Fault Finding Chart For Pll Synthesizer - Nokia RH-37 Series Rf Troubleshooting Instructions

RH-37
6(b) - RF Troubleshooting Instructions
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

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.)
Page 36
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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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.
Synthesizer
Fault Finding Tree
part 1
Issue 1 07/04