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Customer Care Europe, Middle East & Africa
SCCE Training Group
No or too low TX power GSM 900
Use WinTesla to set phone into following mode: Initialize/ Local mode/Testing/ RF Controls/ active unit TX, Ch.38.
First of all check 26 MHz reference oscillator at C546:
Figure 12-1
Amplitude of spectrum is approximately –10 dBm.
If signal is not ok, check Vtcxo 2.6 VDC at C543/544 and AFC-voltage at C552, which normally is 1.2 VDC but
may vary between 0.3 V and 2.3 VDC. If AFC-voltage is 0 V, especially check R522 and VREF 1.5 VDC at C109.
If DC-voltages are ok but frequency deviation is >100 Hz it is necessary to change G502.
If reference oscillator is working properly, check TXIQ-signals at R541/548:
Figure 12-2
If TXIQ-signals at R541/548 are not measurable or somehow corrupted, check the following signals
for COBBA N100: VBB 2.8 VDC at C119, VCOBBA 2.8 VDC at C116/117, VREF 1.5 VDC at C109 and
13 MHz COBBACLK at J317:
Figure 12-3
If the above mentioned signals for COBBA N100 are ok but TXIQ-signals are not measurable,
probably COBBA is faulty or has broken solderings under it. Remove COBBA, rework oxidized pads if necessary
with flux and solder and replace spare part with µBGA rework machine.
Note that it is necessary to rewrite SIMlock-data, make SW-update and retune RX/TX-values of the phone
after changing COBBA N100!
© NMP 2002
CONFIDENTIAL
NHM—2/5/6
3410
Date 20.11.2002
Checked by:
Customer Care E&A
34 (44)
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Version 4.0 Approved
Approved by:
SCCE Training Group
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