Rf Troubleshooting; Introduction To Troubleshooting - Nokia NHM-1 Series Troubleshooting Instructions
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Also See for NHM-1 Series:
- Technical documentation manual (8 pages) ,
- Software instructions (86 pages) ,
- Service manual (25 pages)
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CCS Technical Documentation
RF Troubleshooting
Introduction to 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 GSM RF-section is build around one RF-ASIC (HELGO N600). WCDMA RF is based on
RX ASIC REX and TX ASIC TEX. For easier troubleshooting, this RF troubleshooting docu-
ment is divided in to sections.
Before changing RF system-ASIC, please check following things: Supply voltages are OK
and serial communication coming from baseband to HELGO/REX/TEX.
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 duriong repair (ground straps and ESD soldering
irons). RF ASICs and PAs are moisture sensitive so parts must be pre-baked prior to sol-
dering.
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.
Please be aware also that when testing transmitters, the TX power should be loaded
always with 50 ohm dummy load – never antenna!!. Especially in WCDMA, where extra
TX power in cell harms a lot the capacity or range of the cells.
Connect test jig to computer with DAU9S cable or to FPS-8 Flash Prommer with XCS-4
modular cable.
Make sure that you have PKD-1 dongle connected to computers parallel port.
Connect DC power supply to module test jig with FLC-2 cable.
Attention: When repairing or tuning transmitter use external DC supply with at
least 3A current capability. Set the DC supply voltage to 3.9V and set the jumper con-
nector on test jig to "bypass" position.
Issue 1 11/03
Nokia Corporation.
NHM-1
Troubleshooting instructions
Page 5
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Troubleshooting
