Fault Finding Chart For Pll Synthesizer - Nokia RM-94 Rf Troubleshooting Instructions

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Fault finding chart for PLL synthesizer

Phoenix:
Phone is responding to Phoenix commands. For example,
Ctrl-R reads the right phone information.
Yes
Baseband part is not working,
possible reason: 26MHz missing.
Oscilloscope
VCTCXO output at G7501
26MHz,app.0.8Vpp
Oscilloscope:
Check VCTCXO supply
(VR3=2.78V, this can be checked after
power on for a time of about 32sec.
After that time the voltage is going
down.)
34
Figure 4:PLL Fault Finding Tree
No
Yes
No
Oscilloscope
REFCLK output of N7500:
Signal VCTCXO=RFCLK_I
at C2902, R2902.
26MHz,app.0.8Vpp
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6(b) - RF Troubleshooting
Yes
Check Baseband part for errors
Check supply filter components:
R7519, C7522, VDIG at N7500
Check C2902, R2902 and N7500.
No
Check UEM and Software.
VCTCXO G7501 defective or
Yes
short circuit to GND.
Check supply filter components :
No
C2235, R7516, C7526.
Check UEM and base band part.
RM-94
Synthesizer
Fault Finding Tree
part 1
Issue 1 04/2005