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    Samsung PN60F8500AFXZA, can't determine X or Y failure

    Hi guys!

    This plasma comes on and has no picture (can't see panel prime, but it may?)

    VS and VA shutdown immediately, but VSC stays up, even though it is -204v instead of -198v.

    When I disconnect the Y and X separately or together, the VA and VS still shut down at turn on. I think it's due to the type of ground detect circuit the power supply has, right? So it's not easy to just unplug a board to see what is causing the shut down.

    The main board has the logic built in and there is an led flashing once every (I think it was 2.5 seconds?) which the service manual says is a "X/Y drive failure".

    The question is: which one is it?

    I've tried unplugging the Y buffers from the panel and the VS and VA DO NOT shut down, but I don't see any panel breaks and I doubt the panel is bad. If I plug those back in and unplug the X side from the panel, I also stop the VS and VA from shutting down, but I think in both cases, it's just because the panel isn't being used that the voltages stop shutting down.

    I haven't tried testing the buffers for shorts, do you think I should? It just doesn't seem like they would be causing the issue if unplugging the Y board doesn't stop shut down.

    The power supply doesn't seem to have any of the usual bad connections.

    #2
    Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

    Here are the pictures.
    Attached Files

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      #3
      Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

      Your x is bad. If you are buffer board was bad you would probably not have VSCAN. The main kicker is when your x board is disconnected your VS comes back alive. If you're in question check the X board for any shorted mosfet transistors.
      Last edited by freakaftr8; 01-12-2018, 06:11 PM.
      Did I leave the soldering iron on?

      Comment


        #4
        Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

        Originally posted by freakaftr8 View Post
        Your x is bad. If you are buffer board was bad you would probably not have VSCAN. The main kicker is when your x board is disconnected your VS comes back alive. If you're in question check the X board for any shorted mosfet transistors.
        Thanks! I will check and see if there are any shorted. It's odd that the Y buffers being disconnected also stops the VS and VA from dropping, though, but aren't the X-Main and Y-Main panel connections linked in different ways, so maybe that's why? I will get back you on the tests next week.

        Comment


          #5
          Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

          I suppose it could be y buffer only if when you disconnect x, are you also disconnecting the ribbon cable that goes to the logic board?
          Did I leave the soldering iron on?

          Comment


            #6
            Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

            Originally posted by freakaftr8 View Post
            I suppose it could be y buffer only if when you disconnect x, are you also disconnecting the ribbon cable that goes to the logic board?
            No, I'm always leaving that plugged in.

            Comment


              #7
              Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

              Okay, I pulled the X-Main and tested all the parts on the heatsinks and found no low resistance readings. Everything is measuring at least 2k and up. What would you suggest? Maybe I should pull the Y-Main and do the same thing? And might as well pull the Y-Buffers and test for shorts as well?

              Comment


                #8
                Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                Yes check over buffer board. I didn't get an answer to if you have VSCAN or not.
                Did I leave the soldering iron on?

                Comment


                  #9
                  Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                  Originally posted by freakaftr8 View Post
                  Your x is bad. If you are buffer board was bad you would probably not have VSCAN. The main kicker is when your x board is disconnected your VS comes back alive. If you're in question check the X board for any shorted mosfet transistors.
                  Is VSCAN the same as VSC? If so, my original post says I have VSC at -204v (when it should be -198v) and it doesn't drop when the VS and VA drop at turn on.

                  Comment


                    #10
                    Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                    Did you get my previous post, Freakaftr8? About the VSC? Also, I just pulled the and tested the Y-Main and upper and lower buffer board and couldn't find any shorts on any of those boards, either. Ideas?

                    Comment


                      #11
                      Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                      Yes. Sounds like vscan is good then. So just to recap, unplug panel either at X or Y, all voltages stay up including VSC?
                      Did I leave the soldering iron on?

                      Comment


                        #12
                        Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                        Try this, pull the panel ribbons from the Y Buffer board but leave the buffer board connected to the Y sustain. Make sure X is all connected like normal. What happens?
                        Did I leave the soldering iron on?

                        Comment


                          #13
                          Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                          Originally posted by freakaftr8 View Post
                          Try this, pull the panel ribbons from the Y Buffer board but leave the buffer board connected to the Y sustain. Make sure X is all connected like normal. What happens?
                          I will try that and get back to you and yes, your recap of symtpom is correct.

                          Comment


                            #14
                            Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                            Originally posted by freakaftr8 View Post
                            Try this, pull the panel ribbons from the Y Buffer board but leave the buffer board connected to the Y sustain. Make sure X is all connected like normal. What happens?
                            Wait. That is what I already did originally. Remember? If I do that, the voltages stay up.

                            Comment


                              #15
                              Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                              This TV is known for the following failures. Power supply most common, Main board second most common, and Y-sustain as third most common.
                              In order to check the power supply. Disconnect everything from it, Short PS-on to ground and VS on to standby and check all output voltage. If all is correct then you have a good power supply. I would still check all transistors on heat-sinks for cracked solder joints however. That is common for this power supply
                              Now that we got that board out of the way, plug everything back in, and now lets move onto the Y-sus.
                              Disconnect the ribbon going between the Y-sus and the main board. Now turn the TV back on and check your VS voltage. Is it staying steady or is it still dropping down. If its still dropping back down then you have a bad main board. If it stays steady then you have a bad y-sustain.

                              Source:
                              Our company offers a repair service on all three of those boards, and this is how we tell our customers to determine which board is faulty in there set. Although we almost always suggest re-flowing the power supply if a Y-sus or main is found to be faulty, as that board does go out often.

                              Good luck

                              Comment


                                #16
                                Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                                Is there a subtle buzz to the panel when you have the sustain boards connected before everything shuts down? Turn off the lights in a dark Room and turn the TV on see if the panel attempts to glow before shutting down
                                Did I leave the soldering iron on?

                                Comment


                                  #17
                                  Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                                  Originally posted by Nick's Tvs View Post
                                  This TV is known for the following failures. Power supply most common, Main board second most common, and Y-sustain as third most common.
                                  In order to check the power supply. Disconnect everything from it, Short PS-on to ground and VS on to standby and check all output voltage. If all is correct then you have a good power supply. I would still check all transistors on heat-sinks for cracked solder joints however. That is common for this power supply
                                  Now that we got that board out of the way, plug everything back in, and now lets move onto the Y-sus.
                                  Disconnect the ribbon going between the Y-sus and the main board. Now turn the TV back on and check your VS voltage. Is it staying steady or is it still dropping down. If its still dropping back down then you have a bad main board. If it stays steady then you have a bad y-sustain.

                                  Source:
                                  Our company offers a repair service on all three of those boards, and this is how we tell our customers to determine which board is faulty in there set. Although we almost always suggest re-flowing the power supply if a Y-sus or main is found to be faulty, as that board does go out often.

                                  Good luck
                                  Thank you for your help. I followed your steps and found that the VS does not drop if the YSUS ribbon is unplugged from the main board. So I guess the YSUS is defective. And I had already checked the power supply for bad connections and found only slightly suspicious connections and resoldering them changed nothing. I will look into a replacement YSUS and/or look into your service.

                                  Comment


                                    #18
                                    Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                                    Originally posted by freakaftr8 View Post
                                    Is there a subtle buzz to the panel when you have the sustain boards connected before everything shuts down? Turn off the lights in a dark Room and turn the TV on see if the panel attempts to glow before shutting down
                                    No panel prime, but there is a brief buzz before it shuts down.

                                    Comment


                                      #19
                                      Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                                      Ok. As it sounds to me, (and I hope it's just YSUS faulty), sounds like your panel is damaged somehow.
                                      Did I leave the soldering iron on?

                                      Comment


                                        #20
                                        Re: Samsung PN60F8500AFXZA, can't determine X or Y failure

                                        You are getting shut down event if Vs and Va are good then die. Ctrl board switches them off to stop fire/electrocution in case of panel fault (crack, etc.) or failed sustain board.

                                        There are a number of things that can cause this.

                                        Usully the control board LED is blinking 5 seconds on 2 seconds off, which is DRV_RESET state, i.e. something is not right with something on the panel or controller boards and the control board has pulled the plug.

                                        If your LED is blinking once a second and STAYS blinking once a second, disregard this as your control board is running normally, and most likely it is main board that is bad and not sending video. You can try checking this by doing test pattern mode by jumpering pins 3-4 of the block on the control board.

                                        Your set has integrated control board, but the principle is similar, the hardware is copy-pasted onto the main board and behaves as a separate part essentially.

                                        Bad X or Y board - not shorted, but bad in some way.
                                        Bad buffer board shorting Vsch voltage and bringing -Vsc down with it.
                                        Bad panel, crack or lost gas.
                                        Bad control board firmware.

                                        You can rule out bad buffer board by checking for shorts.
                                        Similarly bad panel - check for cracks around the WHOLE panel.
                                        Bad control board firmware is rare. Often LED on control board will blink a pattern distinct from 5-2 bliks.

                                        If you have an oscilloscope, you can check the X/Y waveforms on power up, but if you are not familiar with what the waveforms should look like, you may be stuck here...So you would have to replace one of the two boards and see what happens.
                                        Last edited by tom66; 01-19-2018, 06:25 PM.
                                        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                                        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

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