Transmitter Fault - General; Path Of The Transmitted Signal - Nokia NSC/W–1/3 Series Disassembly & Troubleshooting Instructions

PAMS
Technical Documentation
Transmitter Fault – General
Always use a RF–cable connected from an external RF connector to the
analyzer via a 10dB attenuator. This is important to protect the analyzer
against excessive RF power and to not let unwanted RF power leak in the
cellular frequencies.
Start the WINTESLA software and select the TX mode for testing (AMPS,
DAMPS, or TDMA 1900). Select mid channel (383 for AMPS, DAMPS or
1000 for TDMA 1900) Select random data for digital mode of operation.
One of the basic test is to monitor current when transmitter is on. If the cur-
rent consumption does not change when transmitter is turned on, the fault
is in the PA. Also if pressing the PA chip more tightly to PCB does have an
effect on current consumption, the fault is in PA.
In case of a faulty PA the IC can be changed only under correct (ESD)
grounding and using only a hot air blower set to 10m/s and 300 degree centi-
grade. The new chip must be taken from its vacuum package and the heating
process must be done in less than 30 second. Note that the bottom plate of
the chip must be properly soldered and excessive solder material, if any, has
to be remove.
If any components in the TX chain are replaced the power level tunings have
to be checked and retuned.

Path of the transmitted signal

Block level listing AMPS, DAMPS
COBBA TX I/Q DA–converters
I/Q modulator and Digital gain step amplifier
IF–BPF
Upconverter
TX Driver
BPF
PA
Coupler
Duplex filter
Antenna matching circuit
EXT RF connector
Antenna
Power detection and power control circuit are included in the power control
part of this guide.
Start the WINTESLA software and set the phone in Analog mode. Set Chan-
nel 383 and Power level 2. Apply the RF cable to Ext RF onnector and con-
nect the cable to the spectrum analyzer input, measure the RF level. Notice
the insertion loss of the cable and the attenuators. Use external attenuator
to avoid overloading the spectrum analyzer.
Original 11/99
Disassembly & Troubleshooting Instructions
Block level listing TDMA 1900
COBBA TX I/Q DA–converters
I/Q modulator and Digital gain step amplifier
IF–BPF
Upconverter
BPF
TX Driver
BPF
PA
Coupler
Duplex filter
Antenna matching circuit
EXT RF Connector
Antenna
NSC/W–1/3
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