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Table below shows the limits for the VCXO measurements Table.6.1.
Parameter
VCXO Control at
DAC 00 Hex
VCXO Control at
DAC 3FF Hex
Control Range
Calibrated VCXO
6.3
How to find the fault
Open the phone and check for liquid damages.
No further action should be taken for a liquid damaged telephone.
Start the phone in the test program.
Start the transmitter in static mode at channel 699. Make sure the transmitter locks on.
Turn off the modulation by selecting "Mod off".
Go to Misc /DAC Parameter.
Set TCXO to 00 Hex.
Notice that the DAC value does not change until clicking at "Close".
Measure the DC voltage at C511 +0.3 V
Set TCXO to 3FF Hex.
Notice that the DAC value does not change until clicking at "Close".
Measure the DC voltage at C511 +2.9 V
If both voltages are correct, but any of the VCXO measurements are incorrect, the fault usually
is due to B510. Sometimes the fault is due to V510, C512, C513 or C510.
If both voltage are constantly too low, remove C511.
Measure the voltage again.
If the voltage is correct now, the fault was a short circuit in the capacitor.
If the fault remains, it usually is due to N800 or C853.
The voltage at a correct C853 is +1.2 V
If both voltages are equal, but not zero V
If both voltages are correct, but the VCXO calibration is incorrect, the fault usually is due to
B510 or V510. Sometimes is it due to C510, C512 or C513.
VCXO faults can be due to N500, but that is not very common.
4/00021-3/FEA 209 544/18 B
Min.
-67
13
VCXO
40
262
DAC
106
Table.6.1
Tax
Unit
-13
ppm
67
ppm
80
ppm
762
Dec.
2FA
Hex
.
DC
.
DC
DC
, the fault is almost always due to N800.
DC
Trouble Shooting Guide, Advanced
29(121)
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