Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
33(78)
Table 9.1. shows the limits for the VCXO measurements.
Parameter Min Max Unit
VCXO DAC 262 762 Dec
106 2FA Hex
Table 9.1
9.2 How to find the fault
Open the phone and check for liquid damage.
No further action should be taken for a liquid damaged unit, send it on according to the
local company directives.
Start the board in EFRA with the test program.
Go to Misc /DAC Parameter.
SetVCXOto00Hex.Notice that the DAC value does not change until clicking at ”Close”.
Measure the DC voltage at C320, 0.3 V
DC
.
Set VCXO to 3FF Hex. Notice that the DAC value does not change until clicking at “Close”.
Measure the DC voltage at C320, 2.5 V
DC
.
If both voltages are correct, but any of the VCXO measurements are incorrect, the fault
usually is due to B320.
Sometimes the fault is due to V321, V322, C321 – C324, R322 or R321.
If both voltages are constantly too low, remove C320. Measure the voltages again.
If the voltages are correct now, the fault was a short circuit in the capacitor.
If the fault remains, it usually is due to N500 or C511.
The voltage at a correct C511 is 1.2 ± 0.10 V
DC.
If both voltages are equal, but not 0.0 V
DC
, the fault is almost always due to N500.
If both voltages are correct, but the VCXO calibration is incorrect, the fault usually is due to
B320, V321 or V322.
Sometimes is it due to C321 – C324.
VCXO faults can be due to N300, but that is not very common.
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