User Guide

NHL-12
Nokia Customer Care 7 - RF Description & Troubleshooting
42 COMPANY CONFIDENTIAL Issue 2 10/2004
Copyright © 2004 Nokia. All Rights Reserved.
Troubleshooting chart for PLL synthesizer
Figure 18:Frequency synthesizer troubleshooting
Synthesizer
troubleshooting
Synthesizer
OK
Yes
*(When 2.5kOhm passive probe is used,
correct the measurement by +34 dB
Replace
VCO
Replace
faulty
component(s)
Yes
Yes
No
Set with RF controls:
Active Unti = Rx
Operation mode = Continuous
Check with RF probe:
- 4G VCO out signal
- 3526.4 MHz (GSM850)
- 3685.6 MHz (GSM1800)
- 3920 MHz (GSM1900)
Level >-10dBm (*
OK ?
VCO out signal level<-10dBm
Check balun
output levels and
solder joints
OK ?
Check output signal on
1 GHz span
Signal found on
incorrect frequency ?
Check with oscilloscope:
-4G VCO Vcc = 2.8V
OK ?
Baseband
troubleshooting
Check with oscilloscope:
Check with oscilloscope:
VCO control voltage
VCO control voltage
from VCO pin
from VCO pin
0V ?
>4.0 V ?
Replace
VCO
Check balun
output levels and
solder joints
OK ?
Check VCO control
loop components
OK ?
Replace
faulty
component(s)
No
No
Yes
Yes
Yes
No
Yes
No
No
Yes
No
No
Yes