Wcdma Tx Synthesizer Troubleshooting Diagram - Nokia NHM-1 Series Troubleshooting Instructions

CCS Technical Documentation

WCDMA TX Synthesizer troubleshooting diagram

Activate TX synthesizer by setting
Ch. 9750 and pressing "Send"
Iin Tx Control ( WCDMA) window.
Measure the DC-voltage in G900
control voltage input, or in C928.
Is it between 2.0 ... 2.5 V ??
NO
Check VCO output at 1 GHz span,
when center in 3900MHz
Is the signal on incorrect frequency
NO SIGNAL
If there is no output signal,
Check the supply voltage for VCO,
measure from C907, R916.
Do you see Ext Reg1 regulator
output at ca. 2.8 V ??
YES
Check balun T902.
OK (not shorted) ??
YES
Replace G900 VCO
module
Issue 1 11/03
Is VCO output frequency 3900 MHz
YES
and output level > -10 dBm ??
Measure with high impedance
probe.
YES
Check loop filter components
(joints) C924,C926, C928 and
R910, R912 and balun T902.
Check DC-voltage for VR1B from
C912, is it ca. 4.7 V.
Check reference from VCTCXO
(19.2MHz) in C920.
OK ?
NO
Fix T902.
Figure 25: WCDMA TX Synthesizer troubleshooting
Nokia Corporation.
Troubleshooting instructions
NO
NO
I - if VR1B is e.g. 0 V, then UEM
and connection into it must be fixed.
- Otherwise components around
G900 needs to be fixed.
- if this doesn't help change N900
(TEX)
Check N950
( Ext.Reg1). Measure
from R940, is the
TXVCOPwr enable ON.
NHM-1
YES
Synthesizer OK
YES
Replace G900 VCO
module
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