CCS Technical Documentation
Troubleshooting Instructions
NSB-9
Issue 1 04/03
Nokia Corporation
Page 5
TROUBLESHOOTING IN CASE OF RF TUNING FAIL
Channel Select Filter Calibration
Calibration is done using internal calibration circuit (UEM sends and receives a test sig-
nal to/from Hagar). VCO (G650), RX-bandfilters (Z501, Z551) and TX-filter/balun (Z700,
T700) don't have any effect to the Channel Select Filter Calibration. Instead, baseband
shall be functional (=VCTCXO G660 is running). Any failure in Hagar, its supply voltages
or RX/TX IQ-lines may cause this calibration to be failed.
If baseband works and there are not any visible cause around Hagar (missing or broken
components etc.), Hagar shall be replaced at first place.
RX Calibration
The most probably reason for this is lack of gain in receiver chain. Check rx chain accord-
ing to RX850/1900 fault finding charts. In GSM850 RX, components Z520, V500 and
Z501 should be checked. In GSM1900 RX, components Z520, V550 and Z551 should be
checked.
If signal seems to pass rx chains with adequate gain, VCO function shall be checked. It is
also possible that signal passes rx chain to Hagar and VCO is functional but signal
doesn't appear in RX IQ-lines. In this case, Hagar shall be replaced.
RX AM Suppression Calibration
RX AM Suppression Calibration limits (LOPI, LOMI, LOPQ and LOMQ) are so wide that the
calibration results can't exceed the limits. Instead, RSSI value measured after tuning may
be too high. Also in this case, replacing Hagar may improve the result.
RX Band Filter Response Compensation
If RX Calibration results are ok but this compensation fails, the most probably reason for
this is lack of gain (or too big gain) in receiver chain in some frequency. Check rx chain
according to RX850/1900 fault finding charts. Retest rx chain also in low and high chan-
nels. In GSM850 RX, components Z520 and Z501 should be checked. In GSM1900 RX,
components Z520 and Z551 should be checked.
TX Power Level Tuning
The most likely reason for this is lack of gain in transmitter chain. Check tx chain accord-
ing to TX850/1900 fault finding charts. In GSM850 TX, components Z500, L750, N700
and Z700 should be checked. In GSM1900 TX, components Z500, L750, N700 and T700
should be checked.
If signal seems to pass tx chains with adequate gain, VCO function shall be checked. It is
also possible that signal doesn't appear in TX IQ-lines. In this case, baseband shall be
checked.
TX IQ Tuning
TX IQ tuning fails, if IQ-spikes in the spectrum can't be tuned low enough. If replacing
Hagar doesn't help with this issue, VCO component (G650) and components around it
