Fault Finding Chart For Pll Synthesizer - Nokia NPL-4 Series Troubleshooting Instructions

NPL-4/5/RM-104
Troubleshooting Instructions

Fault finding chart for PLL synthesizer

Setup with Phoenix:
Band: GSM 1800
Mode: RX Continuous
Channel: 700
Spectrum analyzer
VCO out (G502)
f = 3685.6 MHz
VCO
U =2.1..2.6V
tune
Yes
Oscilloscope
REFCLK output of N500: Signal
VCTCXO=RFCLK_I at C420, R420.
26MHz,app.0.8Vpp
PLL Block is functional
Check loop filter components:
C503, C504, C505, R501, R502
Wrong writing on RFBus (see BB part)
If ok change RF ASIC N500
It is important to note that the power supply VR3 of the VCTCXO is only switched off in
the so-called 'Deep Sleep Mode' and the power supply VR7 of the VCO (G502) is switched
off in so-called 'Sleep Mode'.
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BB not working because 26MHz missing.
For a failure free working of BB the 26MHz clock is necessary!
If the 26MHz clock is not working please check first the
necessary voltage VR3. This can be checked after power on for
a time of about 32sec. After that time the voltage is going down.
Oscilloscope
VCTCXO Supply
No
No
(
VR3=2.78V)
Yes
Oscilloscope
VCTCXO output at G501
26MHz,app.0.8Vpp
Yes
Yes
Oscilloscope
VCO supply
(VR7 = 2.78V, VR5=2.78V)
VR1=4.7V
Yes
Spectrum analyzer
VCO out (G502)
Some signal 3-4.4 GHz
Yes
PLL Synthesizer
Fault Finding Tree
Check supply filter components:
C295, C574.
Check BB and SW.
G501 defective or short
No
circuit to GND.
Check supply filter components:
R511, C550, VDIG at N500.
No
Check C420, R420 and N500.
Check UEM and Software.
Check supply filter components:
No
R500, C501, C560, C551, C552, C553
Check UEM and Software.
Change VCO
No
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Issue 2 05/05