General Rf Troubleshooting - Nokia 2760 Service Manual

RM-258; RM-259
RF Troubleshooting Instructions

General RF troubleshooting

General RF troubleshooting
Most RF semiconductors are static discharge sensitive
Two types of measurements are used in the following. It will be specified if the measurement type is "RF" or
"LF".
• RF measurements are done with a Spectrum Analyzer and a high-frequency 500 ohm passive probe, for
example HP54006A. (Note that when measuring with the 500ohm probe the signal will be around 20dB
attenuated. The values in the following will have these 20dB subtracted and represent the real value seen
on the spectrum analyzer). Note that the testing have some losses which must be taken into consideration
when calibrating the test system.
• LF (Low frequency) and DC measurements should be done with a 10:1 probe and an oscilloscope. The probe
used in the following is 10Mohm/8pF passive probe. If using another probe then bear in mind that the
voltages displayed may be slightly different. Always make sure the measurement set-up is calibrated when
measuring RF parameters on the antenna pad. Remember to include the loss in the module repair jig when
realigning the phone.
So ESD protection must be applied during repair (ground straps and ESD soldering irons). Mjoelner and Bifrost
are moisture sensitive so parts must be pre-baked prior to soldering. Apart from key-components described
in this document there are a lot of discrete components (resistors, inductors and capacitors) for which
troubleshooting is done by checking if soldering of the component is done properly and checking if the
component is missing from PWB. Capacitors can be checked for short-circuiting and resistors for value by
means of an ohmmeter, but be aware in-circuit measurements should be evaluated carefully. In the following
both the name EGSM and GSM850 will be used for the lower band and both PCN and GSM1900 will be used
for the upper band.
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