User Guide

RH-37
6(b) - RF Troubleshooting Instructions Nokia Customer Care
Page 36 Nokia Corporation Issue 1 07/04
Even if the PLL is not working properly (Vc outside the valid range), a frequency at the
output of the VCO can be detected between 3GHz and 4.4 GHz (if the VCO itself is ok and
the supply voltage VR7 = 2.78V is applied).
If the frequency or the tuning voltage have other values than given above, see the fault
finding chart for PLL syntesizer below.
Fault finding chart for PLL synthesizer
Figure 4: PLL Fault Finding Tree
Yes
Check Baseband part for errors
Phoenix:
Phone is responding to Phoenix commands. For example,
Ctrl-R reads the right phone information.
No
Synthesizer
Fault Finding Tree
part 1
Baseband part is not working,
possible reason: 26MHz missing.
Oscilloscope:
Check VCTCXO supply
(VR3=2.78V, this can be checked after
power on for a time of about
32sec
.
A
fter that time the voltage is going
down.)
Check supply filter components :
C2235, R7516, C7526.
Check UEM and base band part.
No
Oscilloscope
VCTCXO output at G7501
26MHz,app.0.8Vpp
VCTCXO G7501 defective or
short circuit to GND.
No
Yes
Oscilloscope
REFCLK output of N7500:
Signal VCTCXO=RFCLK_I
at C2902, R2902.
26MHz,app.0.8Vpp
No
Yes
Check supply filter components:
R7519, C7522, VDIG at N7500
Check C2902, R2902 and N7500.
Check UEM and Software.
Yes