Nokia 2255 User manual
Nokia Customer Care
2255 (RM-97)
Mobile Terminal
ISSUE 1 10/2005 Company Confidential ©2005 Nokia Corporation
RF Description and
Troubleshooting
2255 (RM-97)
RF Description and Troubleshooting Nokia Customer Care
Page 2 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Contents Page
Mobile Terminal Components ..................................................................................................................... 4
Preliminary RF Troubleshooting.................................................................................................................. 5
Mobile Terminal Cannot Make a Call ....................................................................................................5
Tx Power Low ................................................................................................................................................5
Transmitter Block Diagram .......................................................................................................................6
Transmitter Schematics .............................................................................................................................7
Transmitter Troubleshooting ....................................................................................................................9
CELL Tx Setup............................................................................................................................................. 9
Failed Test: Tx PA Detector ................................................................................................................. 11
Tx RF Test Points ........................................................................................................................................13
Tx AGC Tuning ............................................................................................................................................16
Receiver Troubleshooting ........................................................................................................................17
Receiver Schematics .................................................................................................................................18
Turning on the Rx Path ........................................................................................................................ 20
Switching the Rx Gain, IF, and IP States ............................................................................................21
Receiver Troubleshooting ........................................................................................................................22
Receiver RF Troubleshooting Test Points ............................................................................................24
Receiver IF Troubleshooting Test Points .............................................................................................26
Cell Receiver Check from RF to IQ ........................................................................................................28
Receiver Diagnostic using Signal Tracing and Call Box.............................................................. 29
Rx Front-End IC (N7150) DC Troubleshooting ..................................................................................30
Synthesizer Troubleshooting ..................................................................................................................31
Synthesizer Block Diagram ................................................................................................................. 31
Synthesizer Schematic .............................................................................................................................32
Synthesizer Troubleshooting Setup ......................................................................................................33
19.2 MHZ VCTCXO Reference Clock .....................................................................................................35
VCTCXO Manual Tuning....................................................................................................................... 36
UHF Synthesizer Test Points ...................................................................................................................40
UHF Synthesizer Schematic ....................................................................................................................41
Incorrect UHF Frequency ..................................................................................................................... 42
Rx VHF ..........................................................................................................................................................43
Rx VHF Schematic .....................................................................................................................................44
Incorrect Rx VHF Frequency ............................................................................................................... 45
Tx VHF ...........................................................................................................................................................46
Tx VHF Schematic ......................................................................................................................................47
Incorrect Tx VHF Frequency................................................................................................................ 48
FM Radio Troubleshooting ......................................................................................................................49
Nokia Customer Care RF Description and Troubleshooting
2255 (RM-97)
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 3
Mobile Terminal Components
Figure 1 illustrates the main components of the 2255.
Figure 1: Component layout (bottom)
RF connector
Cell duplexer
Tx Up- converter
Cell Tx SAW
filter
Cell Tx PA
Rx Down- converter
UIM card
Cell Rx RF
SAW filter
Rx IC
VCO
RF IF CDMA filter
VCTCXO
UEM (BB)
UPP (BB)
PA PMIC
DC-DC
converter
Cell isolator
2255 (RM-97)
RF Description and Troubleshooting Nokia Customer Care
Page 4 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Preliminary RF Troubleshooting
The following sections identify steps to troubleshoot some common RF issues.
Mobile Terminal Cannot Make a Call
Verify the following if the mobile terminal cannot make a call:
1. The mobile terminal is in Normal Mode (i.e., the mobile terminal is searching for
a signal, net server is on).
2. The Preferred Roaming List (PRL) is loaded into the mobile terminal.
3. The mobile terminal is tuned and has passed tuning. Read the tuning parameters
using the Batch Tune component in Phoenix. An untuned mobile terminal has all
zeros in the tuning file.
4. The call box channel is set for a channel in PRL.
5. The SID is correct and entered into the mobile terminal.
6. The VCTCXO is centered as described in the "VCTCXO Manual Tuning" section on
page 34.
7. The transmitter and receiver are working properly in Local Mode. See
"Transmitter Troubleshooting" on page 8 and "Receiver
Troubleshooting" on page 16 for detailed information.
Tx Power Low
Complete the following steps if Tx power is low:
1. Use Phoenix to turn on the transmitter in Local Mode.
2. Perform a visual inspection of the PWB under a microscope to check for the
proper placement, rotation, and soldering of components.
3. Look for the presence of a Tx signal on a spectrum analyzer at the correct
frequency.
• If a signal is present but off-frequency, check the synthesizers for proper
frequency and amplitude. One of the synthesizers may be unlocked or the
VCO has no output signal.
• If a signal is not present or is present but is low in amplitude, check the
probing diagrams to determine where in the chain the fault occurs.)
4. Ensure that the power supplies to the Tx have the correct voltage.
5. Ensure that the AGC PDMs are set for the desired Tx power and that the AGC
voltages are correct.
2255 (RM-97)
Nokia Customer Care RF Description and Troubleshooting
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 5
Transmitter Block Diagram
Following is the block diagram for the Tx RF system. I
Figure 2: Tx system block diagram
TP1
TP2 TP3
TP4
2255 (RM-97)
Nokia Customer Care RF Description and Troubleshooting
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 6
Transmitter Schematics
The following schematics are for general reference only. See the Schematics chapter for detailed versions.
Figure 3: Transmitter schematic 1
2255 (RM-97)
RF Description and Troubleshooting Nokia Customer Care
Page 7 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Figure 4: Transmitter schematic 2
2255 (RM-97)
RF Description and Troubleshooting Nokia Customer Care
Page 8 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
Transmitter Troubleshooting
CELL Tx Setup
Use the following procedures to prepare for CELL Tx troubleshooting using Phoenix.
1. Connect RF test connector to a call box.
2. Connect the phone to a PC via the bottom connector, and connect a power
supply.
3. Open the Troubleshooting menu, and click Phone Control.
The Phone Control dialog box appears.
4. On the Phone Control dialog box, click the LOCAL button in the Phone State
area to put the phone into Local Mode.
Figure 5: Phone Control dialog box
5. Open the Troubleshooting menu, point to RF, and click CDMA Control. The RF
Main Mode dialog box appears.
6. Select the following values on the RF Main Mode dialog box:
•Band = Cell (CDMA)
•Channel = 384
•Mode = Rx/Tx
Nokia Customer Care RF Description and Troubleshooting
2255 (RM-97)
ISSUE 1 10/2005 ©2005 Nokia Corporation Company Confidential Page 9
Figure 6: RF Main Mode dialog box
7. Click Set.
Note: Be sure that the “RF Main Mode set successfully” message appears in the status bar.
8. Open the Troubleshooting menu, point to RF, and click CDMA Control.
The CDMA Control dialog box appears.
Figure 7: CDMA Control dialog box for Cell Tx troubleshooting
9. Select the following values on the CDMA Control dialog box.
•State = Rho ON
•Band = Cell
•Radio Configuration = Mode 1: IS-95 Voice
• Select the Set default PDM values check box.
10. Click Execute.
11. At this point you should be able to measure Tx Pout at the RF connector. The cell
band Tx Pout = 0 to 2 dBm. If you do not see these values, set the AGC PDM for
25 dBm and probe the Tx path to figure out where in the path the fault occurs.
12. Open the Troubleshooting menu, point to RF, and click PDM Control.
2255 (RM-97)
RF Description and Troubleshooting Nokia Customer Care
Page 10 ©2005 Nokia Corporation Company Confidential ISSUE 1 10/2005
The RF PDM Control dialog box appears.
Figure 8: RF PDM Control dialog box for Cell troubleshooting
13. Click Read Phone to update the values.
14. Configure the spectrum analyzer using the following values:
• Center Frequency = 836.52 MHz
• Span = 100 MHz
• Amplitude = 20 dBm
• Attenuation = Auto
• BW = Auto
Adjust the following PDM field values on the RF PDM dialog box:
• Set PA Gain State to High
• Adjust Tx RF AGC PDM to around –250
• Adjust Tx IF AGC PDM to around –250
• Set Output level to +23dBm on CH-384 and monitor the current between
590mA and 660mA.
Failed Test: Tx PA Detector
1. Use Phoenix to set the phone in Local Mode, and activate the Tx with default
output power. The output power at the RF test connector should read
9 dBm +/- 4 dB.
2. Use a voltmeter on DC, and probe the detector output at C813. The voltmeter
should read approximately 1.4 V. If not, replace the detector (N803).
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