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Acer AL2416W backlight

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    Acer AL2416W backlight

    Hello!

    I know this is a common problem in this particular screen, but I have read all the threads about it but I still have the problem, where the backlight goes out after a few secs of working.

    I got the monitor from a friend, whose dad already messed with this monitor - well, everything was bad on it, since he knows nothing about electronics. The PSU caps were all replaced with general purpose ones, and the inverter mosfets were so badly soldered, that the legs were literally shorted on them. All the inverter caps were general purpose too. The fuses were bad (2 of the 3). Ofc the backlight didn't even try to turn on at this point.. so I started to work on it.

    So firstly, I replaced all the caps on the PSU with Low ESR ones.

    Then I moved to the inverter board, where I replaced the fuses with 3.15A ones, all the mosfets had to go too, so I replaced them with ones I found equivalent on alltransistors.com
    For testing, I kept the general caps on it, just to see if I can get something.

    Well, yes, I could get an Acer logo with backlight, for about 0.5secs max. I knew that I am making progress, so I ordered Low ESR caps from the only hungarian electronics shop that is fairly okayish..

    There should be 10x100uf 35V caps on the board, but since they didn't have them, I had to buy 2x220uf 35V for the voltage regulator area, and 2x470uf 35V for the mosfets area (so instead of 8x100uf its 2x470uf). I watched a youtube video where the guy did the same, and for him, it worked with only 4 caps on the board.. but just to have some spare, I ordered more.

    The caps arrived today, they turned out to be Samxon GF, which, on the shop was labeled as Low ESR caps. So i soldered them on the inverter, and yes, now the backlight is working for longer, like 1-2 secs, but definitely turns off after it and refuses to come back. The display is working however, I can see the picture if I use a flashlight.

    I was (I am) confused, so I installed the spare caps on the inverter too, all of them, even the 2200uf Teapo Low ESR ones I bought for another screen PSU, but still does the absolute same.. I can't seem to find what the problem is.

    Do you have any ideas?

    #2
    Re: Acer AL2416W backlight

    my guess is a faulty back light inverter transformer

    Comment


      #3
      Re: Acer AL2416W backlight

      How could I test if a transformer is dead? This is something I never did before.

      Comment


        #4
        Re: Acer AL2416W backlight

        It may not be really dead as an open winding, at least I haven’t come across one. First check the resistance of the secondary output side of each transformer and compare them to each other. They should run within 3%. Also look for burn or darkened circuit board underneath a transformer. A bad transformer runs hotter. Check for cracked solder joints and those blue little hv capacitors on the output of the inverter.

        Comment


          #5
          Re: Acer AL2416W backlight

          Attach good clear pictures of the boards will help.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment


            #6
            Re: Acer AL2416W backlight

            So I today replaced 2 of the caps to another brand, and cleaned the board, also resoldered all transformers, but nothing helped so far.

            I attach the best pictures I can.

            Important, that the discoloration of the board near the left side caps is because the poor quality flux my friend's dad used, and the misaligned mosfet is because he ripped some trace here and there, and the whole board was badly soldered with really poor quality solder, that I couldn't pick up with my wick.

            However, my soldered connections are allright, according to my multimeter.

            I noticed, that there is a pot at the connector. I don't know if he messed with that, but what should be the value?

            Also, for the cap replacement I got the idea from this: https://www.youtube.com/watch?v=y23kaa9v264

            EDIT: I was just wondering if I could use another 24" screen inverter (got it from a Samsung), since it has the same amount outputs, the connectors are the same, hell, even the 14 pin pinout is the same (only the last, 14th pin is "PWM" meanwhile the TDK has it as "NC".). This is the inverter I got the 3.15A fuses from, and it had rubycon caps which I could put back. (Picture included).
            Attached Files
            Last edited by dominik0801; 04-10-2020, 03:55 AM.

            Comment


              #7
              Re: Acer AL2416W backlight

              Well.. I did reassemble the samsung's inverter and put in the Acer, and the backlight works now.. Since the original board is badly messed by my friend's dad, I might rather use this, known good inverter. What do you think, could it work in a long term usage like this?

              Comment


                #8
                Re: Acer AL2416W backlight

                The inverter will work ok, there is not much difference between them.

                Comment

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