Replacing the defective circuit board assembly repairs
failures occurring in the LCD panel. This manual provides information to assist
in isolating which board may be the cause. The optimal goal will be to try to determine
which board to order before performing the service call based on customer
descriptions by symptom or self-diagnostics error code indications.
Any failure of the fluorescent back-lights or inverter
circuits will require the replacement of the entire LCD panel.
Video Failures.
Isolating a video failure can be tricky since the circuits
processing the video are located in the media receiver and the display panel.
Checking for the presence of audio is helpful since it will determine what
circuits to check. If audio is also missing, then something in common with both
is where you will want to check. Common circuits that can cause a “no audio or
video” symptom include the power supply lines or a failure of the HDCP key code
to “handshake” between the media receiver and the display panel. Observing the
Power/Standby LED on the media receiver and display panel for any blinking is
also useful. As an example: If the verification key for HDCP is not
communicated between the receiver and display panel, the power LED on the media
receiver will blink continuously for about 20 seconds before lighting a steady
green. It should normally blink 6 times and then remain steady.
Another useful feature to isolate video problems is the OSD.
This is generated in the media receiver by System Micro IC4410 located on the
M board. If the customer menu can be displayed without
distortion, the display panel is OK since the OSD is mixed with the active
video signal.
The media receiver
would need to be replaced in this situation.
The troubleshooting flowchart.
CLICK ON THE PICTURES TO ZOOM IN
LCD PANEL FAILURES
Once the video signal has been processed and sent to
the LCD panel, scan circuits use the video information to properly time the
lighting of each pixel. Any time a horizontal or vertical row of pixels is dark
or brightly lit, a panel failure is obvious. There may be single or multiple
lines of missing or lit pixels.
Typical LCD panel failure
Troubleshooting “No Power” Conditions.
Both the Media Receiver Unit and the LCD Display Panel
contain their own power supplies. Referring back to Figure 2-1 it is seen that
the media receiver creates its own power from the G board located inside the
unit. The display panel will have a G1 board for the 32” and a G2 board
if it is the 42” model. Determining which unit is the cause of a no power condition
is relatively easy by using the Power/Standby LED on either unit. The status of
the LEDs is able to tell if either unit is able to go into standby, power up,
or if there is a protect event occurring.
POWER/STANDBY LED INDICATION [ BLINKING CODES]
SELF DIAGNOSIS
The Power/Standby LED on the Media Receiver Unit and Display
Panel can provide valuable clues to where a failure may lie. Both units have their own protection circuits that are monitored by their
microprocessors. Power supply, fan
rotation, and temperature errors will cause the LED to flash red. The number
of times the LED flashes indicates the cause of the protection event. Whenever
a protect event occurs in the display panel, the media receiver will always flash 9 times, pause, and flash 9 times again.
