Nokia 7270 Service Manual
RM-8/RM-47/RM-48
Nokia Customer Care
67
COMPANY CONFIDENTIAL
Issue 2 03/2005
Copyright © 2005 Nokia. All Rights Reserved.
Fault Finding Chart for GSM850 Transmitter
In following, it is assumed that the TXP signal is used as trigger-signal. For that a TXP test point is pro-
vided.
vided.
Figure 13: GSM850 troubleshooting, GMSK
Use Phoenix to select
TX_Data Type: "1" or "0"
TX Power Level: 10
Ch190
Ensure Vbatt=3.9 V
Yes
Oscilloscope
R7707
Mode
Vdc = 0 Volt
R7511
VREF01
Vdc = 1.35 Volt
Check
C7512
VR2
Vdc = 2.78 Volt
No
Base Band
TXP testpoint J7504
TXP
Vdc = 1.8 Volt
C7520
VR5
Vdc = 2.78 Volt
C7526
VR3
Vdc = 2.78 Volt
Yes
Oscilloscope
C7529
TXIOUTP
67kHz
Vac = 0.4 Vpp, Vdc = 1.1 V
No Check
C7529
TXIOUTN
67kHz
Vac = 0.4 Vpp, Vdc = 1.1 V
Base
Band
C7530
TXQOUTP
67kHz
Vac = 0.4 Vpp, Vdc = 1.1 V
C7530
TXQOUTN
67kHz
Vac = 0.4 Vpp, Vdc = 1.1 V
Yes
Oscilloscope
C7701
VTXB_850
Vdc = 2.88 Volt
No
Check:
VC1
CONT1
Vdc = 0 Volt
Helgo Serial Interface
VC2
CONT2
Vdc = 0 Volt
Helgo
VC3
R7715
CONT3
Vdc = 2.76 Volt
C7701
VPCTRL_850
Vdc > 1.3 Volt
Yes
Spectrum analyzer
No
Check
Z7700 out, R7705 in
RFin_850/900
P>= -3 dBm, 836.6MHz
EGSM TX SAW Filter
Compare with good sample
Helgo
Yes
Synthesizer
Use Phoenix to select
TX_Data Type: Random
TX Power Level: 10
Yes
Spectrum analyzer
Check PA N7700
Z7800 TX1 (PA
N7700RFOut_850/900)
No
Check Power Loop
Power = +25 dBm, 836.6MHz
Check TXC
Yes
GSM850 TX
OK
OK
C7532
CONT3
Vdc = 2.76 Volt
VPCTRL_850
Vdc > 1.3 Volt p-p