Video Distortion - Sony KDL-32BX320 Service Training Manual

If the loss of video occurs on all inputs, the problem will require
additional diagnostic work. The presence of audio is an important
sign to check for. Missing audio accompanying a loss of video helps
to eliminate the TCON as the cause and would point to the main
board as the culprit. If audio is present, the next step is to determine
if the video loss is occurring in the video process circuits on the main
board, or the LVDS cable link from the main board to the LCD panel.
Service Tip: If a service call is made for a "no video" complaint, a
warranty repair would require the technician to bring the main board
to the location. Install the main board and if the video problem is not
resloved it is safe to assume the problem might reside in the TCON.
If the TCON is not available as a replacement part, this issue would
require replacing the LCD panel.
HINT: One method to test a TCON, which works rather well in most
cases, is to remove the LVDS connector at the panel connection
while the TV is running. Be certain to release the lock tabs and
handle the connector carefully to avoid damage. If there is any tape
securing the cable to the panel near the input, temporarily remove
the tape to allow free movement of the cable.
Carefully insert and remove the connector while slightly rocking it.
Observe the screen as you do this. If any activity appears on the
screen (flashes, lines or patterns) The TCON is OK. The TV may shut
down within a 10 to 20 second period because the protect circuits
have detected a TCON failure. If this happens, simply re-insert the
LVDS connector, turn the TV back on, and try the procedure again.
Normally, you should be able to detect something on the screen
within a matter of seconds.
Figure 5-2. Video Distortion Flowchart on page 32
assistance in isolating the cause of the video loss.
KDL-32BX320/32BX321/32BX420/32BX421/40BX420/40BX421/46BX420/46BX421
SECTION 4 - TROUBLESHOOTING

VIDEO DISTORTION

This is, perhaps, the more difficult failure to diagnose. It is difficult
when talking to the customer on the phone because an accurate
description of the problem must be obtained in order to determine
which part (or parts) to bring to the location. It may also be difficult
for the technician when the problem is witnessed.
If the problem is specific to one or more inputs it should be easy to
determine if the fault lies on the main board or a device that is plugged
into it. If the distortion occurs at all inputs it must be analyzed based
on what appears on the display and isolated to the main board,
TCON, or LCD panel. These components usually cause distortions
that are unique to the specific circuit. Below is an example of the
typical distortions:
Main Board (A Board): Since the video signal is processed on
a frame-by-frame basis it is very unlikely that a distortion that is
occurring on a specific part of the display panel is originating here.
Distortion problems originating in the video process circuits tend to
affect the entire picture. The following are some examples:
• Improper color reproduction or no color
• Improper luminance levels
• Lack of detail in the picture
• Distortions that change with movement in the video
• Diagonal lines
• No video
should provide
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