Trouble Shooting Guide, Standard
4/00021-2/FEA 209 544/31 B 5(23)
2.1 Find out if the fault is RX- or TX-related
Connect the phone to a GSM test instrument and try to get SERV at an input signal strength
of -68.5dBm.
If the phone does not get SERV at one or both bands, go to section 2.2.
If the phone gets SERV, go to section 2.3.
2.2 The phone does not get SERV
Open the phone and check for liquid damage. Make sure that the antenna connector in the
frame is not mechanically damaged, dirty or oxidised. Clean or replace it if it is needed. Also
check that the antenna connector surface on the board is clean and that it is not oxidised.
Check the soldering of N234, N200, Z200, Z201 and N201.
Measure the resistance of R220, R221, R222 and R223 (all 2.7 kohms).
Replace it if it is incorrect.
Check that C312 is correctly soldered.
If the fault is not found so far, the problem is probably within the LO part or the losses in the
signal path might be too large. It is also possible that the feed voltages are incorrect. Power up
the board and start it by pressing the On/Off key.
Measure the VRAD voltage on C501, on the pin close to N700 (3.8V).
If the voltage is incorrect, send the unit on according to the local company directives.
Measure the V380B voltage on C500, on the pin close to R427 (3.8V). If the voltage is
incorrect, send the unit on according to the local company directives.
Measure the VVCO voltage on pin 5 of N502 (3.8V).
If the voltage is correct, go to section 2.2.1.
If the voltage is incorrect, measure the voltage on L500 (VBATT).
If the voltage on L500 is correct, measure the voltage on V500, on the pin close to C401 (4.7
V).
If the voltage on V500 is correct, measure the voltage on pin 1 of N502 (4.7 V).
If the voltage on pin 1 of N502 is correct, measure the voltage on pin 3 of N502 (3.8V).
If the voltage on pin 3 of N502 (3.8V) is correct, replace N502.
If the voltage on pin 3 of N502 (3.8V) is incorrect send the unit on according to the local
company directives.
If the voltage on pin 1 of N502 is incorrect send the unit on according to the local company
directives.
If the voltage at V500 is 3.8V, replace V500, otherwise send the unit on according to the local
company directives.
If the voltage at L500 is incorrect, measure the resistance of L500 (0 ohms).
If the resistance is correct, send the unit on according to the local company directives.
If the resistance is too high, replace L500.
2.2.1 Check the feed voltages
VRAD voltage for N234:
