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    #1

    Astar LTV-2001 flashes once, turns off

    Hi all

    We received the 20 inch Astar LTV-2001 with the complaint that it comes on blue with a 'channel number' on upper right and then goes out right away.

    The power supply box is putting out the regulated 12 volts... Inside the Tv itself on the power supply/control/signal board off of the DIN connector where the 12 external power comes into has a 8 volt regulated ic and that is putting out regulated 8 volts...

    I have checked many caps but because this is a double sided circuit board, I am reluctant to pull too many out if they are not visibly doming or shrinking the wrap...

    The single cap on the backlight inverter board is measuring right on.

    I have posted the pictures. The middle picture is the side with the power supply section as near as I can tell.... toward the middle in the back seems to be a beefier section of components which I assume is for the backlight...

    There appears to be no schematic available at this point in time....

    Any ideas...... I do not want to ruin the board with needless pulling of caps.

    Thank you for your time...

    Bill
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    #2
    Re: Astar LTV-2001 flashes once, turns off

    Originally posted by billansor View Post
    We received the 20 inch Astar LTV-2001 with the complaint that it comes on blue with a 'channel number' on upper right and then goes out right away.
    Never heard of Astar, but did you check the inverter transformer secondaries?
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      #3
      Re: Astar LTV-2001 flashes once, turns off

      No...

      Unless I have seen burned marks on those secondaries... There appears to be almost no consistency to checking these. They both check at 320 ohms...

      The fuse on the inverter board also checks good

      Comment

        #4
        Re: Astar LTV-2001 flashes once, turns off

        I suggest localizing the problem. The approach I favor is to hook up a video source to the video and sound inputs (an old Nintendo to AV1 works fine) then stepping through the inputs. If at some point you can hear the sound, see if you can see the video by shining a flashlight on the screen. If you never hear the sound, you probably have a main board problem.

        Most of these have a number of LDO regulators in addition the the 8 Volt regulator you checked. Another thing to check is the voltage of the backlight control pin. Typically this will be at 3 volts or more when the backlights are on. If it goes high (> 3.0 volts), then drops down to near 0 V, the mainboard is shutting off the backlights. If it stays high, it's a problem with the inverter or the CCFLs.

        PlainBill
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

        Comment

          #5
          Re: Astar LTV-2001 flashes once, turns off

          If this lcd gets power from an outside power pack (12vdc) It could just be the wrong power pack.

          I power these up with a 12v fused battery. These inverters need about 1.5 to 2 amps to stay lit. If the power pack is bad or the wrong unit the backlight will come on then turn off and you would think it was a back light issue.

          I have seen this two times so far on the small tv/moniters.

          Comment

            #6
            Re: Astar LTV-2001 flashes once, turns off

            Hi

            An update... The set will not turn on now. I still have my 12 volt supply and the 8 volt regulator is still 8 volts. I checked for other ldo's and it seems like it is the 8 volt is the only one.

            The external power supply unit is the correct one..

            I am going to see if I can find a main board and go from there... However, it seems like those are going to be near impossible to find..

            I will keep updating as progress continues..

            Bill

            Comment

              #7
              Re: Astar LTV-2001 flashes once, turns off

              Originally posted by billansor View Post
              Hi

              An update... The set will not turn on now. I still have my 12 volt supply and the 8 volt regulator is still 8 volts. I checked for other ldo's and it seems like it is the 8 volt is the only one.

              The external power supply unit is the correct one..

              I am going to see if I can find a main board and go from there... However, it seems like those are going to be near impossible to find..

              I will keep updating as progress continues..

              Bill
              This is similar to one I'm fighting right now. It's a Samsung SyncMaster 170MP. The symptom was a clicking sound from the speakers - about once a second. This uses a 12V external adapter. Checking the 5V bus I saw pulses at the same rate. Then checking the 3.3V bus (derived from the 12V input), I saw the same pulses; it turned out they were on the 12V input.
              Yet the power brick checks out at full load, and checking the ESR of the caps (in circuit) doesn't show a problem. But with a more robust power brick it works fine.

              I would REALLY suggest trying an external supply capable of high current output. It would have saved me a lot of grief if I had done that.

              PlainBill
              For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

              Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

              Comment

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