Pioneer Plasma - Black Horizontal Lines

          Okay, for some reason I read vertical lines, sorry.

          It has to do with panel, Y-buffers, Y-SUS,or logic board.

          Each pin that the buffers connect to the panel have a forward voltage that can be measured by a multimeter, if it measures open, then the board is faulty.

          To test it you put a multimeter in diode mode, place positive lead on Y-Buffers floating ground, and negative on each pin that connects to the panel, it must give a voltage of 0.6~1.0V

          Comment


            #6
            Re: Pioneer Plasma - Black Horizontal Lines

            Originally posted by Biruslapio View Post
            Okay, for some reason I read vertical lines, sorry.

            It has to do with panel, Y-buffers, Y-SUS,or logic board.

            Each pin that the buffers connect to the panel have a forward voltage that can be measured by a multimeter, if it measures open, then the board is faulty.

            To test it you put a multimeter in diode mode, place positive lead on Y-Buffers floating ground, and negative on each pin that connects to the panel, it must give a voltage of 0.6~1.0V
            No problem.

            Funnily enough, I spoke to a repairman who used to work on these. He said:
            "Best guess, it's one of the IC scans but difficult to know for sure without having the panel here. You could look closely at each chip and see if there's a hint of a circle in the middle, could be a sign of failure. The board they're on is bonded to the glass so it means a component level repair or scrapping the panel."
            Perhaps he also is thinking it's vertical lines... Also I have no idea which board he is referring to as I haven't stripped the monitor down to the panel yet.

            As for your suggestion, so far I've only done a continuity test between GND & each of pin that connects the buffers to the panel. I'll try and put it into diode mode and measure as you suggest on the weekend.

            Will post back with results

            Comment


              #7
              Re: Pioneer PDP-V402 - Black Horizontal Lines

              Looking in the service manual, the lower scan modules (A) (AXF1104) are both the same but different from the upper scan modules (B) (AXF1105)
              So you should be able to swap the upper modules around with each other.

              DO NOT swap a lower board with an upper board
              Last edited by R_J; 04-11-2022, 01:25 PM.

              Comment


                #8
                Re: Pioneer PDP-V402 - Black Horizontal Lines

                Originally posted by R_J View Post
                Looking in the service manual, the lower scan modules (A) (AXF1104) are both the same but different from the upper scan modules (B) (AXF1105)
                So you should be able to swap the upper modules around with each other.

                DO NOT swap a lower board with an upper board
                Yeah, those are the Y-buffers. There are four of them, two top and two bottom. Each set does indeed have different part no's, but otherwise they're visually identical.

                I removed one yesterday to inspect it, but didn't think to swap the upper modules around with each other, then try the same with the bottom pair. That's a good idea to rule out these boards.

                Sadly I don't have the space on my bench during the week to work on this so will report back with results this weekend!
                Attached Files

                Comment

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