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    #41
    Re: LCD-TV repair

    Originally posted by PowerAmpFreak View Post
    Said and done, no improvment after changing the 680uF caps. This one is nagging me. One question, does the CCFL or EEFL lamps turn on directly after supplying HV to them? Or could it take a few seconds?
    It could take a few seconds especially if the lamps are old. Just like it happens with the ones used for house lighting.
    Originally posted by PeteS in CA
    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
    A working TV? How boring!

    Comment

      #42
      Re: LCD-TV repair

      Originally posted by Th3_uN1Qu3 View Post
      It could take a few seconds especially if the lamps are old. Just like it happens with the ones used for house lighting.
      Ok, then it's very strange that it shuts off already in two seconds. The lamps may haven't even come on after this short time. It must be something else the inverter senses that is out of limits.
      By following the traces from the HV inverter outputs I could see this was fed back to the inverter controller by some network. This could be the over voltage protection. Without the schematics this is going to be hard.
      Attached is a picture of the inverter board.
      Attached Files

      Comment

        #43
        Re: LCD-TV repair

        Don't you have a datasheet for the inverter controller? They are usually obtainable by a minute (or less) of googling.
        Originally posted by PeteS in CA
        Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
        A working TV? How boring!

        Comment

          #44
          Re: LCD-TV repair

          ..
          Attached Files

          Comment

            #45
            Re: LCD-TV repair

            Thanks guys, but of course I have the datasheet for the '9882 but no schematics of the inverter.

            Comment

              #46
              Re: LCD-TV repair

              There is no way to simulate the load of the lamps? Then the inverter board should remain on. Just an assumption mind you.

              Comment

                #47
                Re: LCD-TV repair

                Originally posted by Johnny P View Post
                There is no way to simulate the load of the lamps? Then the inverter board should remain on. Just an assumption mind you.
                It's a good idea, but the load of the lamps seems to be purely capacitive and I don't know if this actually could be substituted by a resistive load. But one thing I might try is to power up another backlight (on another tv) with this inverter and see what happens. Then I could swap it all around and power the problematic panel with a known good inverter.

                Comment

                  #48
                  Re: LCD-TV repair

                  Right, as long as the values are the same. What a PITA!

                  Comment

                    #49
                    Re: LCD-TV repair

                    Originally posted by Johnny P View Post
                    Right, as long as the values are the same. What a PITA!
                    PITA? Hmm...

                    Comment

                      #50
                      Re: LCD-TV repair

                      Pain in the ass.

                      Comment

                        #51
                        Re: LCD-TV repair

                        Originally posted by Johnny P View Post
                        Pain in the ass.
                        Hehe ... OK!
                        Yes - you're right, this has taken far too much time already

                        Comment

                          #52
                          Re: LCD-TV repair

                          I had failed ccfls on au-optronics panel (L/G) panel would light up for 2 seconds then shut down.
                          I first found a bad mosfet on slave inverter. and repaired that and it was working( the inverter).

                          The best thing I did is take another inverter board (one piece) powered off of 24vdc.

                          I knew it was good and the backlights did the same thing (2 seconds to black).

                          I then pulled the panel apart and found 3 bad ccfls.

                          Took them from another panel and soldered them in (some solder in and some push in).

                          Then I replaced them all (used) for color match.

                          Comment

                            #53
                            Re: LCD-TV repair

                            Originally posted by cadiman View Post
                            I had failed ccfls on au-optronics panel (L/G) panel would light up for 2 seconds then shut down.
                            I first found a bad mosfet on slave inverter. and repaired that and it was working( the inverter).

                            The best thing I did is take another inverter board (one piece) powered off of 24vdc.

                            I knew it was good and the backlights did the same thing (2 seconds to black).

                            I then pulled the panel apart and found 3 bad ccfls.

                            Took them from another panel and soldered them in (some solder in and some push in).

                            Then I replaced them all (used) for color match.
                            Yes, I had the TV all in pieces trying to get into the panel itself and look for bad CCFL's, but I was forced to stop when I found that Samsung used steel rivets to put the panel assembly together and that the panel could be bought as a complete module $$$$, so appearently this will be very hard to repair. I've confirmed that both HV outputs generate voltages about 2.5kV, so I can only see the panel as the problem right now.

                            Comment

                              #54
                              Re: LCD-TV repair

                              2.5kV is strike voltage, if that doesn't drop off at all before the inverter shuts down, then it's definitely failed CCFLs.
                              Originally posted by PeteS in CA
                              Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                              A working TV? How boring!

                              Comment

                                #55
                                Re: LCD-TV repair

                                Originally posted by Th3_uN1Qu3 View Post
                                2.5kV is strike voltage, if that doesn't drop off at all before the inverter shuts down, then it's definitely failed CCFLs.
                                I did the voltage measurements quick, since my oscilloscope probe is rated for 1500V peak but I was so curious so I give it a shot anyway.
                                I see no additional load on mains when inverter goes on, I would expect the power consumption to raise a bit if the CCFL were properly loading the inverter, but I cannot see this. Which also tells something is bad in the panel.
                                Is there any protection inside the panel, fuse or something that my go open if there's a CCFL failure?
                                It feels the HV goes into an open circuit.

                                Comment

                                  #56
                                  Re: LCD-TV repair

                                  Originally posted by PowerAmpFreak View Post
                                  Is there any protection inside the panel, fuse or something that my go open if there's a CCFL failure?
                                  No... but the wires going to the lamps can break, a few members here have found loose connections to otherwise good CCFLs.
                                  Originally posted by PeteS in CA
                                  Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                                  A working TV? How boring!

                                  Comment

                                    #57
                                    Re: LCD-TV repair

                                    Originally posted by Th3_uN1Qu3 View Post
                                    No... but the wires going to the lamps can break, a few members here have found loose connections to otherwise good CCFLs.
                                    Ok, you mean inside the panel or the wires from inverter to panel?

                                    Comment

                                      #58
                                      Re: LCD-TV repair

                                      Inside the panel, the connections to the lamps themselves.
                                      Originally posted by PeteS in CA
                                      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                                      A working TV? How boring!

                                      Comment

                                        #59
                                        Re: LCD-TV repair

                                        The panel has two HV wires, each on either side of the panel. I believe there are several CCFL or EEFL's connected in parallell, so why shouldn't a few light if one or more were bad? Or their wires were loose.
                                        It looks like one of the inputs has been disconnected so none of the lamps has contact with the HV supply.
                                        By the way, is it possible to make a capacitance measurement across the lamps?

                                        After the easter holiday I'll try to take some close pictures of the panel assembly and see if any of you might have a good idea how to get into the lamp compartment.
                                        Last edited by PowerAmpFreak; 04-23-2011, 12:14 PM.

                                        Comment

                                          #60
                                          Re: LCD-TV repair

                                          Originally posted by PowerAmpFreak View Post
                                          The panel has two HV wires, each on either side of the panel. I believe there are several CCFL or EEFL's connected in parallell, so why shouldn't a few light if one or more were bad? Or their wires were loose.
                                          It looks like one of the inputs has been disconnected so none of the lamps has contact with the HV supply.
                                          By the way, is it possible to make a capacitance measurement across the lamps?

                                          After the easter holiday I'll try to take some close pictures of the panel assembly and see if any of you might have a good idea how to get into the lamp compartment.
                                          Email ccflwarehouse and find out exactly what's inside your panel, then try to find similar CCFLs to substitute .They may be trying to light but you are unable to see them through the dark LCD panel
                                          Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                          Comment

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