Announcement

Collapse
No announcement yet.

LG 42" Plasma Display Model 42PT350R

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    LG 42" Plasma Display Model 42PT350R

    Hello Guys,

    I am not familiar at all with plasma tv's but i tried my luck anyway since business is so bad. We gotta try, right?
    Anyway, the original problem was a tv clicking and not starting due to a short circuit on the Z-Sustain board (on the right side from the rear).
    I found two transistors shorted (30F123) and changed the gate driver ic's as well. I think they were FAN73711. I soldered for dry joint on power supply, Y-Sustain and Z-sustain. Started up the TV and the short was gone so i had an image but.....
    Lots of colorful speckles on the image and also there seems to be "mal discharge". I keep seeing the previous image on the new image.
    I had color bars been generated via my color bar generator tester and when i went to a white image i could still see the bars bleeding through in the image.
    The white raster is also not right its more patchy and gray. Images to follow

    #2
    This is the board layout.
    Attached Files

    Comment


      #3
      Click image for larger version

Name:	Panel Voltages.jpg
Views:	124
Size:	2.09 MB
ID:	3264935 Close ups of boards
      Attached Files

      Comment


        #4
        Some pictures of the problem
        The white raster is gray and it has the color bars of the previous image
        Attached Files

        Comment


          #5
          I just don't know where to measure Vscan and what to use as ground reference. Is chassis ground ok?
          Vy is ok, Vs and Va is according to panel sticker, some other voltages on Y-SUS also ok according to panel sticker. I think it was a 200V and a 120V. I am at home now so i am recalling from memory. I do have an oscilloscope but don't know what to measure.
          on Y-SUS +5VF and +15VF measure weird with chassis ground as reference. its not 5V and 15V.
          I suspect something is wrong on this board, not sure.
          I did take oscillogram images of the waveform on the buffer board and it looks right, not sure what the peak voltages must be.
          Specific question might narrow this down.🤭

          Comment


            #6
            There was a +15V rail that measured 18.2V somewhere there.

            Comment

            Working...
            X