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Help repairing Samsung ps50c450

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    Help repairing Samsung ps50c450

    Hi There!

    I am currently trying to repair a TV that I bought (as broken, very cheap) 1 yr ago and tried to repair. It's a 50" plasma Samsung TV. It originally had a "clicking no start condition". There has been 2 phases for this so let me explain:

    Past (1 yr ago): TV wouldn't turn on. PS was clicking. Found that after disconecting X board it would start up internally (samsung start up tune) and all power leads (Vs, Ve...) would check good. Found a shorted transistor shorted in the X board so I swapped it (I know it's advised to replace ALL semiconductors, I tried to go cheap). Checked TV afterwards and didn't want to turn on. Got sick of it and left TV sitting for 1 year

    Present. Brought the TV back to the bench: First test: Hit power button on remote, relay clicks on, samsung start up tune sounds ok. Blank screen. Remote buttons make the status led blink. In the rear: Vs, Ve...all dead. Only low voltages present (Stand-by, 5.3v...). Actually... Logic board seems dead as no light is on neither blinking.

    I realize there's an SMD fuse on the logic board. Checked it, its OPEN. Its marked F2000, F5R (as per datasheet, 5Amps). One lead of the fuse comes from power socket, 5.3V, straight from Power Supply. Other lead checks fully grounded, 0.000Ohm to ground. I start disconnecting all ribbons from logic board one by one and when I disconnect ribbon between LOGIC and X-BOARD, shorcircuit disapppears.

    I remove X-board and all the semiconductors in the heatsink have all leads shorted to GND. It seems my repair didn't work...

    So, this is my plan, and I would like to hear if this sounds reasonable:

    -I have ordered a spare X-Board on ebay (fully checking all markings, 100% exact)

    -Instead of getting a new LOGIC board, I'm planning on piggybacking a 5Amp fuse onto the SMD fuse on Logic board, assuming nothing else is blown in the logic board so maybe I can save myself the money to get a full board.

    Do you think this all makes sense??

    Thanks in advance!!

    #2
    Re: Help repairing Samsung ps50c450

    I would replace the bad X-Main Bd when the other one arrives, leaving out the 5Amp fuse on the Logic Bd. Plug in TV and try a start-up. If No smoke or blown fuse is observed, measure if there is voltage on the connectors, shutdown and replace the 5Amp fuse. Try a start-up again and observe.

    Comment


      #3
      Re: Help repairing Samsung ps50c450

      Sounds like a plan, but Im unsure whether the high voltages will be present while the logic board fuse is out. Isnt the logic board the one which demands the Vs, Vg...from the PS?
      Thanks

      Comment


        #4
        Re: Help repairing Samsung ps50c450

        Yes but we are taking one small step at a time to reach our final destination. Before applying ac power, measure that ground fault on the one end of the 5amp fuse and see if it still exists or vanished with everything connected.

        Comment


          #5
          Re: Help repairing Samsung ps50c450

          Got you now...yes that makes sense
          Tnx

          Comment


            #6
            Re: Help repairing Samsung ps50c450

            Ok some updates here.
            The X-Board arrived today. Broken. Yes, a big chunk in the corner was smashed. Good thing it only affected 3 real traces so glueing it back and resoldering the traces was quick.
            I put it back in place. It all seemed good. Soldered a glass 5A fuse to the logic card (see previous posts)

            Turned on. Didn't want, on/off cycling.
            Started disconnecting cables from pairs of boards.

            Problem improved (by "improve" I mean I get to hear the Samsung startup tune and it won't shutdown) when I disconnected ribbon from LOGIC to X-BOARD. Was X-board bad again?

            Wait, it only improves when I disconnect that cable from the logic board side, it is still bad when I disconnect it from the X-board side!!(attached photo of boards without this cable) So the issue is not in the board, it is the cable now!

            Yes I take the LOGIC->X Board flat ribbon cable out and inspect it. Traces 2&3 are shorted. See attached photo, you can see the plastic is slightly melted in that area.

            So I'm ordering now this cable (hopefully it's as easy to find online as the boards are!) and see what happens next...

            Thanks everyone for being there
            Eduardo
            Attached Files

            Comment


              #7
              Re: Help repairing Samsung ps50c450

              ...so far it looks like locating a replacement for this flex cable is not going to be so easy...neither cheap..
              Anyone knows of any tip for this? I'm not paying $20 for a 1 ft cable to fix a tv that may still have other issues going on...
              Thanks in advance!!

              Comment


                #8
                Re: Help repairing Samsung ps50c450

                If only lines 2 and 3 are shorted, use a knife and cut between the traces where it is shorted, then put some tape between the traces to isolate them. This should get it working for doing the rest of the testing, once the set is fixed, order a cable. or check with a repair shop, they usually don't keep them.
                Last edited by R_J; 04-12-2018, 05:55 PM.

                Comment


                  #9
                  Re: Help repairing Samsung ps50c450

                  Too late for a repair for mine...I already cut it into two, expecting one half to be enough to reach between two boards going more straight. Not only no half was able to reach the length, also the short is present along the whole lenght of the cable, so in both halves.
                  Im in touch with a user on ebay who is selling a set of 3 LVDS cables for this TV to see if he can sell only one and get a better shipping cost
                  Thanks!

                  Comment


                    #10
                    Re: Help repairing Samsung ps50c450

                    Good to hear you are reaching nearer to solving your TV issue.

                    Comment


                      #11
                      Re: Help repairing Samsung ps50c450

                      Thanks Andrew, although I'm pretty stuck right now due to this flex cable...
                      Will keep posting updates here

                      Comment


                        #12
                        Re: Help repairing Samsung ps50c450

                        Ok this is hopefully the last update on this TV. I found a seller on ebay who had a post selling all the flex cables in this set. Talked hin into selling only the one I needed. He agreed. I received the needed flex cable 1 wk ago, tested it on the TV today and voila!! It works!
                        All seems good, tuning went right, image looks right, stayed on for several hours with no issue so I call it GOOD. Puts out a lot of heat...thou...
                        We were used to 32" in a small living room...now 50"...my kids said it looks like a cinema LOL

                        So I just wanted to say everyone involved in this thread, THANK YOU!

                        Comment

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