Cf1 Board; Troubleshooting Flowchart - Sony KDL70XBR7 Training Manual

CF1 Board

The microprocessor responsible for doubling the frame rate flashes a
green LED if it is functioning properly. Referring to Figure 2-3, the shield
of the CF1 board has been removed in order to clarify the location of the
heartbeat LED. Note there is another LED located in the extreme upper
right corner. This LED is always lit continuously. The green LED to the
left should be blinking at a rate of approximately once a second. If it is
not blinking, the failure can be assumed to reside on the CF1 board. This
board is considered part of the LCD panel and must be replaced as an
entire assembly along with the TCON board.
Video Distortion
This symptom can be rather subjective, especially if a customer is
attempting to describe it. Causes can range from a poor signal source,
failures in the video process circuits, or physical defects in the display
panel.
The best troubleshooting advice for video distortion is this: If the distortions
in the displayed picture are moving and not stationary, it is safe to assume
that the failure does not lie in the TCON or LCD panel. Although the video
process circuits can generate fixed distortions, the TCON and LCD panel
tend to generate symmetrical patterns. The LCD panel will usually have a
single line or a group of lines spaced evenly and they will be of the same
primary color.
Using the OSD graphics to help determine where a distortion is occurring
is the first step. Clean OSD graphics are a clear indicator of a good
TCON and LCD panel. If the OSD graphics are distorted, pay attention
to movement of the distortion and whether the distortion involves other
colors besides the primary red, green and blue. This is a clear indication
that the problem does not reside on the TCON or LCD panel.

Troubleshooting Flowchart

The troubleshooting flowchart in Figure 2-4 should provide some guidance
in isolating a failure involving the loss of video or distortions in the video.
CTV-53
Chapter 2 - Video Circuit Troubleshooting
BLINKING
HEARTBEAT
LED
FIGURE 2-2
HEARTBEAT LED ON FBU BOARD
HEARTBEAT LED
FIGURE 2-3
HEARTBEAT LED ON CF1 BOARD
STEADILY LIT LED
7