RH-109
RF troubleshooting
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:
• PA U1201
• PA U1204
• GPS LNA U1001
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 analyzer, for example Rohde & Schwarz
CMU200. (Alternatively a spectrum analyzer and an RF generator can be used. Some tests in this guide are not
possible to perform if this solution is chosen).
Note:
A mobile phone CDMA2000 transmitter should never be tested with full TX power (only it
possible to perform the measurements in a good RF-shielded room). Even low power CDMA2000
transmitters may disturb nearby CDMA networks and cause problems to 3G cellular phone
communication in a wide area.
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.
Note:
If the RF shielding can is removed (for measurement or repair), it must always be replaced with
a new one.
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