User Guide

Introduction to RF troubleshooting
All measurements should be done using:
• spectrum analyser with a high-frequency high-impedance passive probe (LO-/reference frequencies and
RF power levels)
• oscilloscope with a 10:1 probe (DC-voltages and low frequency signals)
Caution: Also all measurements with an RF coupler should be performed in RF shielded environment
because nearby base stations can disturb sensitive receiver measurements. If there is no possibility
to use RF shielded environment, it should be checked that there are no transmissions on the same
frequencies as used in the tests.
The RF section of the phone is build around one RF ASIC: ASIC N7505.
Note: Before changing N7505, please check the following things: supply voltages and serial
communication coming from baseband toN7505 are OK. Please note that the grounding of the Frond
End Module (FEM) is directly below FEM so it is difficult to check or change.
Most RF semiconductors are static discharge sensitive! ESD protection must be taken care of during repair
(ground straps and ESD soldering irons). N7505 and FEM are moisture sensitive, so parts must be pre-baked
prior to soldering.
In addition to key components, there are lot of discrete components (resistors, inductors and capacitors)
which troubleshooting is done mainly by checking if the soldering of the component is done properly.
Capacitor can be checked for shorts and resistors for value by means of an ohmmeter, but be aware in-circuit
measurements should be evaluated carefully as other components connected to the same node can change
the seen resistance.
Keep in mind that all measured voltages or RF levels depicted in the service manual are rough figures.
Especially RF levels vary because of different measuring equipment or different grounding of the probe used.
When using an RF probe, use a pair of metallic tweezers to connect the probe ground to the PWB ground as
close to the measurement point as possible. If measurements are performed in a product specific module
jig, then “GND” pads should be used for the probe ground.
Receiver troubleshooting
Introduction to RX troubleshooting
Rx can be tested by making a phone call or in the local mode. For the local mode testing, use Phoenix service
software.
The main Rx troubleshooting measurement is RSSI measurement. This test measures the signal strength of
the received signal. I and Q branches can be measured separately.
In GSM, the input signal can be either a real GSM signal or a CW signal that is 67.771kHz up from the carrier
frequency.
For service tool usage instructions, refer to section Service Tools and Service Concepts.
General instructions for RX troubleshooting
Steps
1. Connect a test jig to a computer with a DKU-2 cable or to a FPS-10 flash prommer with a modular cable
(XCS-4).
Make sure that you have a PKD-1 dongle connected to the computer's parallel port.
2. Connect a DC power supply to a module test jig (MJ-69).
RM-170; RM-171
RF Troubleshooting and Manual Tuning Guide Nokia Customer Care
Issue 1 COMPANY CONFIDENTIAL Page 7 –5
Copyright © 2006 Nokia. All rights reserved.