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Figure 10:RX-Control Signal
Call breaks / No service
G701 13MHz Oscillator out of range or high spurious emission
Set the handset to call mode, check if some phase and frequency errors appear special in GSM 1800 band
The deviations will be higher the higher the traffic channel is!
Change the G701 13MHz Oscillator
COBBA N200 broken solder balls
Check VBB 2,8V DC on C117 near to CCONT
Check VCOBBA 2,8V DC C148 near to COBBA
Check COBBACKL 13MHz 3,2Vpp on J 201 (see the diagram in chapter "COBBA contact service" )
Check the module in call modus with a simulator.
Knock very careful with something no metalled around the COBBA
Check if some errors appear on the tester (phase /frequency / RX-Quality/TX-Power level)
Check the COBBA IC with a microscope, the first broken balls are normal on the corners from circuit.
Change the circuit with a μBGA solder machine
version 1.0 / 05.11.1999
CONFIDENTIAL
Service & Analysis Center Europe
Training Team
Page 33 of 37
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