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    #1

    Another cycling, screeching Samsung plasma.

    Hi all. I have a cycling and screeching Samsung plasma that I have found described many times with various fixes. To be more descriptive, about a year ago, it started taking two or three tries to start. Last month, it was up to about a half hour of cycling on and off with various rainbow snowy pictures and screeching noises. By Thanksgiving, it would not start at all most of the time, but every now and then it gets lucky. If it does start, it's good until it is turned off.

    Model : PN58A550S1FXZA
    Logic Board : BN96-07703A
    Power Board : BN44-00183A

    When I started, I found all the bad cap threads and thought I had the golden fix. Sure enough, I started removing caps from the power board to test with a calibrated LCR meter and they were pretty degraded. I replaced all the caps for the low voltage supplies, but I left the high voltage caps alone because my HV test points were right on when measured and I read somewhere that the low V ones were the more common failures. I also did not replace a bunch of caps on the hot side of the hot/cold divider line because they measured okay. I was disappointed that this did not fix the problem.

    I then found a thread where someone with this same problem re-flowed the logic board and fixed it. I re-flowed mine and it didn't change, but to be sure, I ordered a replacement logic board... and it didn't change.

    So back on suspecting the power board, I re-checked all the voltages coming off the four output connectors. I have verified the following...

    VS 202V
    VA 65V
    VG 15V
    Vamp 18V
    D5.3 5.3V
    12V

    I had previously inspected for cold solder and bulging components on the power board and nothing jumped out. Before I started posting this, I figured I should give it another thorough look since I see that pictures are normally requested. Okay, so none of the solder on this thing would pass inspection where I work, but I don't really think that any of it is bad enough to cause this either. But, maybe I should take it in to work anyway and re-flow everything I can just in case.

    So, assuming that my re-flow attack doesn't work, where do I go next? I know you'll probably want pictures, but my camera batteries aren't holding a charge and I don't have a smart phone... so it may be a day or two on that.

    Thanks.
    Last edited by mc68hc11a1p; 12-16-2013, 02:02 PM.
    Tags: None
    #2
    Re: Another cycling, screeching Samsung plasma.

    https://www.badcaps.net/forum/showthread.php?t=26790

    Comment

      #3
      Re: Another cycling, screeching Samsung plasma.

      I re-flowed everything I could find on the power board at work last night, but no change. Right now, I have the jumper installed on the control board and when I first turned it on, it was a solid white screen, followed by solid green, then red. It cycled through this a few times and it seemed like it would keep going, but now it is cycling power again.
      Attached Files

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        #4
        Re: Another cycling, screeching Samsung plasma.

        Originally posted by mc68hc11a1p View Post
        I re-flowed everything I could find on the power board at work last night, but no change. Right now, I have the jumper installed on the control board and when I first turned it on, it was a solid white screen, followed by solid green, then red. It cycled through this a few times and it seemed like it would keep going, but now it is cycling power again.
        unplug for 20 seconds from mains... then try again with the jumper in place... See test patterns again?

        Comment

          #5
          Re: Another cycling, screeching Samsung plasma.

          The test patterns are there, but the power still cycles.

          Comment

            #6
            Re: Another cycling, screeching Samsung plasma.

            I'm pointing my finger at the main here.... the psu may be detecting the main is disconnected and rebooting, But test patterns show everything else is working fine.

            let one of the guys with a little more experience with plasma's take a look at this and see what they say

            Comment

              #7
              Re: Another cycling, screeching Samsung plasma.

              Oh boy, am I a dummy. I seem to have gotten the main board and the control board confused. I baked and replaced the control board but it was the main board that the guy in the other forum suggested. Well, I could have saved myself a hundred bucks between the caps and that board if I could actually read. I just baked the main board and it is fixed.

              Thank you very much for your assistance. I am so relieved and I literally could feel the stress lift and float away.

              Comment

                #8
                Re: Another cycling, screeching Samsung plasma.

                How have you "baked" it exactly?

                Comment

                  #9
                  Re: Another cycling, screeching Samsung plasma.

                  I propped it up with tin foil balls on the corners, placed it on a cookie sheet, and baked it at 375 for 10 minutes to attempt to re-flow the solder on the BGA's. It is a common procedure that has actually fixed this screeching/cycling problem for many folks with my model. That was why I was so disappointed that it didn't work for mine, but it turned out I just baked the wrong board last time.

                  Comment

                    #10
                    Re: Another cycling, screeching Samsung plasma.

                    Originally posted by mc68hc11a1p View Post
                    I propped it up with tin foil balls on the corners, placed it on a cookie sheet, and baked it at 375 for 10 minutes to attempt to re-flow the solder on the BGA's. It is a common procedure that has actually fixed this screeching/cycling problem for many folks with my model. That was why I was so disappointed that it didn't work for mine, but it turned out I just baked the wrong board last time.
                    That will not last!

                    Comment

                      #11
                      Re: Another cycling, screeching Samsung plasma.

                      That's okay... I can use a real re-flow oven at work next time it starts mis-behaving and we have an x-ray machine to inspect the BGA's. At least I know what the fix is now. I will enjoy this while it lasts because this is the first time in over a year that this thing is turning on in one try.

                      Comment

                        #12
                        Re: Another cycling, screeching Samsung plasma.

                        fair enough

                        Enjoy your TV

                        Comment

                          #13
                          Re: Another cycling, screeching Samsung plasma.

                          You have a bad power supply board.

                          Reflowing will not help because what's bad is not a junction, but a component.

                          Reflowing, like a sirgical operation, is a risky process. It can save from dying (or , in electrical world, the dead), but it may also kill the living.

                          It is the last thing I'd do unless I have a reliable history of a particular failure on a particular board, like the three lights of death on XBOX or image deformations on older laptops.

                          The source of this problem is most likely a failure on the power supply board.

                          I can't say more because I am held by two different corporate policies - one prohibiting to disclose too much and the other prohibiting from advertising.

                          But, to reassure you, the problem is most likely the power supply. True story :-)

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