Advertisement
Customer Care Europe, Middle East & Africa
SCCE Training Group
No RX-calibration GSM 900 possible
Use WinTesla to set phone into local mode and activate under /Testing/RF Controls/ RX Ch.38, burst mode.
Set RF-generator to RF-level output of –65 dBm.
The first of all, check signal of 26 MHz reference oscillator at C546 (see figure 12-1 on page 34), as in case of TX-faults:
Amplitude of spectrum is around –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, check especially R522 whether turn off or defect.
If DC-voltages are ok but frequency deviation is >100 Hz, it is necessary to change G502.
If reference oscillator works well, check 942.6 MHz RX-signal at C545:
Figure 12-17
Amplitude of RX-signal at C545 is approximately –67 dBm.
If signal is not measurable or amplitude is too low, check solderings of C593 and C556. Ensure that attenuation
of filter Z501 is not higher than 3.5 dBm. In case of temporary receiver faults, check with microscope especially if
ceramic bottom plate of diplexer Z502 is broken!
In case that 942.6 MHz RX-signal at C545 is ok, check same signal at C534:
Figure 12-18
Amplitude is around –52 dBm. Check solderings of C537. Also ensure that LNA V501 works:
Check with an oscilloscope voltages at base (figure 12.19, 1.1 Vpp) and collector (figure 12.20, 2.6 Vpp) of V501,
change V501 or N500 if necessary.
© NMP 2002
Figure 12.19
CONFIDENTIAL
NHM—2/5/6
3410
Date 20.11.2002
Figure 12.20
Checked by:
Customer Care E&A
40 (44)
Repairhints
Version 4.0 Approved
Approved by:
SCCE Training Group
Advertisement
