User Guide

Table Of Contents

NHL-12

Nokia Customer Care 7 - RF Description & Troubleshooting

12 COMPANY CONFIDENTIAL Issue 2 10/2004

3. Introduction to RF troubleshooting

All measurements must be done using a spectrum analyzer with a high-frequency high-imped-

ance passive probe (LO-/reference frequencies and RF power levels) and an oscilloscope with

a 10:1 probe (DC-voltages and low frequency signals).

The RF section is build around one RF ASIC (HELGO N7300). Before changing HELGO,

please check the following things: supply voltages and serial communication coming from

baseband to HELGO are both OK.

Apart from key components described in this document here are a lot of discrete components

(resistors, inductors and capacitors) which troubleshooting is done by checking if soldering of

the component is done properly (for factory repairs checking if it is missing from the PWB). Ca-

pacitor can be checked for shortening and resistors for value by means of an ohmmeter, but

be aware that in-circuit measurements should be evaluated carefully.

Please be aware that all measured voltages or RF levels in this document are rough figures.

Especially RF levels vary due to different measuring equipment or different grounding of the

used probe. When using the RF probe, use metallic tweezers to connect the probe ground to

the PWB ground as close to the measurement point as possible.

Please note that the grounding of the PA module is directly below PA module, therefore 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).

HELGO and PA are moisture sensitive which means that parts must be pre-baked prior to sol-

dering.

For easier troubleshooting, this RF troubleshooting document is divided into sections.