User Guide

Table Of Contents

General RF troubleshooting

Introduction to RF troubleshooting

Most RF semiconductors are static discharge sensitive

ESD protection must be applied during repair (ground straps and ESD soldering irons).

Pre-baking

These parts are moisture sensitive and must be pre-baked prior to soldering:

• RF IC N7505

• TXFEM N7520

• DC/DC Converter N7590

• Tx Saw GSM 850/900 Z7503

• Rx Saw GSM 1800/1900 Z7501

Note: Please review the appropriate process for storage and handling of these components prior

to soldering.

Discrete components

In addition to the key-components, there are a number of discrete components (resistors, inductors and

capacitors) for which troubleshooting is done mainly by

visual inspection

Capacitors: check for short circuits.

Resistors: check value with an ohm meter.

Note: In-circuit measurements should be evaluated carefully

Measuring equipment

All measurements should be done using:

• An oscilloscope for low frequency and DC measurements. Recommended probe: 10:1, 10Mohm//8pF.

• A radio communication tester including RF generator and spectrum analyser, for example Rohde & Schwarz

CMU200. (Alternatively a spectrum analyser and an RF generator can be used. Some tests in this guide are

not possible to perform if this solution is chosen).

Note: All measurements with an RF coupler should be performed in an RF-shielded environment

because nearby base stations can disturb sensitive receiver measurements. If there is no possibility

to use RF shielded environment, testing at frequencies of nearby base stations should be avoided.

Level of repair

The scope of this guideline is to enable repairs at key-component level. Some key-components are not

accessible, i.e. not replaceable. Please refer to the list of Non-replaceable RF components (page 4–6).

RM-429

RF troubleshooting

Issue 1 COMPANY CONFIDENTIAL Page 4 –5