Introduction To Rh-53/54 Rf Troubleshooting - Nokia 2650 Service Manual

RH-53/54

Introduction to RH-53/54 RF Troubleshooting

Three types of measurements are used in the following. It will be specified if the measurement
type is "RF" "RF test" or "LF".
• RF measurements should be done with a GSM tester and a suitable connector to
the general RF input/output. That connection is for tuning and testing the whole RF
in the phone.
• RF test measurements should be done with a Spectrum Analyzer and a high-fre-
quency 500ohm passive probe, for example HP54006A. Use some sort of DC block-
ing device, to avoid loading the circuit or the SPA with DC. (Note that when
measuring with the 500ohm probe, the signal will be around 20 dB attenuated. The
values in the following will have these 20 dB subtracted and represent the real value
seen on the spectrum analyzer).
• LF (Low frequency) and DC measurements should be done with a 10:1 probe and
an oscilloscope. The probe used in the following is 10MΩ/8pF passive probe. If us-
ing another probe then bear in mind that the voltages displayed may be slightly dif-
ferent.
Always make sure the measurement set-up is calibrated when measuring RF parameters on
the antenna connector. Remember to include the loss in the module repair jig and the coaxial
cable when realigning the phone.
Most RF semiconductors are static discharge sensitive. So ESD protection must be taken
during repair (ground straps and ESD soldering irons). Mjoelner is 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 or checking if the component is missing from PCB. Capac-
itors can be checked for short-circuit 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 "low band" will be used to describe both GSM850 - EGSM and
GSM900, while "high band" will be used for both PCN and GSM1800.
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