Display And Keypad Backlight Troubleshooting - Nokia 6275 Baseband Description And Troubleshooting

6275/6275i (RM-154)
Baseband Description and Troubleshooting

Display and Keypad Backlight Troubleshooting

The display backlight uses four LEDs in series powered by an external LED driver.
LED driver
LED driver
Dlight
enable
1. Perform a visual inspection of the LCD connector and the LED driver circuitry.
2. If the display backlight does not turn on, check VLED +(~17V) for the main
display.
• If the voltages in the previous step are present, assume the driver is working
properly and the LED inside the display might be bad. Replace the display.
• If not okay, check VLED+ and VLED- (LED return GND) on the display driver
circuitry.
3. If the keypad backlight is off while the display backlight is on, check the B2B
connection and the LED on the keypad.
4. Check that the Klight signal is high (~4V) to turn on the main LCD and keypad
LEDs. If not okay, check the UEMEK.
5. Check that the Vbat(~4V) and Vin(~4V) are present. If not, check the power
supply connection.
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Vout (~17V)
Vout (~17V)
Figure 33: Display Backlight test points
Company Confidential
Nokia Customer Care
Rset for internal display
Vbat
LED driver
Issue 1 - September 2006
VLED+
VLED_key