Rf Troubleshooting; Introduction To Rf Troubleshooting - Nokia RH-30 Series Troubleshooting Instructions

RF Troubleshooting

Introduction to RF troubleshooting

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Measurements should be done using Spectrum analyzer with high-frequency high-impedance
passive probe (LO-/reference frequencies and RF power levels) and Oscilloscope with a 10:1
probe (DC-voltages and low frequency signals).
The RF-section is build around one RF-ASIC (HELGO N500). For easier troubleshooting, this
RF troubleshooting document is divided into sections.
Before changing HELGO, please check the following things: supply voltages are OK and serial
communication coming from baseband to HELGO.
Please note that the grounding of the PA module is directly below PA-module so it is difficult to
check or change. Most RF semiconductors are static discharge sensitive! So ESD protec-
tion 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 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 PWB). Capac-
itor 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 figures.
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 possible.
Note! When you are checking RF performance via AMS coupler please remember to
ensure that the antenna is properly assembled and the antenna pogo-pins exist and
are not jammed. If there is poor contact in antenna, the measurement results via cou-
pler can be incorrect or the call can not be established.