Transmitter; General Instructions For Tx Troubleshooting; Path Of The Transmitted Signal - Nokia NSW-5 Series Service Manual

PAMS Technical Documentation

Transmitter

General Instructions for TX Troubleshooting

Always use RF–cable connected from antenna connector to analyzer
through a 10 dB attenuator. This is important to protect analyzer against
excessive rf–power and not to let leake unwanted RF power to the cellu-
lar frequencies.
Start Wintesla–software and select TX mode under testing
(AMPS,DAMPS or TDMA1900). It is useful to select mid channel (383 for
AMPS/DAMPS or 1000 for TDMA1900) and power level 2. Select random
data for digital mode of operation.
One of the basic test is to monitor current when transmitter is on. If cur-
rent consumption does not change when transmitter is set on the fault is
in the PA area.
Nominal current consumptions on power level 2 in mid channel:
AMPS:
TDMA800:
TDMA1900:
Also, if pressing the PA package more tightly to PWB does have an effect
on current consumption the fault is in the PA. In case of a faulty PA, the
replacement should be done only under correct ESD precaution and us-
ing a hot air gun set to 10 m/s and 300 degrees centigrade. The new PA
must be taken from a vacuum package and the heating process should
be done in less than 30 seconds. Note, that the ground slug of the pack-
age must be properly soldered and excessive solder material, if any, has
to be removed.
If any components in the TX chain are replaced, the power level tunings
have to be checked and retuned.

Path of the transmitted signal

AMPS/DAMPS
Cobba TX I/Q DAC – I/Q–modulator – gain step amplifier – linear gain
control amplifier – IF BPF – Upconverter – TX Driver amplifier – BPF–
Power Amplifier – Directional Coupler– Duplexer –Diplexer – Antenna.
TDMA1900D
Cobba TX I/Q DAC – I/Q–modulator – gain step amplifier – linear gain
control amplifier – IF BPF –Upconverter – BPF– TX Driver amplifier –
BPF– Power Amplifier – Directional Coupler– Duplexer – Diplexer – An-
tenna.
Power detection and power control circuits are located under the power
control part of this guide.
Issue 1 10/00
Disassembly and Troubleshooting Instructions
700–900 mA
350–400 mA
400–470 mA
E Nokia Mobile Phones Ltd.
NSW-5
Page 37