Tdma1900; Fig 25 If Signal Level; Fig 40 Tdma1900 - Nokia RH-13 Series Troubleshooting Manual

RH-13
Troubleshooting
3 Set phone receiver to continuous mode with full gain using Phoenix (see figure
23, RF controls, in step 3).
4 Connect spectrum analyzer probe to the output of GSM IF filter (at the one end
of R804) and record the level.
5 Connect spectrum analyzer probe to the input of GSM IF filter (at the one end of
R803) and record the level.
• If the IF signal levels are according to the picture below and local oscillators are
OK (see step 2 Local oscillator checking) but RX I/Q signal is not correct (see step
3 to check RX I/Q signal) the problem is probably due to malfunction of either
2nd mixer or AGC blocks inside Safari.
• If the IF signal level is correct at the filter input but not at the output side the fil-
ter shall be replaced with new one.
• If the IF signal level is not correct at the filter input side and the local oscillators
are functioning properly, inductors L814 and L815 should be checked, as well. If
they are OK and there is a signal at the input of the 1st mixer, the problem is
probably due to a faulty 1st mixer inside Safari.
LNA gain step function can be checked by measuring signal level at L806 and turning ON
and OFF the LNA using Phoenix. The gain should change by 20...30 dB.

TDMA1900

Only path from external RF connector to IF needs to be checked if AMPS/TDMA800/
GSM850 RX chain is OK. After down conversion (from RF to 134.04 MHz IF) both lower
and upper band use same signal path.
Page 42
Figure 25: IF signal level
ãNokia Corporation
CCS Technical Documentation
Issue 1 11/02