NHL-10
RF Troubleshooting CCS Technical Documentation
ISSUE 2 01/2004 COMPANY CONFIDENTIAL 29
Copyright © 2003 Nokia. All Rights Reserved.
Fault-finding chart: RF side of transmitter
Measure power at RF connector:
GSM900: Power between 31 & 35dBm
GSM1800 & GSM1900: Power between 28 & 32dBm
Transmitter is OK
Check all
power levels
OK
OK
Tune TX power
OK
NOK NOK
Check power
control loop
Signal found?
No
Search for output signal with
500MHz span. Signal found
on incorrect frequency?
Yes
NOK
Yes
Correct signal at
ASM output?
Yes
RF connector broken?
No
Correct signal at
ASM input?
Yes
ASM broken?
Correct signal at
directional coupler
input?
No
Yes
directional coupler broken?
Yes
No
Correct signal at
power amplifier
input?
power amplifier broken?
Yes
Check power
control loop
OK
No
EGSM => check pre-amp & SAW
DCS/PCS => check balun
OK
Check bias network at output of Mjolner IC
(Discrete components: R's, L's & C's)
OK
Check fault finding chart of
TX-BB interface
OK
Mjolner broken?
Replace it & retune RF
In Phoenix select:
Active unit=TX, Operation Mode=Burst, TxPA Mode=Free,
TxData Type=Random, and for each band:
GSM900, channel=37, PL5
GSM1800, channel=700, PL0
GSM1900, channel=661, PL0
Check power
control loop
OK
Trouble-shoot
synthesizer
Note:
When using the SA to check if a signal is 'correct' at a certain
point (at input/output of ASM, directional coupler, PA, SAW-
filter, balun, etc.), the best way to do so is to compare with the
signal of a working sample of a phone. The reason for this is
that the level seen on the SA screen will vary depending on the
type of probe, the impedance of the measurement point, etc.
Check power
control loop
Using the oscilloscope, check power control loop signals
(Compare to oscilloscope screen plots shown below)
Line
Testpoint
VBD R801
DET R802
VPD_900 R818
VBD
DET
VPD_900
PA
EGSM
input
PA
DCS/PCS
input
PA
DCS/PCS
output
PA
EGSM
output
ASM
DCS/PCS
input
ASM
EGSM
input
EGSM
SAW
output
Balun
DCS/PCS
output
ASM
TX
output
VPD_1800
VTXB_900
(pre-amp bias)
VBD: bias to pwr detector
2.7V
4.615ms
VPD_900: input voltage ctrl signal to PA
GSM900, PL=5
DET: output of pwr detector
GSM900, PL=5
Spectrum analyzer screen shots
Measurements done at RF connector
Span = 3MHz
Span = 0Hz
EGSM900
channel = 37
PL = 5
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