Sony KDL46XBR10, Sony KDL52XBR10 LCD TVs – how to troubleshoot backlight problems – 6 blinks – shutdown
Sony XBR-10 series LED LCD TVs - Back-light troubleshooting - with, 6 blinks-shutdown or No shutdown
Super Slim DesignThe use of LED’s along the bottom edge of the LCD panel along with new circuit board designs and mounting allows for the creation of an exceptionally slim television. The depth of the panel varies from 15.8mm (0.622”) at the top, 40.3mm (1.59”) at the rear cover and 57.3mm (2.26”) at the bottom where the speakers are housed.
Edge LED Back-lighting
High-intensity LED’s strategically placed along the bottom edge of the LCD panel along and a wave guide diffuser plate that disperses the light to allow for a dramatic reduction of the depth of the television.
Troubleshooting
Power supply failures occurring in the media receiver or monitor will provide a diagnostics code via the POWER/STBY LED on the affected device. In situations where a complete power supply failure occurs there will not be a diagnostics indicator
LED Back-light Drive
The LED back-light power supply located on the GD1 board is shown. IC6700 contains the oscillator and drive circuits for the switching transistors Q6706 and Q6707. The PFC 390V source provides drive voltage to the switching circuit. T6700 and T6701 form a dual output switching supply.
One common phase output from each transformer is tied together to form a single positive voltage. The remaining outputs are used to provide 2 negative voltage sources which are split to provide 2 sources each for a total of 4 negative supply voltages. 4 groups of series connected LED back-lights are driven from the positive side by the common +OUT voltage. Each of the 4 groups is driven by an individual –OUT voltage. The common +OUT voltage is fixed at approximately +49VDC referenced to chassis ground. The -OUT voltage level varies depending on the back-light level setting in the customer menu. The level of this voltage is controlled by the PWM_DIMMER line entering at CN6253 pin 9. The activity of this PWM line can be read with a DVM. The DC voltage level varies from approximately 2.7V at maximum back-light down to 0.34V at minimum back-light. The voltage range of the –OUT lines (referenced to chassis ground) is approximately -22VDC at minimum back-light to -45VDC at maximum level.
An additional dimming control source is available at pin 6 of CN6253. This is a DC dimming control and is primarily affected by the dynamic back-light control circuits which are monitoring relative video level of the displayed picture. The DC voltage at this line varies from 2.8V at maximum
brightness to 0.96V at minimum.
The LED back-light power supply located on the GD1 board is shown. IC6700 contains the oscillator and drive circuits for the switching transistors Q6706 and Q6707. The PFC 390V source provides drive voltage to the switching circuit. T6700 and T6701 form a dual output switching supply.
One common phase output from each transformer is tied together to form a single positive voltage. The remaining outputs are used to provide 2 negative voltage sources which are split to provide 2 sources each for a total of 4 negative supply voltages. 4 groups of series connected LED back-lights are driven from the positive side by the common +OUT voltage. Each of the 4 groups is driven by an individual –OUT voltage. The common +OUT voltage is fixed at approximately +49VDC referenced to chassis ground. The -OUT voltage level varies depending on the back-light level setting in the customer menu. The level of this voltage is controlled by the PWM_DIMMER line entering at CN6253 pin 9. The activity of this PWM line can be read with a DVM. The DC voltage level varies from approximately 2.7V at maximum back-light down to 0.34V at minimum back-light. The voltage range of the –OUT lines (referenced to chassis ground) is approximately -22VDC at minimum back-light to -45VDC at maximum level.
An additional dimming control source is available at pin 6 of CN6253. This is a DC dimming control and is primarily affected by the dynamic back-light control circuits which are monitoring relative video level of the displayed picture. The DC voltage at this line varies from 2.8V at maximum
brightness to 0.96V at minimum.
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 back-light LED’s in one of the series strings
* Missing back-light on command.
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 back-light LED’s in one of the series strings
* Missing back-light on command.
Back-light
Troubleshooting
Troubleshooting back-light failures is relatively straight forward for this design. The PFC voltage generated on the same GD1 board must be present. The back-light 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 back-light groups. The back-light troubleshooting flowchart in Figure will assist in locating the cause of back-light issues.
With 6X Shutdown
In most cases, a fault occurring in the back-light circuits will cause a shutdown with a 6 blink error code. Determining the reason for the shutdown involves viewing the screen for any back light activity. The unit will generate 3 attempts to achieve successful back-lighting.
If no evidence of back-lighting appears on the screen, it can be assumed the inverter circuit is not starting. Verify the back-light on command is going high during the 3 attempts. If it is, the fault lies on the GD1 board. If the back-light 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 back-light. on command does not go high, the back-lights will not light and the unit will not shut down. A failure outside of the GD1 board is suspect.
If the back-lights 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 back-lighting on ¼ of the screen. This symptom is quite easy to see as the unit will make 3 attempts before shutting down.
Troubleshooting back-light failures is relatively straight forward for this design. The PFC voltage generated on the same GD1 board must be present. The back-light 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 back-light groups. The back-light troubleshooting flowchart in Figure will assist in locating the cause of back-light issues.
With 6X Shutdown
In most cases, a fault occurring in the back-light circuits will cause a shutdown with a 6 blink error code. Determining the reason for the shutdown involves viewing the screen for any back light activity. The unit will generate 3 attempts to achieve successful back-lighting.
If no evidence of back-lighting appears on the screen, it can be assumed the inverter circuit is not starting. Verify the back-light on command is going high during the 3 attempts. If it is, the fault lies on the GD1 board. If the back-light 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 back-light. on command does not go high, the back-lights will not light and the unit will not shut down. A failure outside of the GD1 board is suspect.
If the back-lights 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 back-lighting 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 back-lights but does not shut down, the GD1
board is the least likely component. If the DC or PWM dimmer lines fall
to zero, the back-lights will not turn on. This is also true for the back-light on command. A back-light 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