Introduction To Rf Troubleshooting - Nokia RH-47 Series Rf Description And Troubleshooting

Nokia Customer Care

Introduction to RF Troubleshooting

This document shall provide instructions, how to check, repair and calibrate RH-47
phones. It is assumed, that the phones are disassembled and tested within a repair jig
MJ-21.
The following types of measurements have to be done for repair of the phone boards:
• RF measurements are made by using a Spectrum Analyzer together with a high-
frequency probe (i.e. hp 85024A Note, that signal levels are not accurate ). Cor-
rect attenuation can be checked using a "good" phone board for example.
• LF (Low frequency) and DC measurements are made with an oscilloscope
together with a 10:1 probe.
• For receiver measurements a signal generator with frequencies up to 2000 MHz
is required. Most of the radio communication testers like CMD55 or CMU200 can
be used as signal generator. The signal generator is connected to the antenna
port using the repair jig MJ-21.
• Output level measurements of the transmitter are made with a power meter or a
calibrated spectrum analyser, which is connected to the antenna port using the
repair jig MJ-21.
Always make sure that the measurement set-up is calibrated when measuring RF param-
eters at the antenna port. Remember to include the correct losses of the module repair
jig and the connecting cable when realigning the phone.
Most RF semiconductors are static discharge sensitive. ESD protection must be taken
into account during repair (ground straps and ESD soldering irons).
Mjoelner RF ASIC is moisture sensitive. Therefore, Mjoelner RF ASIC must be pre-baked
prior to soldering.
Rx calibration done via Phoenix software is temperature sensitive because of calibra-
tion of the 26 MHz reference oscillator (VCXO). According to Mjoelner specification
ambient temperature has to be in a range from 22°C to 36°C.
Apart from key-components described in this document there are a lot of discrete com-
ponents (resistors, inductors and capacitors) for which trouble shooting is done by
checking its proper soldering and complete assembly on the PWB. Capacitors and resis-
tors can be checked by means of an LCR meter, but be aware in-circuit measurements
should be evaluated carefully.
In the following GSM850 will be used for the low band, and PCS or GSM1900 for the
high band.
Note: In this document there are example measurements being depicted with Phoenix Internal Service
Software A2003.42.1.48 pictures.
Issue 1 05/04
Company Confidential
7 - RF Description and Troubleshooting
Copyright © 2004 Nokia Corporation
Company Confidential
RH-47
Page 11