Aoc Lm729

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  • smason
    Badcaps Legend
    • Feb 2010
    • 1652
    • Canada
    #1

    Aoc Lm729

    Got an AOC LM729 today, friend of a friend's monitor.
    Symtoms are intermittent 3 seconds to black (not sure if image is on the monitor when black) and power led stays green. If powered off for a few hours it works again for a while.

    I didn't bother powering up, just disassembled.
    Someone has been in here before, a few caps have been replaced, and the inverter transformers, and AC power connector have been re-soldered.
    The circuit board is a bit warped as well.

    1 cap reads high esr (a 22uf @50v, circled in red) I don't have one, but may replace with a 47 @ 50v.

    One other obvious problem, (see second photo) an obvious bad solder joint on an inductor that may well explain the symptoms.
    Attached Files
    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....
    Tags: None
    • smason
      Badcaps Legend
      • Feb 2010
      • 1652
      • Canada
      #2
      Re: Aoc Lm729

      Resoldered the bad joint, replaced the 22@50 with a pair of 10@50 in parallel (Panasonic FM) and the montor is on test, so far so good.
      Out of circuit, the cap reads 18uf and 3.2 ohms ESR, may not have been an issue....
      Last edited by smason; 07-28-2010, 07:42 PM.
      36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

        Comment

        • meanderer
          Senior Member
          • Jul 2010
          • 50
          #3
          Re: Aoc Lm729

          Problem solved?

            Comment

            • retiredcaps
              Badcaps Legend
              • Apr 2010
              • 9271
              #4
              Re: Aoc Lm729

              Originally posted by smason
              Someone has been in here before, a few caps have been replaced, and the inverter transformers, and AC power connector have been re-soldered.

              One other obvious problem, (see second photo) an obvious bad solder joint on an inductor that may well explain the symptoms.
              The light blue cap is probably radio shack.

              What that is a very bad joint. Even my soldering skills are not that bad! :-)
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                Comment

                • smason
                  Badcaps Legend
                  • Feb 2010
                  • 1652
                  • Canada
                  #5
                  Re: Aoc Lm729

                  Originally posted by meanderer
                  Problem solved?
                  Still working this morning.
                  36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                    Comment

                    • smason
                      Badcaps Legend
                      • Feb 2010
                      • 1652
                      • Canada
                      #6
                      Re: Aoc Lm729

                      Originally posted by retiredcaps
                      The light blue cap is probably radio shack.

                      What that is a very bad joint. Even my soldering skills are not that bad! :-)
                      I forget now, but it looked like an OK cap, plus we don't have Radio Shack here (not that we don't have other crappy establishments that sell cheap GP caps) and it measured fine.

                      The solder joint was bad, but had no flux around it, so I don't think it was the last guy who worked on it. Likely a heat/cool/vibration issue.
                      As always, I dont just touch up bad joints, I remove all the solder and re-do them.
                      36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                        Comment

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