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Nokia Customer Care
RF Troubleshooting
Introduction to RF troubleshooting
Measurements should be done using Spectrum analyzer with high-frequency high-
impedance passive probe (LO-/reference frequencies and RF power levels) and Oscillo-
scope with a 10:1 probe (DC-voltages and low frequency signals)
The RF-section is built around one RF-ASIC (Helgo N500). For easier troubleshooting, this
RF troubleshooting document is divided in to sections.
Before changing Helgo, please check following things: Supply voltages are OK and serial
communication is coming from baseband to Helgo.
Please note that the grounding of the PA module is directly below PA-module so it is dif-
ficult to check or change. Most RF semiconductors are static discharge sensitive! So
ESD protection must be taken care of during repair (ground straps and ESD soldering
irons). Helgo and PA are moisture sensitive so parts must be pre-baked prior to soldering.
Apart from key components described in this document here are a lot of discrete compo-
nents (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 PWB). Capacitor can be checked for shortening and resistors for value by means of
an ohmmeter, but be aware in-circuit measurements should be evaluated carefully.
Please be aware that all measured voltages or RF levels in this document are rough fig-
ures. Especially RF levels varies due to different measuring equipment or different
grounding of the used probe. When using RF probe usually a good way is to use metallic
tweezers to connect probe ground to PWB ground as close to measurement point as pos-
sible.
Copyright © 2005 Nokia Corporation. All rights reserved.
Issue 2 05/05
Company confidential
NPL-4/5/
Troubleshooting Instructions
Page 7
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Table of Contents
Troubleshooting
