Ericsson R320s Working Instruction page 32

Trouble Shooting Guide, Standard
5.4 Background illumination glows faintly or does not
work at all
Open the phone and check for liquid damage.
Clean X750 if needed (fig. 5.1).
Replace the illumination panel.
Note! The illumination is only lit for about 25 seconds, press any key to light it again.
Fig. 5.1
Power up the board and start it by pressing the ON/Off key.
Measure the voltage at pin 6 and 8 of N750 (23 V, fig. 5.1).
If the voltage is incorrect, measure the voltage at pin 10 (3.70 V), pin 5 (2.70 V), pin 2 (0.9
V) and at pin 4 (1.3 V) of N750.
If the voltage at pin 10 is incorrect, measure the resistances of L750 (3 ohms), C751 (>1
Mohms) and the resistance at L750, at the side close to N750, to VBATT (0 ohms).
If any of the L750 or C751 resistances are incorrect, replace the corresponding component.
If the resistance from L750 to VBATT is incorrect there is a foil damage, send the unit on
according to the local company directives
If the voltage at pin 5 is incorrect, send the unit on according to the local company directives
If the voltage at pin 2 or 4 is incorrect, send the unit on according to the local company
directives
If the voltages are correct, replace L750, C750 and R750.
If the fault still remains, replace N750.
If the fault remains after replacing N570, send the unit on according to the local company
directives.
4/00021-2/FEA 209 544/21 B 16(26)