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problem with samsung syncmaster 720V when insert vga cable

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    #1

    problem with samsung syncmaster 720V when insert vga cable

    Hi
    I found this lcd monitor and i'm trying to get it work
    First of all i tested it: with only the power cable inserted, the monitor works well, displaying "no signal" etc.
    When i connect vga cable to the monitor to testing the signal, lamps turn off and sometimes the power led starts to blinking.

    I opened the monitor. No visible damage to the components or bad smell or burns.
    I measured the voltage without signal cable. 5V and 12V are stable.
    When i connect vga, lamps turn of, sometimes blinking, and i hear a little medium frequency whistle by the PSU. Voltages become instable on the 12V if i measured it well (+11/+13V).

    So... are the capacitors damaged?


    Any suggestion?

    Thx for attention
    sorry for bad english
    Tags: None
    #2
    Re: problem with samsung syncmaster 720V when insert vga cable

    The standard procedure here is to post clear focused pictures of all your boards using the manage attachments functions so the pictures are attached to this forum. Please do not post inline because it slows down the loading of pages.

    After you have posted the pictures using manage attachments, we can suggest test points.
    --- begin sig file ---

    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

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    Comment

      #3
      Re: problem with samsung syncmaster 720V when insert vga cable

      I had a Samsung Sinkmaster with the same issue.

      With no video connected got the backlight and no signal display but when I plugged the VGA cable in. It acted as if it was in standby (amber light) and the backlights shut off.

      This is an issue on the VGA signal board I swapped it out with a new one and it was fixed. If the supply voltage on the board is good and the caps are good.

      Then it's probably either the video processing IC or a corrupted EEPROM neither of which you can replace because they're application specific and usually not available.
      Last edited by Krankshaft; 05-19-2011, 12:27 AM.
      Elements of the past and the future combining to make something not quite as good as either.

      Comment

        #4
        Re: problem with samsung syncmaster 720V when insert vga cable

        Thanks both for reply.

        Originally posted by Krankshaft View Post
        I had a Samsung Sinkmaster with the same issue.

        With no video connected got the backlight and no signal display but when I plugged the VGA cable in. It acted as if it was in standby (amber light) and the backlights shut off.

        This is an issue on the VGA signal board I swapped it out with a new one and it was fixed. If the supply voltage on the board is good and the caps are good.

        Then it's probably either the video processing IC or a corrupted EEPROM neither of which you can replace because they're application specific and usually not available.
        If the problem is the logic unit i can throw away this monitor lol... i hope the problem is on the PSU but i'm not sure obliuvsly... but i hear a whistle coming from the psu when the problem appears.

        @retiredcaps: ok but at this moment i dont have cams. i can shoot a photo with mobile phone but the quality will be bad...
        I will try it

        Comment

          #5
          Re: problem with samsung syncmaster 720V when insert vga cable

          The whistling is normal when the monitors in standby mode and the PSU isn't heavily loaded.
          Elements of the past and the future combining to make something not quite as good as either.

          Comment

            #6
            Re: problem with samsung syncmaster 720V when insert vga cable

            Originally posted by Krankshaft View Post
            The whistling is normal when the monitors in standby mode and the PSU isn't heavily loaded.
            damn i think you are right...
            i did further test:
            the whistle starts only when lamps turn off and stops when lamps turn on... maybe the problem isnt the capacitors...

            When i insert vga, lamps always turn off and sometimes (not always) power led starts to blikining...

            Comment

              #7
              Re: problem with samsung syncmaster 720V when insert vga cable

              Try checking the voltage regulator(s) on the logic board for proper output voltage.

              Comment

                #8
                Re: problem with samsung syncmaster 720V when insert vga cable

                Originally posted by jetadm123 View Post
                Try checking the voltage regulator(s) on the logic board for proper output voltage.
                are there voltage regulators on the logic board? it's better if i get the photo... tomorrow i will try.
                The PSU powers logic board with +12 and +5V

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