Nokia NHM-7 series, Service Manual, Page: 144 / 212

NHM–7
Troubleshooting Instructions
PAMS Technical Documentation
Page 24 Issue 1 10/2001
Nokia Corporation
RF Troubleshooting
Introduction
Measurements should be done using spectrum analyzer with high–fre-
quency 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 (HAGAR N600). Before
changing HAGAR, please check following things: Supply voltages are OK
and serial communication coming from baseband to HAGAR.
Please note: Grounding of the PA module is directly below PA module
making it 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). HAGAR and PA
are moisture sensitive and must be pre–baked prior to soldering.
Troubleshooting discrete components (resistors, inductors and capaci-
tors) is done by checking component soldering. Capacitors can be
checked for shortening and resistor values using an ohmmeter, but re-
member in–circuit measurements are evaluated with caution.
Remember that all measured voltages or RF levels in this document are
rough figures. Especially RF levels vary due to different measuring equip-
ment or different probe grounding used . When using RF probe it is good
to use metallic tweezers to connect probe ground to PWB ground as
close to measurement point as possible.