Nokia 7270 Service Manual
Issue 2 03/2005
COMPANY CONFIDENTIAL
42
Copyright © 2005 Nokia. All Rights Reserved.
RM-8/RM-47/RM-48
Nokia Customer Care
RF Troubleshooting
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).
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 N7500). For easier troubleshooting, this
RF troubleshooting document is divided into sections.
RF troubleshooting document is divided into sections.
Before changing HELGO, please check following things: Supply voltages are OK and serial
communication is coming from baseband to HELGO.
communication is 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 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.This does not apply to
parts taken directly out of a moisture barrier bag.
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.This does not apply to
parts taken directly out of a moisture barrier bag.
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 soldering of the
component is done properly (for factory repairs checking if it is missing from PWB). Capacitors
can be checked for shortening and resistors for value by means of an ohmmeter, but be aware
in-circuit measurements should be evaluated carefully.
(resistors, inductors and capacitors) which troubleshooting is done by checking soldering of the
component is done properly (for factory repairs checking if it is missing from PWB). Capacitors
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 vary due to different measuring equipment or different grounding of the
used probe. When using RF probe a good way is to use metallic tweezers to connect probe
ground to PWB ground as close to measurement point as possible.
Especially RF levels vary due to different measuring equipment or different grounding of the
used probe. When using RF probe a good way is to use metallic tweezers to connect probe
ground to PWB ground as close to measurement point as possible.