Rf Troubleshooting - Nokia Mobile Phones NSE-5 Series Service Manual

PAMS
Technical Documentation

Rf Troubleshooting

Measurements should be done using a spectrum analyzer with a
high–frequency 500 ohm passive probe (LO–/reference frequencies and
RF–powerlevels) and oscilloscope with a 10:1 probe (DC–voltages and
low frequency signals).
RF–section is mainly built from two ASICS CRFU3 (N600) and SUMMA
(N700), external filters, MMIC PA–modules (N500, N501) and two
synthesizers. For easier troubleshooting, this is divided into five sections:
GSM Receiver, GSM Transmitter, PCN Receiver, PCN Transmitter and
Synthesizer parts. The tolerance is specified for critical signals/voltages.
Before changing either of the ASICS, please check the following things:
The soldering and connections of pins of the ASICS are OK, supply
voltages are OK and the signals of the synthesizers are coming to ASICS.
This will prevent the unnecessary changing of the ASICS.
Please note that the grounding of the PA–module is directly below the
PA–module so it is difficult to check. The PA–module is static discharge
sensitive! So ESD protection must be used when dealing with
PA–module (ground straps and ESD soldering irons). The PA is also class
3 moisture sensitive so parts must be dry bake.
Check that discrete components i.e resistors,inductors and capacitors are
not missing and are soldered properly.
Issue 1 07/99
Figure 1. PCB Top View
NSE–5
Troubleshooting
Page 21