Fault Finding Chart For The Receiver - Nokia 616 Service Manual

TFE-4/RV-1
TF4 Technical Information

Fault finding chart for the receiver

The phone layout does not have dedicated test points for the analogue differential RX I
and Q signals (RXIINP, RXIINN, RXQINP, RXQINN) from Mjoelner RF ASIC to UEM. The BB
part is used to measure those signals by means of RSSI reading. It is assumed that cor-
rect calibration of RSSI reading has been carried out. RSSIreading [dBm] = 20log(U
+ AGC
calibrated
Therefore, don't calibrate a defective phone before the phone error has been found.
When a defective phone has been calibrated, a possible error in RX front end might be
masked. In that case one can have a reasonable RSSI reading, although the front end
shows excessive losses. To rule this out do the following:
Check if AGC calibration is within limits
Check if SNR reading is OK.
Use an Oscilloscope to check levels of "RXIINN" and "RXQINN".
If RX and TX path are faulty it has to be checked that synthesizer is working. If it does,
then check path from RF connector X602 to antenna switch Z601 (see RX fault finding
"Check RXTX switch")
Make sure that
Synthesiser
is working
Apply -80dBm signal
from Generator
to Antenna Connector
phone: local, burst mode
EGSM,
Apply -92dBm signal
PCS, PCN
No
from Generator
RSSI reading
-80dBm to Antenna Connector
all bands
phone: local, burst mode
?
Yes
RX calibration
Calibrtion.
No
witin
limits
?
Yes
Rx chain
functional
2
= to be done in all 3 bands = to be done in
defective band only
Rx Signal paths
The signal paths of the receiver are shown in following block diagram. Note that the pic-
Page 8b-52
Company Confidential
RX Fault finding
T
Note: RF levels given in that chart are dependent on RF probe and must be validated with a known good sample
RSSI
EGSM,
and SNR Yes
PCS, PCN
No
wrong in all 3
SNR measurement
bands
all bands
?
o.k.
?
Yes
No
Change generator level
to -55dBm
phone: local,
continous mode
Check
RxTx Switch
SA
SA
Z601
Yes
Z601
Rx output
EGSMout
(900,1800,1900)
-76dBm
> -75dBm
?
No
Change
Z601
= to be done only once
(common for all bands)
Copyright © 2005 Nokia Corporation.
Company Confidential
Nokia Customer Care
Osci: Osci:
SA SA
RF-BB Yes RX I/Q
Z601 Z601 Yes
serial level
EGSMout EGSMout
o.k.
Interface
-76dBm -76dBm
?
o.k.
?
No No
BB Error Change
Check UPP Mjolner
Check
Check
Bias
SAW
SA
Osci:
SA
SA
Z604,Z602,Z603
LNA bias
Yes Yes
Z601
Z601
SAWout
(VR6)
EGSMout
EGSMout
both lines
=2.8V
-76dBm
-76dBm
>-78dBm
?
?
No
No
Change
Check
Z604,Z602,Z603
C620, C632
and
BB (UEM)
)
BB
BB Error
Check UEM
Check
Check
Yes
Bias
LNA
Osci: SA Osci: SA
RX -BB bias
Z601 LNA Z601
Yes
(VR4) base voltage
EGSMout EGSMout
=2.8V
-76dBm -76dBm = 0.8V
? ?
No No
Change
Check
Mjolner
C871
and
BB (UEM)
Issue 2.0 Mar/2005