Trouble Shooting Guide, Standard
4/00021-2/FEA 209 544/31 B
15(23)
Measure the voltages on the display pads (H623, Fig. 5.1).
If SDA or SCL voltage is missing, check the VDIG voltage (2.75V).
If the VDIG voltage is correct, measure the resistance of R619 (6.8 kohms), R620 (6.8
kohms), R615 (0 ohm) and R614 (0 ohm). Also measure the resistance of C670, C671, C672,
C673 and C674 (>1Mohm). If any of the resistances are incorrect, replace the corresponding
component.
If the fault remains, change the display.
5.4
Background illumination glows faintly or does not
work at all
Open the phone and check for liquid damage.
Clean X750 if needed.
Replace the illumination panel.
Power up the board and start it by pressing the On/Off key.
NOTE!
All measurements are done with the illumination on. The illumination is only lit
for about 25 seconds, press any key to light it up again.
Measure the voltage on pin 6 and 8 of N750 (26 V).
If the voltage is incorrect, measure the voltage on pin 10 (3.8 V), pin 5 (2.7 V), pin 2 (0.9 V)
and on pin 4 (1.4 V) of N750.
If the voltage on pin 10 (3.8 V) is incorrect, measure the resistance of L750 (23 ohms), C751
(>1 Mohm) and the resistance from L750 to VBATT (0 ohm).
If any of the L750 or C751 resistances are incorrect, replace the corresponding component.
If the resistance from L750 to VBATT is incorrect, the foil is damaged. Send the unit on
according to the local company directives.
If the voltage on pin 5 (2.7 V) is incorrect, send the unit on according to the local company
directives.
If the voltage on pin 2 (0.9 V) or 4 (1.4 V) is incorrect, send the unit on according to the local
company directives.
If the voltages on pin 10,5,2 and 4 are correct, replace L750, C750 and R750.
If the fault still remains, replace N750.
If the fault remains, send the unit on according to the local company directives.
