Nokia 5140 Manuales De Servicio

NPL-4/5

Company confidential

Troubleshooting Instructions

Nokia Customer Care

Page 50

Issue 1 05/04

Fault finding chart for PLL synthesizer

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’.

Setup with Phoenix:
Band: GSM 1800
Mode: RX Continuous

Channel: 700

Spectrum analyzer

VCO out (G502)

VCO

= 3685.6 MHz

tune

=2.1..2.6V

PLL Block is functional

Yes

Oscilloscope

VCTCXO Supply

(

VR3=2.78V)

Oscilloscope
VCTCXO output at G501

26MHz,app.0.8Vpp

PLL Synthesizer
Fault Finding Tree

Check supply filter components:

C295, C574.
Check BB and SW.

G501 defective or short
circuit to GND.

Oscilloscope
VCO supply

(VR7 = 2.78V, VR5=2.78V)
VR1=4.7V

Spectrum analyzer
VCO out (G502)

Some signal 3-4.4 GHz

Change VCO

Check loop filter components:

C503, C504, C505, R501, R502

Wrong writing on RFBus (see BB part)

If ok change RF ASIC N500

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.

Check supply filter components:

R500, C501, C560, C551, C552, C553

Check UEM and Software.

Yes

Oscilloscope
REFCLK output of N500: Signal
VCTCXO=RFCLK_I at C420, R420.
26MHz,app.0.8Vpp

Yes

Check supply filter components:

R511, C550, VDIG at N500.

Check C420, R420 and N500.

Check UEM and Software.

Yes