SONY KDL22EX308 - KDL32EX308 Back-light Issues _ Check Points
KDL22EX308 - KDL32EX308 Back-light Issues _ Check Points - Sony LCD TVs.
BACK-LIGHT ISSUES
Under
normal circumstances, any failures in the back-lighting system will
cause the unit to shut down. If one or more of the
fluorescent back-lights fails to turn on, or if the high voltage
inverter circuit fails to turn on, the
unit will shut down and the standby LED will blink in groups of 6. The
first step to determine the cause of the
failure is to observe the screen of the television when it is first
turned on.
If the back-lights turn on before the shutdown, it is likely that one of
the
lamps has failed to turn on and the LCD panel must be replaced. If
the back-lights do not turn on, the high
voltage inverter did not start and, depending on the method of
generating high
voltage, replacement of the power supply or inverter board is necessary.
NO BACK-LIGHT_NO SHUT DOWN
It is possible for a symptom of no back-lighting to occur that does
not cause the television to go into protective shutdown. Dynamic dimming
control of the back-lights is performed by monitoring information from the TCON
board. This is in the form of data and determines the brightness level of the back-lights based on video content. If
the TCON fails to process the RGB video data, or if the dimmer data line fails,
the back-lights will not turn on. Audio will be present if the selected input
has it available. The television will remain on indefinitely with the green
Power LED lit. If the TCON is available, it can be replaced to resolve the
issue. If not, the LCD panel must be replaced.
Diagnostics History
Figure illustrates an example of the diagnostics history page. Entry to this page is achieved while the television is powered down and pressing the following buttons on the remote commander: “DISPLAY”, “5”, “VOL –“, “POWER”. This feature is useful for failures which are intermittent or when the customer is not sure what is causing the television to shut down sometimes. Once a corrective action is determined the error events should be cleared to zero. This is accomplished by pressing the “8” key followed by the “0” key on the remote commander.
Figure illustrates an example of the diagnostics history page. Entry to this page is achieved while the television is powered down and pressing the following buttons on the remote commander: “DISPLAY”, “5”, “VOL –“, “POWER”. This feature is useful for failures which are intermittent or when the customer is not sure what is causing the television to shut down sometimes. Once a corrective action is determined the error events should be cleared to zero. This is accomplished by pressing the “8” key followed by the “0” key on the remote commander.
The drawing in Figure contains the board-to-board connector and
pin information for the KDL22EX308 to identify voltages, signal and control
lines for
troubleshooting purposes. Figure illustrates the same information for
the
KDL32EX308. All critical voltages and control signals are
easily accessed at the power supply board. Use this drawing in
conjunction with the
previously discussed troubleshooting techniques and flowcharts
for testing operating voltages and control signals.
Figure illustrates the rear of a KDL22EX308 with the cover removed. The
location of the major circuit boards and
connectors for voltage checks is provided.
SONY KDL Series TVs.
KDL22EX308 TEST POINTS & BOARD LOCATIONS
KDL32EX308 TEST POINTS & BOARD LOCATIONS
