Sony KDL-32BX311 Service Manual ▷ View online
KDL-32BX311
16
SECTION 3 - CHASSIS OVERVIEW
COMPOSITE OR
COMPONENT 1
RF
COMPONENT 2
HDMI 1
PC HD15
POWER SUPPLY
SWITCH
UNIT
LED
IR RX
LCD PANEL
A
G13
H
L
R
ANALOG AUDIO OUT
OPTICAL AUDIO OUT
U3
MT5388
A/V DECODER
A/V PROCESS
CPU
TUNER
USB2.0
HDMI 2
LVDS
24V B+
AND CTL
AC IN
INVERTER
U8
CLASS D
AUDIO
AMP
FIGURE 3-2. BLOCK DIAGRAM
KDL-32BX311
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OVERVIEW
Most troubleshooting for this chassis focuses on the 3 major
components used:
•
The Main Board (A)
•
Power Supply Board (G13)
•
LCD Panel
This chapter provides practical troubleshooting procedures based
on the various symptoms that will appear when a particular circuit
fails to operate properly. Typical failure symptoms will be discussed
in this chapater with troubleshooting flowcharts for each symptom in
the
“Section 5 - Flow Charts and Diagrams” on page 26
.
UPDATING THE SOFTWARE
As mentioned in
“Section 2 - Software Requirements” on page
10
, there are several issues that may be resloved by updating
the software to the latest version. For a list of possible correctable
issues see
“Checking the Software Version” on page 11
.
SECTION 4 - TROUBLESHOOTING
VIDEO FAILURES
Problems that develop in the video circuits can appear as subtle or
major distortions, a loss of one or more colors, improper video level,
or a complete loss of video. When troubleshooting LCD display
devices the problem must be isolated to 2 major components: The
main board where the video processing is performed or the LCD
panel. In some cases the TCON may not be available as a separate
component and replacement of the LCD panel is required to rectify
a TCON problem.
Distortion in the video signal that affects all inputs can be challenging
Distortion in the video signal that affects all inputs can be challenging
at times since any of the above mentioned components can be the
cause. Fortunately, each of these components tends to generate
unique symptoms when a problem occurs. Some distortions may
occur that could be caused by either of these components but a
good understanding of the circuits and further investigation will
isolate the suspected circuit. The following sections will cover the
various scenarios of problems that may occur in the video processing
circuits.
NO VIDEO
A “no video” complaint can be caused by a number of reasons. The
first step is to determine if the condition is present from all input
sources. If any video source is working properly, the TCON (located
within the LCD panel) can be assumed to be OK. The backlights are
also functioning properly. Although it is unusual for a backlight failure
to cause a complete loss of video (the TV will shut down if a backlight
power or open LED is detected) there have been cases where the
backlights have failed to turn on without the unit shutting down.
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SECTION 4 - TROUBLESHOOTING
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
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
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.
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 27
should
provide assistance in isolating the cause of the video loss.
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
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
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
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SECTION 4 - TROUBLESHOOTING
TCON: Since the TCON allocates the RGB video information based
on specific timing information, the distortions tend to be fixed and
usually appears as symmetrical patterns that occupy most (or a
significant portion) of the display. The TCON circuits in this chassis
are integrated within the LCD panel which requires replacement of
the entire panel to remedy a TCON failure. Some examples of TCON
errors:
•
No video
•
Thin vertical lines spanning most or all of the display
•
More that one column of wide vertical columns which may
appear black or any color, or may contain distorted video.
•
Multi-colored vertical line patterns with a repetitive pattern
Service Tip: Whenever vertical lines of distortion appear, select an
inactive input or disconnect the antenna in the tuner mode. The idea
is to not have a high-definition signal as the source. This allows the
picture zoom functions to operate.
Change the zoom mode from the remote commander. If the lines
Change the zoom mode from the remote commander. If the lines
follow the normal and zoom modes the problem resides on the main
board. If the lines remain fixed throughout the various zoom modes
the TCON is at fault.
LCD Panel: Distortions originating from the LCD panel tend to be
LCD Panel: Distortions originating from the LCD panel tend to be
localized with the exception of horizontal line issues. A failure of a
gate driver can cause a horizontal distortion with all video content
below that point appearing distorted. Depending on which gate driver
has failed, the distortion may only cover a small area of the bottom of
the screen if the driver failed near the bottom of the panel, or a large
area of the screen if the driver failed near the top of the panel. With
the exception of visible physical damage, the following are some
examples of LCD panel related distortions:
•
Any single, thin vertical line (regardless of color)
•
Any thin vertical lines isolated to a specific area of the screen
•
A singe vertical column of lines of any color or containing
distorted video
•
Any fixed horizontal lines
•
Blotches of black or improperly colored areas
•
Ghosting of images in which the entire image is repeated one
or more times
A thorough understanding of how the video is processed throughout
the chain of circuits all the way to the panel is important. A past
article written for the Sony Newsletter described, in detail, how this
process works.
“Figure 5-2. Video Distortion Flowchart” on page 27
will assist in
isolating which component is causing the distortion.
AUDIO TROUBLESHOOTING
Since all audio signals are input, processed and amplified by the
main board, any issue involving the loss of audio or audio distortions
which are present at all inputs would dictate that the issue can be
resolved by replacing the main board. It is possible that a software
update might also resolve the issue, but it is very unusual for a
software update to affect all sources.
Audio problems that are input specific (especially the HDMI and
Audio problems that are input specific (especially the HDMI and
digital sources such as the USB input and tuner) are more likely to
point to the need for a software update and this is especially true if
the problem is intermittent.
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