Nokia 6255 Service Manual 10rm19rf

Nokia Customer Care

6255/6255i/6256/6256i (RM-19)

Mobile Terminal

RF Description and

Troubleshooting

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Contents Page

Introduction ..................................................................................................................................................... 5

Mobile Terminal Components ..................................................................................................................... 6

Main PWB ......................................................................................................................................................6

UI (Secondary) PWB ....................................................................................................................................8

Preliminary RF Troubleshooting............................................................................................................... 10

Mobile Terminal Cannot Make a Call ..................................................................................................10

Tx Power Low ..............................................................................................................................................10

Transmitter RF Troubleshooting .............................................................................................................. 11

Transmitter Block Diagram .....................................................................................................................12

Transmitter Schematics ...........................................................................................................................13

Transmitter Troubleshooting Setup ......................................................................................................15

AMPS Tx Setup ....................................................................................................................................... 15

Cell Tx Setup ........................................................................................................................................... 18

PCS Setup................................................................................................................................................. 20

Transmitter RF Troubleshooting Procedures ......................................................................................22

Failed Test: Tx PA Detector ................................................................................................................. 23

Tx Output Spectrum.............................................................................................................................. 24

Tx DC Test Points - Bottom Side ....................................................................................................... 25

Tx DC and RF Test Points - Top Side................................................................................................. 26

Tx RF Test Points - Bottom Side........................................................................................................ 28

RF Power Supply DC Test Points - Bottom Side............................................................................ 29

Receiver RF Troubleshooting .................................................................................................................... 31

Receiver Block Diagram ...........................................................................................................................32

Receiver Schematics .................................................................................................................................33

RF AGC Status ............................................................................................................................................35

Turning on the Rx Path ............................................................................................................................36

Switching the Rx Gain States ................................................................................................................38

Checking AMPS from RF to IQ ........................................................................................................... 38

Checking Cell Receiver from RF to IQ.............................................................................................. 39

Checking PCS Receiver from RF to IQ.............................................................................................. 41

Receiver Diagnostic Signal Tracing ......................................................................................................42

Receiver DC Test Points........................................................................................................................ 43

Receiver RF Test Points ........................................................................................................................ 44

Receiver IF Test Points.......................................................................................................................... 45

Receiver Logic Input Voltages ................................................................................................................46

N7160 Receiver Overview .......................................................................................................................47

Synthesizer Troubleshooting .................................................................................................................... 49

Synthesizer Block Diagram .....................................................................................................................50

Synthesizer Schematics ...........................................................................................................................51

Synthesizer Troubleshooting Setup ......................................................................................................52

Incorrect PLL Frequencies.................................................................................................................... 52

VCTCXO Troubleshooting .........................................................................................................................53

VCTCXO Manual Tuning....................................................................................................................... 54

AFC Voltage Troubleshooting .................................................................................................................55

UHF Synthesizer .........................................................................................................................................56

UHF Synthesizer Test Points ............................................................................................................... 57

Rx VHF LO (N7100) Schematic ..............................................................................................................58

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

Rx VHF LO Troubleshooting ....................................................................................................................59

Tx UHF LO (N7000) Schematic ..............................................................................................................60

Tx UHF LO (N7000) Troubleshooting ....................................................................................................61

GPS Troubleshooting................................................................................................................................... 62

GPS RF Block Diagram .............................................................................................................................62

GPS RF Schematic .....................................................................................................................................63

GPS Troubleshooting Setup ....................................................................................................................64

Self Test Failure...................................................................................................................................... 65

Oscillator Failure.................................................................................................................................... 65

CW Test Failure....................................................................................................................................... 65

GPS RF Troubleshooting....................................................................................................................... 65

GPS DC Test Points................................................................................................................................ 66

GPS RF Test Points................................................................................................................................. 69

FM Radio Troubleshooting ........................................................................................................................ 71

FM Radio Schematic .................................................................................................................................71

FM Radio Troubleshooting Setup ..........................................................................................................72

FM Radio Part Layouts and Probe Points........................................................................................ 72

Bluetooth Troubleshooting ....................................................................................................................... 75

Bluetooth Schematic ................................................................................................................................75

Bluetooth Troubleshooting Setup .........................................................................................................76

Bluetooth Troubleshooting Flowchart ............................................................................................. 77

Bluetooth DC and RF Test Points ...................................................................................................... 78

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

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6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

Introduction

When troubleshooting the receiver, first check the RX_AGC PDM value. The AGC value should be close to the typical values in the tables. The RX AGC tries to keep a constant amplitude at the output of the receiver chain; if the AGC value indicates an AGC gain that is substantially higher than normal, the AGC is compensating for extra loss in another component. If the AGC PDM values are normal and there is still a problem, check the actual AGC voltages. RF probing at specific locations in the chain can then help to pinpoint the source of the problem.

Likewise, when troubleshooting the transmitter, first check the measured output power and AGC values, which give an indication of where to start probing.

Although probing points and signal-level information are given for each point in the receiver and transmitter chains, the troubleshooter is not expected to probe each point on every mobile terminal — only the suspected trouble spots.

Absolute power measurements were made with an Agilent (HP) 85024A active highimpedance probe. Other probes can be used (but should be high-impedance so that the measurement does not load the circuit) but may very well have a different gain; therefore, adjust the absolute measurements accordingly. Also, adjust if using a probe attenuator.

Where a range is given for loss, typically the higher loss occurs at the band edges. Probing is not a very accurate method to measure absolute power; therefore, you cannot expect measured results to exactly match the numbers listed.

Power depends on the impedance of the circuit. For example, if a filter has a nominal loss of 5dB, then straightforward probing on the input and output, then subtracting, might not result in 5dB because the input impedance might be different from the output impedance. Most components in the RF section have the same input and output impedance (50ohms), but where this is not the case absolute power is noted in dBm, rather than loss or gain in dB.

When testing the CDMA receiver, it is easier to inject a CW tone into the receiver. The gains and losses are the same for a CW signal as for CDMA.

Note: After opening the shield lids, always replace them with new lids.

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Mobile Terminal Components

The mobile terminal includes two PWB boards, the main PWB and the UI PWB.

Main PWB

Following are the components of the main PWB.

Tx I/Q signal test points

Tx power detector

Rx I/Q signal test points

Figure 1: Main PWB component layout - top

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

Cell coupler

Diplexer

Antenna connector

VCO

PCS PA

Cell PA

Cell Tx filter

PCS Tx filter

N7000: Tx Upconverter

PCS coupler

Cell duplexer

PCS duplexer

Synthesizer IC

Headset jack

Rx RF Cell filter

N7160: Rx front-end

Rx RF PCS filter

Rx IF AMPS filter

VCTCXO

Rx IF CDMA filter

N7100: Rx downconverter

FM radio IC

D2800 processor

Flash

Tomahawk connector

UEM

Bluetooth IC

Figure 2: Main PWB component layout - bottom

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

UI (Secondary) PWB

Following are the components of the UI PWB.

GPS ceramic filter

GPS LNA

GPS SAW filter

Figure 3: UI PWB component layout - top

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

GPS antenna connector

GPS RF IC

GPS BB IC

GPS ceramic antenna

GPS antenna matching circuitry

GPS 16.368 MHz TCXO

Figure 4: UI PWB component layout - bottom

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

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 Read Parameters 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

7. The transmitter and receiver are working properly in Local Mode. See

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

3. Look for the presence of a Tx signal on a spectrum analyzer at the correct

page 54.

"Transmitter RF Troubleshooting" on page 11 and "Receiver RF Troubleshooting" on page 31 for detailed information.

proper placement, rotation, and soldering of components.

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. (See "Tx RF Test Points - Bottom Side" on page 28.)

4. Ensure that the power supplies to the Tx have the correct voltage. (See "Tx DC Test Points - Bottom Side" on page 25)

5. Ensure that the AGC PDMs are set for the desired Tx power and that the AGC voltages are correct. (See "AMPS Tx Setup" on page 15, "Cell Tx Setup" on page 18, or "PCS Setup" on page 20.)

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Transmitter RF Troubleshooting

Following are the main Tx RF components.

Antenna connector

Diplexer

Cell coupler

PCS coupler

TOP SIDE

PCS Tx SAW filter

Cell PACell Tx SAW filter

PCS PA

BOTTOM SIDE

Power detector

Power switch

PCS duplexer

Cell duplexer

Figure 5: Main transmitter RF components

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Transmitter Block Diagram

Following is the block diagram for the Tx RF system.

N7000 Tx IC

Figure 6: Tx system block diagram

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Transmitter Schematics

The following schematics are for general reference only. See the Schematics chapter for detailed versions.

Cell Tx filter

N7000 Tx IC

PCS Tx filter

Tx LO lock voltage

Loop filter

Figure 7: Transmitter schematic 1

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

PCS PA

Component changes based on PA manufacturer

Cell PA

PCS duplexer

Diplexer

Couplers

Power detector

Cell duplexer

Figure 8: Transmitter schematic 2

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

Transmitter Troubleshooting Setup

Use the following sets of procedures to troubleshoot the transmitter using Phoenix. Due to the compact layout of the mobile terminal, some of the major test points are not accessible without destroying the shield frames and the EL lamp. For example, duplexers/ diplexer/couplers test points are blocked by the test jig, the PA test points are underneath the shield frame, and the BBIQ points are underneath the EL lamp.

To minimize effort, check the following in order:

1. Tx power at the RF connector.

2. All Tx DC points.

3. All soldering jig points for the whole Tx chain.

4. UHF LO presence:

• If the UHF LO is present, check the N7000 output.

• If the UHF LO is not present, it is a synthesizer problem.

5. If there is no N7000 output:

6. If there are several failed mobile terminals with the same symptoms, it may be

Use the following sections to set up troubleshooting in Phoenix according to the band you are using:

• "AMPS Tx Setup" on page 15

• "Cell Tx Setup" on page 18

• "PCS Setup" on page 20

AMPS Tx Setup

Use the following procedures to prepare for AMPS Tx troubleshooting using Phoenix.

1. Connect the RF test connector to a spectrum analyzer.

2. Connect the mobile terminal to the PC via a test jig. (The bottom connector is a

a. Change the N7000.

b. If the problem persists, reflow the duplexers, diplexer, and couplers.

c. If the problem persists, change the PA.

necessary to break one to determine the cause.

USB port.)

3. Connect a power supply to the mobile terminal.

4. Open the Troubleshooting menu, and click Phone Control.

The Phone Control dialog box appears.

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

5. Click the LOCAL button in the Phone State area to put the mobile terminal into Local Mode.

Figure 9: Phone Control dialog box

6. Open the Troubleshooting menu, point to AMPS, and click AMPS Control.

The AMPS Control dialog box appears.

Figure 10: AMPS Control dialog box

7. Click the Tx Control tab.

8. In the Set Channel field, type 384.

9. In the Power Level field, type 5.

10. Select the Transmitter ON option, and click Execute.

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

11. Configure the spectrum analyzer using the following values:

• Center Frequency = 836.52 MHz

• Span = 100 MHz

• Amplitude = 20 dBm

• Attenuation = Auto

• BW = Auto

Table 1: RF PDM Values at Power Level 5

Description/Field Reference Value

AGC1 -512

AGC2 -31

AGC3 -400

Rx IF AGC -234

AFC +176

Pout at RF connector +14dBm

Current 400-500mA

Figure 11: RF PDM dialog box for AMPS

12. Click Read Phone to update the values.

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Cell Tx Setup

Use the following procedures to prepare for Cell Tx troubleshooting using Phoenix.

1. Connect an RF test connector to a call box.

2. Connect the mobile terminal to the PC via a test jig. (The bottom connector is a USB port.)

3. Connect a power supply to the mobile terminal.

4. On the Phone Control dialog box, click the LOCAL button in the Phone State area to put the mobile terminal into Local Mode. (See Figure 9 on page 16.)

5. Open the Troubleshooting menu, point to RF, and click RF Main Mode.

The RF Main Mode dialog box appears.

Figure 12: RF Main Mode dialog box for Cell Mode

6. Select the following values on the RF Main Mode dialog box:

• Band = Cell (CDMA)

• Channel = 384

• Mode = Rx/Tx

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.

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

The CDMA Control dialog box appears.

Do NOT select this option

Figure 13: CDMA Control dialog box for Cell Tx troubleshooting

9. Select the following values:

• State = Rho ON

• Band = Cell

• Radio Configuration = Mode 1: IS-95 Voice

Note: Do NOT select the Set default PDM values option

10. Click Execute.

11. Configure the spectrum analyzer using the following values:

• Center Frequency = 836.52 MHz

• Span = 100 MHz

• Amplitude = 20 dBm

• Attenuation = Auto

• BW = Auto

Table 2: RF PDM Values

Description/Field Reference Value

AGC2 -250

AGC3 -387

Pout at RF connector +20dBm

Current 500-600mA

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

PCS Setup

Use the following procedures to prepare for PCS Tx troubleshooting using Phoenix.

Figure 14: RF PDM Control dialog box for Cell band

12. Click Read Phone to update the values.

1. Connect an RF test connector to a call box.

2. Connect the mobile terminal to the PC via a test jig. (The bottom connector is a USB port.)

3. Connect a power supply to the mobile terminal.

4. Open the Troubleshooting menu, and point to Phone Control.

The Phone Control dialog box appears. (See Figure 9 on page 16.)

5. Click the LOCAL button in the Phone State area to put the mobile terminal into Local Mode.

6. Open the Troubleshooting menu, point to RF, and click RF Main Mode.

The RF Main Mode dialog box appears. (See Figure 12 on page 18.)

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

7. Select the following values on the RF Main Mode dialog box:

• Band = PCS (CDMA)

• Channel = 600

• Mode = Rx/Tx

8. Click Set.

Note: Be sure that the “RF Main Mode set successfully” message appears in the status bar.

9. Open the Troubleshooting menu, point to RF, and click CDMA Control.

The CDMA Control dialog box appears. (See Figure 13 on page 19.)

10. Select the following values on the CDMA Control dialog box.

• State = Rho ON

• Band = PCS

• Radio Configuration = Mode 1: IS-95 Voice

Note: Do NOT select the Set default PDM values option.

11. Click Execute.

12. Open the Troubleshooting menu, point to RF, and click PDM Control.

13. Configure the spectrum analyzer using the following values:

• Center Frequency = 1880 MHz

• Span = 100 MHz

• Amplitude = 20 dBm

• Attenuation = Auto

• BW = Auto

Table 3: RF PDM Values

Description/Field Reference Value

AGC2 -511

AGC3 -83

Pout at RF connector +23dBm

Current 700-800mA

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Figure 15: RF PDM Control dialog box for PCS band

14. Click Read Phone to update the values.

Transmitter RF Troubleshooting Procedures

After Phoenix is set up using either the AMPS, Cell, or PCS setup procedures, use the following steps to troubleshoot the transmitter.

1. Using a voltmeter, check to see that all VR2, VR6, and VR1B are on the transmit system. (See "Tx DC Test Points - Bottom Side" on page 25.)

• If any are missing, look for SMD problems around the N7000 and the UEME.

• If SMD is good, replace the UEME.

2. Once all DC voltages are present, check the AGC control voltages. (See "AMPS Tx Setup" on page 15, "Cell Tx Setup" on page 18, or "PCS Setup" on page 20.)

• If the voltages are incorrect, check the SMD around TX_AGC1 and TX_AGC2.

• If the SMDs are correct, replace the D2800.

3. Using an oscilloscope, check the input modulation BBIQ wave forms at R7021, R7022, R7023, and R7024. They should all be present with an AC swing of about 500mVpp, with an offset of +1.2V.

• If one or more waveforms are missing, look for SMD problems around these

resistors.

• If the SMD is good, replace the UEM.

6255/6255i/6256/6256i (RM-19)

Nokia Customer Care RF Description and Troubleshooting

4. Use an AAS-10 RF probe to probe the Cell Tx output of the N7000.

• If there is no RF or low RF, look for SMD everywhere around the N7000.

• If the SMD is okay, replace the N7000.

5. Probe the PA input.

• If the level is low, look for an SMD issue on the Tx filter or matching

transformer (T7001 or T7002).

• Reflow or replace the filter as necessary.

6. Probe the PA output.

• If the RF is missing or low, look for Vbatt voltages and SMD issues on and

around the PA.

• If these are okay, replace the PA.

7. Probe the duplexer output.

• If the RF is missing or low, reflow or replace the duplexer.

8. Probe the coupler output.

• If the RF is missing or low, reflow or replace the coupler.

9. Probe the diplexer output.

• If the RF is missing or low, reflow or replace the diplexer.

Failed Test: Tx PA Detector

Use the following steps if you encounter a failed test for the Tx PA detector:

1. Use Phoenix to set the mobile terminal into Local Mode and activate the Tx with default output power.

2. The output power at the RF test connector should be 15dBm +/- 4dB. If not, follow the procedures in the "Transmitter RF Troubleshooting Procedures" section on page 22.

3. Using a voltmeter on DC, probe the detector output at C7313. The voltmeter should read approximately 1.4V. If not, replace N7300. (See page 26 for test point locations and common power and voltage variations.)

6255/6255i/6256/6256i (RM-19) RF Description and Troubleshooting Nokia Customer Care

Tx Output Spectrum

Following is the correct output of the mobile terminal on a spectrum analyzer with 100MHz span. Note that if you are using the AAS-10 probe with the mobile terminal connected to the call box, the amplitude should be approximately -7dBm at the antenna test point on the top of the PWB.

Figure 16: Correct output spectrum

Following is an example of incorrect output.

Figure 17: Incorrect output spectrum

+ 54 hidden pages

Nokia 6255 Service Manual 10rm19rf

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents Page

Introduction

Mobile Terminal Components

Main PWB

UI (Secondary) PWB

Preliminary RF Troubleshooting

Mobile Terminal Cannot Make a Call

Tx Power Low

Transmitter RF Troubleshooting

Transmitter Block Diagram

Transmitter Schematics

Transmitter Troubleshooting Setup

AMPS Tx Setup

Cell Tx Setup

PCS Setup

Transmitter RF Troubleshooting Procedures

Failed Test: Tx PA Detector

Tx Output Spectrum