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Samsung SyncMaster 943NW partially fixed, trying for 100%

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    #1

    Samsung SyncMaster 943NW partially fixed, trying for 100%

    Hey, I bought this Samsung SyncMaster 943NW 20" monitor in a flea market for 10EUR.
    I was pretty optimistic that it might work out of the trashcan.
    It did not.
    It would turn on and I could see the faintest flash of dark grey, while the power LED stayed blue or blinked when the VGA cable was unplugged.

    When I opened it up, I noticed a blown cap and I replaced most of them, except for the large 100μF 450V one. I did a few brief tests and it seemed to be working fine, so I closed it back and was filled with this warm feeling of accomplishment.

    Later, when I tried to use it for more than a few minutes, it went black. I turned it off and back on a few times and each time the time to black diminishes, down to a flash. If I turn it off for a few minutes and then back on, it stays on for longer.

    The picture is there when checked with a flashlight. Do you think it is worth changing the high voltage capacitor or could it be something else?

    Thanks in advance for your time!
    Tags: None
    #2
    Re: Samsung SyncMaster 943NW partially fixed, trying for 100%

    that's a classic symptom of worn out tubes or a bad invertor.
    check the back for a date - if it's more than 3 years old it's probably the tubes.

    Comment

      #3
      Re: Samsung SyncMaster 943NW partially fixed, trying for 100%

      Make two of these to test your inverter. You will have two of these connected to one set of the socket, another set of the socket will have the lamps from the LCD panel connected. If the lamps stay on, then you know that the lamps that are not connected are bad.
      https://www.badcaps.net/forum/showth...er+testing+cfl
      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

        #4
        Re: Samsung SyncMaster 943NW partially fixed, trying for 100%

        Thank you both so much for your answers!

        Now, I just need to find some spare time to test the inverter and tubes. I will post the results and some pictures.

        Comment

          #5
          Re: Samsung SyncMaster 943NW partially fixed, trying for 100%

          I finally got around to fixing my monitor, after a couple of months, so I thought I would post an update on this thread.

          Thanks to the insightful advice I received here, I confirmed that there was indeed a problem with the inverter. The tubes did not look fresh either. Replacing either or both looked like a lot of work for me and possibly a technical challenge.

          So I had an epiphany. What if I replaced the CCFLs with LED strips. After all, they are there to light the LCD panel and LEDs do a pretty good job at lighting.

          After looking around, I found out I was obviously not the first one to come up with that idea. I watched a couple of nice videos, got a cool white LED strip, took apart the whole screen and started testing.

          Everything looked fine and I am now at a point where the monitor works just fine with its newfound light source. Due to lack of time, I just replaced the CCFLs with LEDs and kept the whole plexiglass & filters configuration. I experimented with plain LEDs behind the LCD panel and filters, but light did not seem to be evenly distributed. There would also be some practical challenges with filling the rest of the metal casing and not enough time to troubleshoot.

          It worked! So it is a success as far as having a working monitor, but there are still a few kinks to iron out.

          -The LEDs are powered by an external 12v power supply and there is a cable coming out the back connected with croc clips. I just need to drill a hole in the casing and attach a female connector. including the power supply in the box seems like an unnecessary trouble for a monitor that will not move once installed.

          -The LED strip is either on or off, independently so from the rest of the monitor. I need to add a switch that is triggered by the monitor's on/off button.

          -When the LED is on and the monitor switches modes, the screen displays white light, as there is no trigger to set it off and on. The same thing happens when the monitor goes into standby mode.
          From what I can see on the power supply board, the cables connecting it to the VGA controller include a "BD M", "AD M" and "SW". I am guessing SW should be 'switch', so this may work for the on/off as well. Trial and error (on a test LED) will tell.

          Well, there you have it! This project has been fun and very educating for me. The total cost for a working Samsung SyncMaster 943NW was ~15 EUR.

          Thanks again for all your help! Now that I got bit by the TV/monitor repair bug, I suspect I will be visiting the forum again soon ;-)

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