Troubleshooting Chart For Gsm1800 Transmitter - Nokia RH-29 Series Manual

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Troubleshooting chart for GSM1800 transmitter

Is signal at
DCS
YES
DCS / PCS
Input of Z601
OK?
YES NO
Is VPD_1800
Replace signal OK?
L801
Are Z601
NO
Control lines
as per table?
YES
Replace
Check RF
Check
YES
Antenna
Connector
Switch
C650.
X602. OK?
NO
KEY
Replace RF
Connector. C650.
Test With
Spectrum
Analyzer
If the Tx output is too high, then it is most likely that there is a problem within the Power
Control loop.
Mjoelner is receiving the Reference TXC from Baseband and not getting any feedback
from DET to compare with TXC. The result is that Mjoelner drives VDP_900/VPD_1800
high to try and increase the power output so that the DET signal is matching TXC. With a
break in the Power Control loop, the DET signal never reaches Mjoelner so it assumes
that the PA is not outputting enough power so it tries to compensate by increasing the
gain.
When checking the Power Control loop, make sure that VBD is pulsing at 2.8V Peak to
Peak. Check the DET pulse at Mjoelner input on R706.
Issue 1 05/2004
Company Confidential
Is signal on
YES
Is TX Signal at
Is TX Signal at
C823 OK?
DCS / PCS In on
NO
R819 OK? L812 OK?
YES
Replace PA
NO
Investigate
YES
Mjoelner
Test With
Oscilloscope
Copyright © 2004 Nokia Corporation
Company Confidential
START
START
NO
Is TX Signal
at L705 OK?
DCS In on
Are TX I & Q
Signals OK?
YES
Are TXP &
TXC OK?
TXC TXP
U/S U/S
Change Change
UEM UPP
Check / End
Inspect Action
RH-29
6b - RF Troubleshooting
YES
Is Vr2 2.8V
on R720?
NO NO
NO
Check T701
Are Digital
& Associated
I & Q Signals
Components.
OK at J213 & J202
and J203?
J214
NO YES
Refer To Baseband
Fault Finding
YES
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