Nokia 6020b Service Manual 06(b) rm31 rf trouble

Nokia Customer Care

6(b) - RF Troubleshooting

Instructions

Issue 1 03/2005 COMPANY CONFIDENTIAL

RM-31

Nokia Customer Care 6(b) - RF Troubleshooting Instructions

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6(b) RF Troubleshooting Nokia Customer Care

Table of Contents

Page No

General Information on RF Troubleshooting ................................................... 5

Test environment ............................................................................................... 5

Test conditions................................................................................................... 5

Receiver Verification and Troubleshooting...................................................... 7

General instructions for RX troubleshooting ...................................................... 7

Measuring RX I/Q signals using RSSI reading .................................................. 7

Measuring RX performance using SNR measurement .................................... 8

Measuring front-end power levels using spectrum analyzer .......................... 10

Measuring analogue RX I/Q signals using oscilloscope ................................ 10

Fault finding chart of the receiver..................................................................... 11

Transmitter ........................................................................................................ 18

General instructions for TX troubleshooting..................................................... 18

GSM850 transmitter......................................................................................... 18

General instructions for GSM850 TX troubleshooting ................................... 18

Fault finding chart for GSM850 transmitter .................................................... 20

GSM1800 transmitter....................................................................................... 22

General instructions for GSM1800 TX troubleshooting ................................. 22

Fault finding chart for GSM1800 transmitter .................................................. 24

GSM1900 transmitter....................................................................................... 26

General instructions for GSM1900 TX troubleshooting ................................. 26

Fault finding chart for GSM1900 transmitter .................................................. 28

Synthesizer ........................................................................................................ 31

General instructions for synthesizer troubleshooting ....................................... 31

Checking synthesizer operation....................................................................... 31

Fault finding chart for PLL synthesizer............................................................. 34

Frequency tables ............................................................................................. 36

GSM850 ......................................................................................................... 36

GSM1800 ....................................................................................................... 37

GSM1900 ....................................................................................................... 38

DC Supply Voltage Check ................................................................................ 39

Receiver test points ......................................................................................... 42

Transmitter test points ..................................................................................... 44

Synthesizer test points..................................................................................... 47

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Nokia Customer Care 6(b) RF Troubleshooting

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6(b) - RF Troubleshooting Nokia Customer Care

General Information on RF Troubleshooting

Notes:

Several bills of material (BOM): There are two different kinds of VCOs, VCTXOs, RF-PAs, SAWfilters and Antenna Switches (ASM) assembled. They may only be replaced with the same type as the original component (from the same manufacturer).

Phoenix version: In this document there are example measurements being depicted with pictures of AMS-Phoenix, version A 2004.06.1.69. In later versions pictures of menus and windows may look differently.

Layout version: The drawings of test points and component placement in this version of the document are taken from build B4.0 layout (1gqa_41a). If you use the document for newer layout versions, make sure to use the corresponding assembly and test point drawings.

■ Test environment

It is assumed, that the phones are disassembled and tested with a repair jig MJ-22R.

The following measurements have to be done for repairing the phone boards:

• RF measurements shall be done using a spectrum analyzer together with a highfrequency probe. Note that the signal will be significantly attenuated. Correct attenuation can be checked using a “good” phone board for example.

• LF (low frequency) and DC measurements shall be carried out with an oscillo- scope together with a 10:1 probe.

• For receiver measurements, a signal generator specified for frequencies up to 2000 MHz is required. The signal generator is connected to the antenna port of the repair jig. Most of the radio communication testers, like CMU200, can be used as a signal generator, but make sure to have a continuous (CW) signal without modulation for alignment purposes.

• Transmitter output level measurements shall be done with a power meter which is connected to the antenna port of the repair jig.

Always make sure that the measurement set-up is calibrated when measuring RF parameters at the antenna port. Remember to put the correct losses of the module repair jig and the connecting cable in Phoenix or in the set-up programs of the RF generators when realigning the phone.

Apart from key-components described in this document, there are a lot of discrete components (resistors, inductors and capacitors) for which troubleshooting has to be done by checking its proper soldering and complete assembly on the PWB. Capacitors and resistors can be checked by means of an ohm-meter, but be aware in-circuit measurements should be evaluated carefully.

■ Test conditions

Rx tuning of the 26 MHz reference oscillator (VCTCXO) is temperature sensitive because of the estimations of <AFC_value> and <AFC_slope>. According to the Production Test Specification DCS02294-EN-0.5, the ambient temperature has to be within a temperature range of 22°C to 28°C.

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Most RF semiconductors are static discharge sensitive. ESD protection must be taken into account during repair (ground straps and ESD soldering irons).

The RF ASIC Helgo is moisture sensitive. Therefore, the ASIC must be pre-baked prior to soldering.

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Receiver Verification and Troubleshooting

■ General instructions for RX troubleshooting

Connect the phone to a PC, which has Phoenix Service Software and a dongle installed, using either

• repair jig and DAU-9S (RS232) cable or

• repair jig and XCS-4 cable via FPS-8 Flash Box or

• DAU-9T cable (RS232).

Connect the phone to a power supply (DC voltage: 3.6V, max. current: 3A) and an RF signal generator. Switch the phone on.

Start Phoenix Service Software and open FBUS connection.

Select Scan Product Ctrl-R

and wait until the phone information (RM-31) is shown in the lower right corner of the screen.

Follow the instructions below.

■ Measuring RX I/Q signals using RSSI reading

Start Phoenix Service Software and open FBUS connection.

Select Scan Product Ctrl-R

Wait until the phone information is shown in the lower right corner of the screen.

Set the operating mode to local mode

Select Testing T

RF Controls F

Select Band GSM850 or GSM1800 or GSM1900

Active unit RX

Operation mode Burst

RX/TX Channel 190 or 700 or 661

Select Testing T

RSSI reading

In the RSSI Reading window, the <measuring mode> shall be set on Sum vector and the <reading mode> on Continuous.

The set up should now look like this:

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(The example below shows a screen shot in GSM900!)

Make the following settings on your signal generator:

Frequencies:

• GSM850: 881.66771 MHz (channel 190 + 67.710 kHz offset)

• GSM1800: 842.86771 MHz (channel 700 + 67.710 kHz offset)

• GSM1900: 1960.06771 MHz (channel 661+ 67.710 kHz offset)

RF power level:

• – 80 dBm @ the antenna connector of the phone/ test jig (remembering to compensate for the cable and jig attenuation).

Click on <Read now> in RSSI reading.

The resulting RSSI level shall be – 80 dBm +/– 0.5 dB in each band.

Measuring RX performance using SNR measurement

Start Phoenix Service Software and open FBUS connection.

Select Scan Product Ctrl-R

Wait until the phone information is shown in the lower right corner of the screen.

Set operating mode to <local mode>.

Select Testing T

RF Controls F

Select Band GSM850 or GSM1800 or GSM1900

Active unit RX

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Operation mode Burst

RX/TX Channel 190 or 700 or 661

Select Testing T

SNR Measurement M

Select Measuring mode Fast SNR (Radio Button)

Press Start

The window <Signal Measurement> pops up informing on frequency and power level of the signal generator to be set. Follow the command <Turn ON the RF generator>.

Press <ok> and the window will close.

Read the SNR result from the window SNR Measurement. The value shall exceed:

• GSM850: > 20 dB

• GSM1800: > 18 dB

• GSM1900: > 18 dB

The set up should now look like this:

(The example below shows a screen shot in GSM900!)

Choose the remaining GSM bands and measure accordingly the procedure described above.

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Measuring front-end power levels using spectrum analyzer

Spectrum analyzer (SA) level values depend on the probe type and shall be verified by a properly working phone sample. The levels that are given in this document are measured with a resistive probe (50 Ohm semi-rigid cable).

Start Phoenix Service Software and open FBUS connection.

Select Scan Product Ctrl-R

Wait until the phone information is shown in the lower right corner of the screen.

Set <operating mode> to <local mode>.

Select Testing T

RF Controls F

Select Band GSM850 or GSM1800 or GSM1900

Active unit RX

Operation mode Continuous

RX/TX Channel 190 or 700 or 661

Please refer to the fault finding chart and Appendix for proper levels at different test points.

Measuring analogue RX I/Q signals using oscilloscope

Measuring with an oscilloscope RX I and RX Q signals on the test points <RXI> respectively <RXQ> is recommended only if the RSSI reading does not provide enough information. Input level = -60dBm.

Start Phoenix Service Software and open FBUS connection.

Select Scan Product Ctrl-R

Wait until phone information is shown in the lower right corner of the screen.

Set operating mode to <local mode>.

Select Testing T

RF Controls F

Wait until the RF Controls

window pops up.

Select Band GSM850 or GSM1800 or GSM1900

Active unit RX

Operation mode Continuous

RX/TX Channel 190 or 700 or 661

AGC 10

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The following picture should be displayed on an oscilloscope's screen if the receiver is working properly:

Signal amplitude 1.40Vpp

DC offset ª 1.28V as the offset is floating, switch to the operating mode

<Burst> in Phoenix and read the DC offset

Frequency 67kHz

■ Fault finding chart of the receiver

During fault finding, the calibration procedure is used to find out, whether all bands are affected (error in common part of the Rx chain) or only one band (error in a Rx part of the failed band).

Take care not to save calibration values to the phone memory, which are out of limits. Find the error first and repair it.

When a defective phone has been calibrated, a possible error in RX front-end might be masked. In that case, one can get a reasonable RSSI reading, although the front-end shows excessive losses. If it is not sure that incorrect re-calibration has been made, following steps shall be carried out:

• Check if AGC calibration is within limits.

• Check if SNR reading is o.k.

Use an oscilloscope to check levels of “RXI” and “RXQ”.

The RF ASIC generates only single ended I and Q signals (RXI, RXQ). As the A/D converter in UEM requires two differential signals, an artificial mid voltage is generated from VrefRF02. The phone layout has dedicated test points for the analogue RX I and Q signals (J512, J513).

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The BB part is used to measure those signals by means of RSSI reading. This works only if correct calibration has been carried out in production.

RSSIreading [dBm] = 20log(U

BB/ULSB

) - AGC

calibrated

In order to check the levels and frequencies of RF signals, the following probe can be used (note that only the core lead contacts the test point, the shielding of the coaxial cable does not contact GND during the measurement):

Connect this probe via a coaxial cable and a DC block to a spectrum analyzer. The DC block is important to protect the spectrum analyzer from DC levels, which superpose the RF signal at several test points.

If both RX and TX path seem to be faulty, it has to be checked if the synthesizer is working.

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Phoenix:

Phone: local mode

Open

Signal Generator:

Phoenix:

Open Check RSSI Level = -80dBm

Execute Rx Calibration in selected band, refer to chapter 9.2.1

re calibration results within limits?

Make sure that

Synthesizer is working

Yes

All 3 bands

RF Controls

Active Unit: Rx Op. Mode: Burst Rx/Tx channel: default (mid)

Level: –80dBm Frequency: calculated from Phoenix + 67.71kHz

RSSI reading

see

Yes next bandNo

Synthesizer Fault Finding Tree

Yes

Selected band is working and calibrated.

re all 3 bands measured?

Yes

Rx chain is functional

and calibrated

Receiver Fault Finding Tree part 1

= To be done in all

three bands.

re all 3 bands measured?

Yes

Are all 3 bands defective?

Yes

Oscilloscope:

Check supply voltages of RF ASIC: VR4 = 2.8V ? (TP: VR4)

Yes

Oscilloscope:

Check supply voltages of RF ASIC: VR6 = 2.8V ? (TP:VR6)

Yes

Continue with single band fault finding.

Check supply filter components (C2233, C7519, C7520) and UEM

Check supply filter components (C2231, C7521) and UEM

Receiver Fault Finding Tree part 2

Receiver Fault Finding Tree part 3

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Oscilloscope:

Check reference voltages of RF part: VrefRF01 = 1.35V ? (TP: VrefRF01*)

Yes

Check supply filter components (R7511, C7524) and UEM

Receiver Fault Finding Tree part 4

Oscilloscope:

Check reference voltages of RF part: VrefRF02 = 1.35V ? (TPs: VrefRF02* and VrefRF02**)

Yes

Phoenix:

Phone: local mode

RF Controls

Active Unit: Rx Op. Mode: Rx/Tx channel: default (mid) AGC: 14

Continuous

Signal Generator:

To be tuned that input power at spectrum analyzer: –60dBm (power at probe:

Frequency: calculated from Phoenix offset: 67.71kHz

= approx. -63 dBm)

Pref

Spectrum Analyzer: 1)

Check Rx/Tx Switch (Diplexer)

Depending on selected band, check level at TPs:

850

GSM900 output Rx1 Pref -1.5dB ? GSM1800 output Rx2 Pref -2.0dB ? GSM1900 output Rx3 Pref -2.5dB

Yes

Check supply filter

components (R2900, R2901, C2900, C2901) and UEM

Receive Fault Finding Tree part 5

Change Z7800

Note 1): RF levels are dependent on RF probe and have to be validated with a known good sample.

Oscilloscope:

RX IQ levels ok (TPs: RXI, RXQ) ?

Yes

Oscilloscope:

RF-BB serial interface ok?

(TPs: RFBusData, RFBusClk, RFBusEna1)

Yes

Change RF ASIC (Helgo)

BB error: Check UPP

Change RF ASIC (Helgo)

Receiver Fault Finding Tree part 6

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Select faulty band in Phoenix and continue measurements on dedicated Rx part.

Phoenix:

SNR Measurement

open

Meas. Mode: Fast SNR

Measure

Press

Signal Generator:

Level: –92dBm

Frequency: calculated from Phoenix

Phoenix: SNR measurement ok?

(SNR > 18.37dB)?

Phoenix:

Phone: local mode

RF Controls

Active Unit: Rx Op. Mode: Rx/Tx channel: default (mid) AGC: 14

Continuous

Single band fault finding

Receiver Fault Finding Tree part 7

Yes

Front end is ok.

Phoenix:

Phone: local mode

RF Controls

Active Unit: Rx Op. Mode: Rx/Tx channel: default (mid) AGC: 10

Continuous

Signal Generator:

Level: –60dBm

Frequency: calculated from Phoenix offset: 67.71kHz

Continue with Rx Fault Finding part 6.

Receiver Fault Finding Tree part 8

Signal Generator:

To be tuned that input power at spectrum analyser: –60dBm power at probe:

Frequency: calculated from Phoenix offset: 67.71kHz

=approx. -63dBm)

Pref

Spectrum Analyzer: 1)

Center Freq: calculated from Phoenix

RBW 20kHz

Check Rx SAW filter and matching network of selected band:

GSM900 TPs: INM_G_RX / INP_G_RX

GSM850

both output levels > Pref -3.5dB ? GSM1800 TPs: INM_D_RX / INP_D_RX both output levels > Pref -6dB ?

Yes

Note 1): RF levels are dependent on RF probe and have to be validated with a known good sample.

Change Rx SAW filters (Z7802, Z7803) or component(s) of matching network depending on selected band

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