
CCS Technical Documentation
Troubleshooting Instructions RF
NPM-10
Issue 1 03/2003
Nokia Corporation Confidential
Page 31
Troubleshooting Chart for PLL Synthesizer
Figure 23: PLL troubleshooting chart
If the phone stops working a short time after the power is turned ON, a possible reason
for this might be that the 26 MHz system clock signal is not getting to the UPP clock-
input in Baseband. In this case, check the following:
Turn on the phone and check
VCXO Power supply (C620) = 2.7V
VCXO output (R420 – end
not
connected to C420) is 26MHz and approx.
700mVpp
If this is not the case check the reference crystal (B600), Mjoelner (N600), R420, R426,
C420, and C426.
From Phoenix chose:
File > Choose Product > NPM-10
Mainenance > Testing > RF Controls >
GSM1900 > RX > continuous > Ch 661
Spectrum Analyzer
VCO frequency
(R656)
3920.0 MHz
No
Yes
PLL block functional
Oscilloscope
VCXO Power
Supply (C620)
2,7 V
Oscilloscope
VCXO output
(R420) 26 MHz,
approx. 700mVpp
Oscilloscope
VCO Power Supply
(R656)
2,7 V
Check UEM, Software??
Phone not in function
Check UEM, Software??
Phone not in function
Spectrum Analyzer
VCO output (R656)
Some signal
between 3 and 4
GHz
VCO (N601) is not
functional
Yes
No
No
Yes
Yes
Yes
No
Oscilloscope
PLL Power Supply
(C665 & C634)
ALL 2,7 V
Check UEM, Software??
Phone not in function
No
Yes
Yes
VCXO is not functional
Check Crystal (B600)
No
Oscilloscope:
Measure
Control Voltage C641
between 0.5 and 4.0 V
Check
Loopfilter R618,R619,
C639-C641
Check
Mjoelner N600,
UPP D400,
RFBusClk J608,
RFBusDA J610,
RFBusX j609
& Reset_Mjoel
No
Yes