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

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RF Description and Troubleshooting Nokia Customer Care
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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
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Transmitter Block Diagram
Following is the block diagram for the Tx RF system. I
Figure 2: Tx system block diagram
TP1
TP2 TP3
TP4

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Transmitter Schematics
The following schematics are for general reference only. See the Schematics chapter for detailed versions.
Figure 3: Transmitter schematic 1

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Figure 4: Transmitter schematic 2

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RF Description and Troubleshooting Nokia Customer Care
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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
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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.

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RF Description and Troubleshooting Nokia Customer Care
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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).

Nokia Customer Care RF Description and Troubleshooting
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Figure 9: The output of the mobile terminal on a spectrum analyzer should look like the figure on the left
If using the AAS-10 probe with the phone connected to the call box, the amplitude
should be approximately -7 dBm at the antenna test point on the top of the PWB.
Good output Bad output

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Tx RF Test Points
Figure 10 and Figure 11 are the transmitter DC/RF test points. See Table 1 on page 14 for
test point descriptions and values.
Figure 10: Tx DC/RF test points - PA section
3
214
9
TP12
TP13
TP4
TP3
TP11
PNMIC
DC-DC

Nokia Customer Care RF Description and Troubleshooting
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Following are the Tx DC/RF test points for the N7000 Tx Section
Figure 11: Tx DC/RF test points - N7000 section
3
214
TP5
TP7
TP8
TP3
TP2
TP9
TP6
TP10
TP91
Tx SAW
N7000 Tx

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Table 1 shows the Tx DC/RF test points to probe (see Figure 10 and Figure 11) when
troubleshooting the cell transmitter path. It is recommended that you follow the steps in
order.
Table 1: Tx DC test points
Test Point FUnction
Typical Value/
Frequency
HP85024A
Typical Value/
Frequency
Prod Probe
Comments
TP1 Z7000
pin 1
N7000 - Out -40 dBm/ 1MHz
836.52MHz
-13.2dBm/
836.52MHz
Output of N7000 Driver,
Input to Tx SAW Filter
TP2 Z7000
pin 3
PA - In -26 dBm/ 1MHz
836.52MHz
-15.4 dBm/
836.52MHz
Output of Tx SAW,
Input to PA
TP3 Z7400
In
PA - Out 5.0 dBm/ 1MHz
836.52MHz
18.3 dBm/
836.52MHz
Input to Isolator
TP4 Z7400
Out
Iso - Out 2.5 dBm/ 1MHz
836.52MHz
10.3 dBm/
836.52MHz
Output of Isolator,
Input to Duplexer
TP5 C7002 IF - Out -29 dBm/ 1MHz
228.6MHz
-24 dBm/
228.6MHz
Tx IF probing point at IF
filter
TP6 VR5 2.75V dc VHF VCO/PLL, IQ modulator
supply from UEM
TP7 VR7 2.75V dc UHF PLL supply from UEM
TP8 VR2 2.75V dc Mixer, driver, and IF supply
from UEM
TP9 R7002
TP91 R7001
VAGC-RF
VAGC-IF
0.2 to 1.8V dc Tx AGC control voltage
from UPP.
0.2V = Max Gain
1.8V = Min Gain
TP10 VIO-Tx 1.8V Supply for digital circuits
from UEM
TP11 VBAT 3.2V dc Battery voltage (nominal
voltage 3.7V dc)
TP12 VCC 3.1V dc (High Gain) Main PA supply voltage
from PMIC.
Lgain=0.8V, Mgain=1.25V,
Hgain=Vbat
TP13 C7407 VG/Vref 4.6V dc (Enable) PA gate voltage (Enable/
Disable). Disable=0V

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Tx AGC Tuning
Tx power versus IF/RF PDM can be verified against FlaLi specification limits. Make sure
that the PA is set in high gain mode (GenIO bits 10, 13, and 12 are set to H).
*Not an actual FlaLi tuning PDM. PDM produces approx. 25 dBm at the antenna connector.
Table 2: Tx AGC Tuning Steps
Tx Tuning
AGC Step
Target
Power
Low
Limit
High
Limit
Tx AGC (0) -46 -55 -37
Tx AGC (1) -24 -34 -14
Tx AGC (2) -15 -25 -6
Tx AGC (3) -4.5 -14 5
Tx AGC (4) 2.5 -7 12
Tx AGC (5) 6 -3 15
Tx AGC (6) 15 6 24
Tx AGC (7)* 25 21 27

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Receiver Troubleshooting
Following is the Rx system block diagram.
Figure 12: Receiver system block diagram
LNA SW Control
RFA
VHF PLL
367.2 MHz
2
÷
I/Q Down
Converter CDMA
BB Filter
BB AMP
CDMA
BB Filters
Duplexer
LNA
SAW
CELL
UHF Synthsizer
JEDI
Bias and Control
VCTCXO
Reference Clock
To Base-Band
To BB
UHF VCO
1052.61-1077.57
Loop Filter
IFA IF SAW VGA
Antenna
AFC
BB AMP
TX
N7160 IC N7100 IF IC

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Receiver Schematics
The following schematics are for general reference only. See the Schematics chapter for detailed versions.
Figure 13: Receiver schematic 1
RF SAW filter
CDMA IF Out 183.6 MHz
Lo in
LNA Input
LNA Gain Control
Mixer Output 183.6 MHz

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.
Figure 14: Receiver schematic 2

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Turning on the Rx Path
Use the following steps to turn on the Rx path using Phoenix.
1. Turn on Receiver Only in CDMA mode.
2. On the Phone Control dialog box, click the LOCAL button in the Phone State
area to put the phone into Local Mode.
Figure 15: Phone Control dialog box
3. Click Execute.
4. On the RF Main Mode dialog box select the following values:
•Band = Cell (CDMA)
•Channel = 384
•Mode = Rx/Tx
5. Click Set.
Figure 16: RF Main Mode dialog box for Cell Mode
Note: Be sure that the “RF Main Mode set successfully” message appears in the status bar

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Switching the Rx Gain, IF, and IP States
Use the RF Gen I/O dialog box to switch the gain state (Hi and Lo) for CDMA mode.
Select the desired state, and click Refresh.
• Lo Gain Mode: Move the green square to No Gain.
• High Gain Mode: Move the green square to Gain.
Figure 17: RF Main Mode dialog box for Cell Switching Rx Gain States
MIN MIN
MAX MAX