Announcement

Collapse
No announcement yet.

AOC LM2028 no function

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    AOC LM2028 no function

    Hi,
    my AOC LM2080 stoped working - no start up.
    no POWER LED, CCFL´s dont light up, nothing on display

    The power supply seems to be OK -> 5V and 12 V OK

    At the Collectors of the 4 big TRS on signal PCB i measure 2V5 and 3V3.
    The 24MHz and 14Mhz Oscillators are running,
    but there is no traffic on I2C-Bus.
    The 8bit Microcontroller from Winbond does not provide a cycle for I2C.

    Do someone have an idea?
    May somone have a schematic?

    Thanks

    Tom
    Tags: None
    #2
    Re: AOC LM2028 no function

    You'll need to post some photos of the entire power (top and bottom) and logic boards. Members need to see what you're seeing in order to help you.

    https://www.badcaps.net/forum/showthread.php?p=118105


    https://www.badcaps.net/forum/showthread.php?t=1868

    Comment

      #3
      Re: AOC LM2028 no function

      Here some Photos from Power supply and signal board
      Attached Files

      Comment

        #4
        Re: AOC LM2028 no function

        Originally posted by TFT-Tom View Post
        Here some Photos from Power supply and signal board
        Check the voltage regulators circled in yellow. The part numbers should give you a clue as to the expected output voltages. For example A1117-33 indicates 3.3V DC output.

        List and measure all 3 voltage regulators. List all voltages on all pins.
        Attached Files
        --- 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.

        --- end sig file ---

        Comment

          #5
          Re: AOC LM2028 no function

          Originally posted by TFT-Tom View Post
          Hi,
          my AOC LM2080 stoped working - no start up.
          no POWER LED, CCFL´s dont light up, nothing on display

          The power supply seems to be OK -> 5V and 12 V OK

          At the Collectors of the 4 big TRS on signal PCB i measure 2V5 and 3V3.
          The 24MHz and 14Mhz Oscillators are running,
          but there is no traffic on I2C-Bus.
          The 8bit Microcontroller from Winbond does not provide a cycle for I2C.

          Do someone have an idea?
          May somone have a schematic?

          Thanks

          Tom


          Hello Tom and welcome to the forum! When you say " At the Collectors of the 4 big TRS on signal PCB i measure 2V5 and 3V3", I assume you mean the voltage regs outputs at 2.5V and 3.3V on the logic card in photo #3 . Correct? Please supply the part number of each one, so that we can verify the proper output voltage.

          Comment

            #6
            Re: AOC LM2028 no function

            Originally posted by jetadm123 View Post
            When you say " At the Collectors of the 4 big TRS on signal PCB i measure 2V5 and 3V3", I assume you mean the voltage regs outputs at 2.5V and 3.3V on the logic card in photo #3 . Correct?
            Hmm, I didn't pickup on the 2V5 3V3 convention. I haven't seen that before, but it sounds those are working properly.
            --- 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.

            --- end sig file ---

            Comment

              #7
              Re: AOC LM2028 no function

              Originally posted by retiredcaps View Post
              Hmm, I didn't pickup on the 2V5 3V3 convention. I haven't seen that before, but it sounds those are working properly.
              Yes, his terminology also threw me for a loop.

              Comment

                #8
                Re: AOC LM2028 no function

                Hi,
                yes, 4 TRS = Voltage Regulators - sorry.
                By the way, sorry for my bad English too

                I read the voltage on the 4 regulators as follows:

                U10 Pin1: GND U11 Pin1: GND
                U10 Pin2: 2V50 U11 Pin2: 2V51
                U10 Pin3: 4V63 U11 Pin3: 4V61

                U10 / U11 - Low Drop Voltage Regulators RT9164 (2V5 / 1A)


                U9 Pin1: GND U12 Pin1: GND
                U9 Pin2: 3V31 U12 Pin2: 3V30
                U9 Pin3: 4V63 U12 Pin3: 4V61

                U9 / U12 - Low Drop Voltage Regulators AIC1084-33PE (3V3 / 5A)

                May be the Vin´s are a little low although the supply Voltage from PSU is 5V (12V) constant - I will look for it.

                The Signal Board does not take current on the 5V line but approx. 100ma on the 12V line (no matter of video signal).

                I still missing the µC´s clock Signal on PIN "ALE" (I²C Clock)
                It should be 1/6 of X2... -> µC (U402) dont start up (5V supply OK)

                Tom
                Attached Files

                Comment

                  #9
                  Re: AOC LM2028 no function

                  Originally posted by TFT-Tom View Post

                  By the way, sorry for my bad English too
                  Your english is fine. Better than some people who don't use any punctuation or treat this forum like twitter or some cell phone chat.

                  May be the Vin´s are a little low although the supply Voltage from PSU is 5V (12V) constant - I will look for it.
                  On the connector between the logic board and the power board, are you getting a solid 5V DC or 4.6V DC?

                  Excellent pic.
                  --- 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.

                  --- end sig file ---

                  Comment

                  Previous template Next
                  Working...
                  X