Backlight Troubleshooting; With 6X Shutdown; With No Shutdown - Sony KDL46XBR10 Training Manual

Protection
The television will shut down and display a 6 blink error code on the
POWER/STBY LED if the following faults occur:
• Loss of PFC390 to the switching transistors (this is independently
fused by R6705.
• A fault in the switching supply causing it to not turn on.
• A loss of output from one or more of the –OUT lines.
• A failure of one or more backlight LED's in one of the series
strings
• Missing backlight on command.

Backlight Troubleshooting

Troubleshooting backlight failures is relatively straight forward for this
design. The PFC voltage generated on the same GD1 board must be
present. The backlight on command at pin 8 of CN6253 must go high
(approx. 3.3V). The PWM and DC dimmer lines must not be zero. If all
of the above criteria are met, power will be applied to the LED backlight
groups. The backlight troubleshooting flowchart in Figure 6-5 will assist in
locating the cause of backlight issues.

With 6X Shutdown

In most cases, a fault occurring in the backlight circuits will cause a
shutdown with a 6 blink error code. Determining the reason for the
shutdown involves viewing the screen for any backlight activity. The unit
will generate 3 attempts to achieve successful backlighting.
If no evidence of backlighting appears on the screen, it can be assumed
the inverter circuit is not starting. Verify the backlight on command is going
high during the 3 attempts. If it is, the fault lies on the GD1 board. If the
backlight on command does not go high, look for an open connection
between the QTM and GD1 board or replace the QTM board. This
symptom is very unusual to encounter. In most cases where the backlight
CTV-62
Chapter 6 - Power Supplies and Protection
on command does not go high, the backlights will not light and the unit will
not shut down. A failure outside of the GD1 board is suspect
If the backlights light evenly across the screen, the inverter circuit is likely
shutting down due to excessive voltage or current conditions. This would
require replacement of the GD1 board.
If one of the LED's in the 4 groups fails, the unit will shut down with a 6X
error. This condition will appear on the screen as a large vertical band of
no backlighting on ¼ of the screen. This symptom is quite easy to see as
the unit will make 3 attempts before shutting down.

With No Shutdown

If the unit turns on with no backlights but does not shut down, the GD1
board is the least likely component. If the DC or PWM dimmer lines fall to
zero, the backlights will not turn on. This is also true for the backlight on
command. A backlight command that does not go high is usually caused
by a "hung" microprocessor which has stopped during the boot routine.
Loss of PWM dimmer signal is a fault with the microprocessor. A loss of
the DC dimmer voltage usually indicates a defective TCON. Fortunately,
all of these circuits are located on the QTM board and should be remedied
by the replacement of this component.
39