Ericsson a1018 Service Manual

Trouble Shooting Guide, Advanced

Trouble Shooting Guide, Advanced

by Toko ([e-mail])

4/00021-3/00021/16 C Approved according to 1776-3/FEA 209 544

Trouble Shooting Guide, Advanced

Contents

1 Explanations........................................................................................................................3

2 Enter Test Program............................................................................................................7

3 Calibration IQ...................................................................................................................12

4 TxVCO...............................................................................................................................14

5 VCXO.................................................................................................................................19

6 Calibration RSSI...............................................................................................................23

7 Power Level Calibration...................................................................................................25

8 Intermediate Power Calibration......................................................................................30

9 Transient Spectrum (Spectrum due to Switching).........................................................31

10 Modulation Spectrum Switched Mode (Spectrum due to Modulation)......................36

11 EE-prom ............................................................................................................................45

12 ADC Calibration (Voltage Calibration)..........................................................................46

13 Current Calibration..........................................................................................................49

14 Network Problems ............................................................................................................53

15 Phase and Frequency Error.............................................................................................62

16 Output Power....................................................................................................................63

17 Burst Timing (Power Time Template)............................................................................67

18 Sensitivity (Rx Quality) ....................................................................................................69

19 Rx Level.............................................................................................................................74

20 Audio..................................................................................................................................76

21 Keyboard...........................................................................................................................83

22 Display................................................................................................................................85

23 Buzzer ................................................................................................................................89

24 Illumination.......................................................................................................................90

25 Top Indicator.....................................................................................................................92

26 SIM Problems (“Insert card”).........................................................................................94

27 Selftest................................................................................................................................97

28 ADC Values.......................................................................................................................99

29 Revision History..............................................................................................................102

4/00021-3/00021/16 C 2(102)

1 Explanations

1.1 Conditions

All measurements described in this Trouble Shooting Guide – Advanced, are performed in
EFRA with test program in the phone. Some of the faults can occur in tests without test
program, e.g. Go/No Go -tests. In these cases you have to program the phone with test program
before starting to trouble shoot using this guide.

For trouble shooting with signal program, see 4/00021-2/FEA 209 544/16.
For component placing see1078-2/FEA 209 544/16.
In case of liquid damage no further action should be taken, handle the unit according to the local

company directives.
When measuring with the probe, remember to set the correct attenuation (ext. preamp. gain) on

the spectrum analyzer. To get the most appropriate value, set the gain according to Tx output on
a correct working card.

Trouble Shooting Guide, Advanced

1.2 Abbreviations

B: Crystal.
C: Capacitor.
D: Digital circuit.
F: Over voltage protection.
H: Buzzer, LED and pads for display.
J: Connector.
L: Coil.
N: Analogue circuit.
P: Test point.
R: Resistor.
S: Keyboard pads.
U: BALUN Component that converts a balanced signal to an unbalanced or the other way

around.
V: Transistor or diode.
X: Contact surface on the circuit board.
Z: Filter.

4/00021-3/00021/16 C 3(102)

Trouble Shooting Guide, Advanced

AGND: Ground for analogue signal.
AFMS: Audio from mobile station.
ATMS: Audio to mobile station.
DCIO: DC voltage through the system connector for charging.
GND: Ground.
LED3K: Logical signal that activates the background illumination.
ONSWAn: Voltage from the On/Off key that starts the phone.
RTC: Real Time Clock. The clock that keeps track of time and date.
SIMCLK: Signal from the processor used for communication to SIM, clock signal.
SIMDAT: Signal from the processor used for communication to SIM, data signal.
SIMRST: Signal from the processor used for communication to SIM, r eset signal.
SIMVCC: Feed voltage for SIM.
VBATT: Battery voltage (4.8V)
VCORE: DC voltage for the processor and memory (2.5 V)
VDIG: DC voltage for the processor and memory (3.2 V)
VLCD: DC voltage for the display that controls the contrast.
VRAD: DC voltage for the radio part except the synthesiser. (3.75 V)
VRTC: DC voltage for the real time clock. (2.5 V)
VVCO: DC voltage for the synthesiser (3.75 V)
I2C: Communications standard for two-way communication using only 2 wires,

clock and data.

4/00021-3/00021/16 C 4(102)

1.3 Pin placing

Trouble Shooting Guide, Advanced

4/00021-3/00021/16 C 5(102)

Trouble Shooting Guide, Advanced

4/00021-3/00021/16 C 6(102)

2 Enter Test Program

2.1 Introduction

To be able to use EFRA, the phone has to be programmed with test program. The programming
is also performed in EFRA.

If the phone cannot be programmed, proceed to section 2.3.
If the phone does not start in the radio calibration or trouble shooting part of EFRA, despite an

approved flash programming, proceed to section 2.2.

2.2 The phone does not start in the test program

Trouble Shooting Guide, Advanced

Attach a dummy battery and press the On/Off button. Check the display and the current
consumption.

If the phone starts (showing the revision of the test program in the display) and consumes 30 –
50 mA, the phone is usually without fault.

Check your equipment.
The following things are necessary for the phone to start in the test program:

Correct battery voltage (4.8 V).
Correct feed voltage to the trouble shooting box (15 V).
The current limitation must be set high enough on both outputs of the power amplifier (2A).
The phone must be started before clicking on the ”Startup” in EFRA.
The following signal must be found at the system connector of the phone: TTMS, TFMS,
VPPFLASH, GND and VDD.
Correct serial port of the trouble shooting box chosen.
”Mode”-switch should be in position ”Service”.
A Hardlock connected and installed.

If the fault really is electrical, open the phone and make a visual check of the board.
Make sure that there is not any liquid damage, burned or damaged pads at the system connector

or bad soldering of e.g. D600 or D610.
Power up the board and start it by using a pulse at the DCIO (or the On/Off button).
Check the amplitude of MCLK at C680 using the spectrum analyser (>3 dBm). We have been

using the following settings: CF – 13MHz, SPAN – 1 MHz, RBW – 10 kHz, VBW – 10 kHz
andSWEEP–30ms.
If MCLK is too low, the fault usually is due to L340, B301 or a s hort circuit in C343.

If the fault still remains, try to program the phone again.
If the phone consumes more then 200 mA, proceed to section 2.4.3.

If the phone consumes no current at all, when the button is pressed, open the phone and check
for liquid damage. Also make sure that the keyboard and the keyboard pads are okay and that
they are clean.

4/00021-3/00021/16 C 7(102)

If there is a signal program in the phone, you have to program it with the test program.

2.3 The phone cannot be programmed

Makesurethat:
the battery screws are okay and tightened;
the system connector is not dirty or liquid damaged.

Attach a dummy battery. If the phone consumes current immediately, the fault is usually due to
a short circuit of VBATT, but first you must make sure that the isolation of the frame is not in
contact with the plus pole of the board.

Trouble Shooting Guide, Advanced

Start the phone with the On/Off button and check the current consumption.
If the phone consumes no current at all when the button is pressed, there is probably liquid

damage. Open the phone and check for liquid damage. Also make sure that the keyboard and the
keyboard pads are okay and that they are clean.

If the phone consumes more then 200 mA, proceed to section 2.4.3.
If the phone does not start, try to program it on board level.

If the phone does not start in the flash programmer, proceed to section 2.4.1.
If the phone can be programmed, but does not start afterwards or is troublesome in the flash
programmer, proceed to section 2.4.2.
If the phone starts after programming, the fault is probably solved, but to eliminate the
possibility of intermittent faults make sure that the soldering at D600, D610 or D630 are correct.

4/00021-3/00021/16 C 8(102)

2.4 Measuring at a powered circuit board

2.4.1 Does not start in the flash programmer

Make sure that the pads of the system connector are not burned or in any way damaged.
Attach the board to the fixture. Power up the board by keeping DCIO high.
Measure the voltages VDIG (3.2 V) and VCORE (2.5 V).

If any of the voltages are too low, measure the resistance to ground (VDIG > 1 kohm, VCORE
> 25 kohms).
If the resistance is correct, replace the corresponding circuit (VDIG - N701, VCORE - N700).
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
increasing after removal. Do not forget to mount all the components that have been removed.
You should also replace the circuits on which you have lifted the pins. The short circuit is
usually due to D610, D600 or any of C600, C602-C611, C614, C800, C802-C807, C902, C906
for VDIG and D900 or any of C900, C901, C903-C905 for VCORE.

Trouble Shooting Guide, Advanced

If any of the voltages are too high, replace the corresponding circuit.

Measure the power reset at C710 (>3 V). If it is lower, the fault is probably due to C710 or
N550.

Measure the voltage VRAD/VVCO (3.8 V).

If the voltage is incorrect, measure the resistance between ground and N580:5 (50 kohms).

If the resistance is correct, replace N580.
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short-circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
raising after removal. Do not forget to mount all the components that have been removed. You
should also replace the circuits on which you have lifted the pins. The short circuit is usually
due to N550, or any of the 10nF-capacitors on VRAD/ VVCO.

Check the amplitude of the clock, using the oscilloscope, at B301:3 (>0.7 V t- t). You can also
use the spectrum analyser to check the amplitude (>1 dBm). We have been using the following
settings for the oscilloscope: CF – 13MHz, SPAN – 1 MHz, RBW – 10 kHz, VBW – 10 kHz
and SWEEP – 30 ms. A fault of the clock can be due to L340, B301 or a short circuit in C343,
D600, N300 or C300. Sometimes the fault is due to N202.

4/00021-3/00021/16 C 9(102)

Trouble Shooting Guide, Advanced

Make sure that the soldering at D600, D610 or D630 are correct. If they are correct and all the
feed voltages and the clock are correct, the fault is usually due to D600. The fault can also be
due to D610 or D630.

Try to program the phone between each replacement.

2.4.2 Can be programmed, but does not start afterwards or is
troublesome in the flash programmer

Make sure that the pads of the system connector are not burned or in any way damaged.
Open the phone and check for liquid damage.
Attach the board to the fixture. Power up the board by keeping DCIO high.

Measure the voltages VDIG (3.2 V) and VCORE (2.5 V).
If any of the voltages are too low, measure the resistance to ground (VDIG > 1 kohm, VCORE

> 25 kohms).
If the resistance is correct, replace the corresponding circuit (VDIG - N701, VCORE - N700).
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
raising after removal. Do not forget to mount all the components that have been removed. You
should also replace the circuits on which you have lifted the pins. The short circuit is usually
due to D610, D600 or any of C600, C602-C611, C614, C800, C802-C807, C902, C906 for
VDIG and D900 or any of C900, C901, C903-C905 for VCORE.

If any of the voltages are too high, replace the corresponding circuit.

Measure the voltage VRAD/VVCO (3.8 V).

If the voltage is incorrect, measure the resistance between ground and N580:5 (50 kohms).
If the resistance is correct, replace N580.
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
raising after removal. Do not forget to mount all the components that have been removed. You
should also replace the circuits on which you have lifted the pins. The short circuit is usually
due to N550, or any of the 10nF-capacitors on VRAD/ VVCO.

Check the amplitude of the clock, using the oscilloscope, at B301:3 (>0.7 V t- t). You can also
use the spectrum analyser to check the amplitude (>1 dBm). We have been using the following
settings for the oscilloscope: CF – 13MHz, SPAN – 1 MHz, RBW – 10 kHz, VBW – 10 kHz
and SWEEP – 30 ms. A fault of the clock can be due to L340, B301 or a short circuit in C343,
D600, N300 or C300. Sometimes the fault is due to N202.

4/00021-3/00021/16 C 10(102)

Make sure that the soldering at D600, D610 or D630 are correct. If they are correct and all the
feed voltages and the clock are correct, the fault is usually due to D600. The fault can also be
due to D610 or D630.

Try to program the phone between each replacement.

2.4.3 Consumes more then 200 mA

Open the phone and check for liquid damage.
Make sure that the pads of the system connector are not burned.
Attach the board to the fixture. Power up the board by keeping DCIO high.

Measure the voltages VDIG (3.2 V) and VCORE (2.5 V).

Trouble Shooting Guide, Advanced

If any of the voltages are too low, measure the resistance to ground (VDIG >1 kohm, VCORE
>25 kohms).
If the resistance is correct, replace the corresponding circuit (VDIG - N701, VCORE - N700).
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
raising after removal. Do not forget to mount all the components that have been removed. You
should also replace the circuits on which you have lifted the pins. The short circuit is usually
due to D610, D600 or any of C600, C602-C611, C614, C800, C802-C807, C902, C906 for
VDIG and D900 or any of C900, C901, C903-C905 for VCORE.

If any of the voltages are too high, replace the corresponding circuit.

Measure the voltage VRAD/VVCO (3.8 V).
If the voltage is incorrect, measure the resistance between ground and N580:5 (50 kohms).

If the resistance is correct, replace N580.
If the resistance is too low, use the schematics. Remove the components one by one (or lift the
pin/pins feeding the circuit), that is fed from the short circuited voltage, and measure the
resistance after each removal. You have found the faulty component when the resistance is
raising after removal. Do not forget to mount all the components that have been removed. You
should also replace the circuits on which you have lifted the pins. The short circuit is usually
due to N550, or any of the 10nF-capacitors on VRAD/ VVCO.

Check the amplitude of the clock, using the oscilloscope, at B301:3 (>0.7 V t- t). You can also
use the spectrum analyser to check the amplitude (>1 dBm). We have been using the following
settings for the oscilloscope: CF – 13MHz, SPAN – 1 MHz, RBW – 10 kHz, VBW – 10 kHz
and SWEEP – 30 ms. A fault of the clock can be due to L340, B301 or a short circuit in C343,
D600, N300 or C300. Sometimes the fault is due to N202.

Make sure that the soldering at D600, D610 or D630 are correct. If they are correct and all the
feed voltages and the clock are correct, the fault is usually due to D600. The fault can also be
due to D610 or D630.

Try to program the phone between each replacement.

4/00021-3/00021/16 C 11(102)

3 Calibration IQ

3.1 What is calibration IQ

The IQ-filter consists of two parts. The first part is a passive lowpass-filter between the
waveform generator in D600 and N202 consisting of R642-R645, C106 and C108. The second
part is a software- controlled filter in N202 that is calibrated with a certain test signal from the
waveform generator.

When calibrating, the transmitter is powered up in static mode with the test modulation. The
peak, that exists at CF-201 kHz related to the highest peak (CF+67 kHz), is measured, and the
LPBW/LPQ parameters in Homeros are tuned, until correct suppression (typ -21 dBm) is
obtained.

Trouble Shooting Guide, Advanced

Fig. 3.1

3.2 How to find the fault

Open the phone and check for liquid damage.
Attach the board in the fixture and start the test program.

NOTE! If the card i s of type 2, with the EKA power module, remember to attach the

negative bias voltage in the fixture.

Change the settings on the spectrum analyser to: SPAN: 1 MHz, RBW: 10 kHz, VBW:10 kHz,
SWEEP: 30 ms.

Start the transmitter in static mode with modulation on the middle channel (699) on the DCS
1800-band (Fig. 3.2). If the transmitter does not lock, decrease the sweep current.

4/00021-3/00021/16 C 12(102)

Trouble Shooting Guide, Advanced

Fig. 3.2

Make sure that the spectrum looks like in Fig. 3.1.
If the spectrum does not look like the figure it is either one of the modulation signals (MODQN,

MODQP, MODIN, MODIP) that is missing from D600 or the lowpass-filter to the modulation
signals that is faulty (R642-R645, C106, C108).

Measure on the capacitors with an oscilloscope. The signals are sinus shaped with the frequency

67.7 kHz and the amplitude 3.0 V. Compare the signals with each other. The fault is probably
on the one modulation signal that differ from the others. If the modulation signals looks good
and are in the right phase (90 degrades turned compared to each other) then the fault could be
caused by N202.

4/00021-3/00021/16 C 13(102)

4TxVCO

4.1 What is TxVCO – Calibration

In the GSM900-system a phone can communicate with the base station at 124 frequencies in
each direction (890.2 - 914.8 MHz for the transmitter and 935.2 - 959.8 MHz for the receiver).
In the GSM1800-system it is possible to communicate at 374 frequencies in each direction
(1710.2 – 1784.8 MHz for the transmitter and 1805.2 – 1879.8 MHz for the receiver).

The communication between the base station and the phone are done switched. The system
makes it possible to change frequency between each burst. For every new burst the transmitter
synth of the phone has to lock again at the frequency the base station expects, before activating
the transmitter.

Fig 4.1 and Fig 4.2 shows two simplified diagrams over the lock-on of the Tx-synth. The
frequencies are for channel 62 (GSM900) and channel 699(GSM1800).

Trouble Shooting Guide, Advanced

GSM 900

Fig. 4.1

4/00021-3/00021/16 C 14(102)

GSM 1800

Trouble Shooting Guide, Advanced

Fig. 4.2

The frequency of the transmitter has to lock during a predestinated time. To make the locking
time fast enough, the phone uses pre-learned TxVCO-values read from the EEPROM. The l ock­on begins with the TxVCO-AC transforming a, for this particular channel, saved EEPROM­value to a start value for the control voltage of the VCO (N390). The voltage is a little bit higher
than the expected value when the synth has locked on. By using the start value of the control
voltage the VCO generates a transmitter frequency that is only a little too high. The transmitter
frequency is fed back through a mixer to the Phase detector (both inside N202). The Phase
detector compares the mixed frequency (91 or 52 MHz) with an intern reference signal (7x13
=91 or 4x13 =52 MHz). The result of the phase comparison is a DC voltage that controls the
VCO. The TxVCO-DAC is disconnected and the Phase detector takes over the adjustment of the
control voltage to the VCO. When the transmitter synth has locked on (the Phase detector in
N202 has stabilized the control voltage and the frequency), the phone can begin to transmit.

The start value of the synth, the TxVCO value, has to be calibrated due to the differences of
tolerance in the components of the transmitter synth. The calibration i s performed in switched
mode, at two channels: for GSM900 high (channel 94 or 908,8 MHz) and low (channel 30 or
896 MHz) and for GSM1800 high (channel 826 or 1773.0 MHz) and low (channel 570 or

1721.8 MHz). The values for other channels you get by interpolation.

The tables below (Table 4.1 and 4.2) show the limits for the T xV CO – values.

4/00021-3/00021/16 C 15(102)

GSM 900

TxVCO Min Max

Ch 30 56 A6 Hex

86 166 Dec

CH 94 6A BA Hex

106 186 Dec

Table 4.1

GSM 1800

TxVCO Min Max

Ch 570 37 87 Hex

55 135 Dec

CH 826 7E CE Hex

126 206 Dec

Table 4.2

Trouble Shooting Guide, Advanced

4.2 How to find the fault

Open the phone and check for liquid damage.
Power up the board and start the phone in the test program.
Measure the voltage at C853 and C854. Replace the corresponding capacitor if the voltage is

lower than approximately 1.1 V.

NOTE! If the card is of type 2 (roa 117 3258/2 or roa 117 3920/2), remember to attach the

negative bias voltage before changing to static mode.

GSM900:

Start the transmitter in static mode at channel 62 (902.4 MHz) and check the amplitude and the
frequency. If the frequency i s faulty, try to decrease the ”Adjust sweep current” until the
frequency of the transmitter has locked on. We have been using the following settings on the
spectrum analyser while measuring: CF- 902.4 MHz, SPAN- 200 MHz, RBW- 10 kHz, V BW­10 kHz and Sweep- 30 ms.

If the transmitter locks, start the transmitter in switch mode at middle channel (62) with ”DAC 4
value” at FF. We have been using the following settings on the spectrum analyser while
measuring: CF- 902.4 MHz, SPAN- 0 MHz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8
ms.

Check if there is an output power (32 dBm) at the antenna plate using the spectrum analyser.
If the output power is correct, the phone is probably without fault. Try the phone in the test
again.
If there is no switched output power at all or if it i s too low, proceed to chapter 14 (”Network
problem”) section 14.3.1.

If the transmitter does not lock, start the transmitter in static mode again and change the settings
for the spectrum analyser to: 954.4 MHz, SPAN- 200 MHz, RBW- 10 kHz, VBW- 10 kHz and
Sweep- 30ms.

Check the frequency and the amplitude of the LO-signal at N331:1 (0dBm).

4/00021-3/00021/16 C 16(102)

Trouble Shooting Guide, Advanced

If the amplitude and the frequency is correct, proceed to section 14.2.1.
If the frequency is correct, but the amplitude is too low, check the feed voltage at N331:7 (3.7
V).

If the voltage is correct, replace N331.
If the voltage is incorrect, check VVCO (3.8 V), SYNTON (3.8 V), BANDSEL and V337 with
the belonging components.

If the amplitude is correct, but the frequency is incorrect, the fault is usually due to N300. It can
also be due to N331 or D600.

If the signal is several MHz wide, replace C313.

(To make a more accurate frequency measuring, try to decrease SPAN to 1 MHz.)

GSM1800:

Start the transmitter in static mode at channel 699 (1747.4 MHz) and check the amplitude and
the frequency. If the frequency is faulty, try to decrease the ”Adj ust sweep current” until the
frequency of the transmitter has locked on. We have been using the following settings on the
spectrum analyser while measuring: CF- 1747.4 MHz, SPAN- 200 MHz, RBW- 10 kHz, V BW­10 kHz and Sweep- 30 ms.

If the transmitter locks, start the transmitter in switch mode at middle channel (699) with ”DAC
4 value” at FF. We have been using the following settings on the spectrum analyser while
measuring: CF- 1747.4 MHz, SPAN- 0 MHz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8
ms.

Check if there is an output power (28-32 dBm) at the antenna plate using the spectrum analyser.
If the output power is correct, the phone is probably without fault. Try the phone in the test
again.

If there is no switched output power at all or if it i s too low, proceed to chapter 14 (”Network
problem”) section 14.3.1.

If the transmitter does not lock on, start the transmitter in static mode again and change the
settings for the spectrum analyser to: 1838.6 MHz, SPAN- 200 MHz, RBW- 10 kHz, VBW- 10
kHz and Sweep- 30ms.

Check the frequency and the amplitude of the LO-signal at N330:1 (0dBm).
If the amplitude and the frequency are correct, proceed to section 14.2.2.

If the frequency is correct, but the amplitude is too low, check the feed voltage at N330:7 (3.7
V).

If the voltage is correct, replace N330.
If the voltage is incorrect, check VVCO (3.8 V), SYNTON (3.8 V), BANDSEL and V338 with
the belonging components.

If the amplitude is correct, but the frequency is incorrect, the fault is usually due to N300. It can
also be due to N330 or D600.

If the signal is several MHz wide, replace C313.
(To make a more accurate frequency when measuring, try to decrease SPAN to 1 MHz.)

4/00021-3/00021/16 C 17(102)

4.2.1 Tx–synth fault for GSM900

Power up the board and enter the test program.
Start the transmitter in static mode at channel 62.

Use the following settings for the spectrum analyser: CF- 902.4 MHz, SPAN- 200 MHz, RBW­10 kHz, VBW- 10 kHz and Sweep- 30 ms.

Measure the amplitude and the frequency of the signals TXINA and TXINB at C370 and C371
( -13 dBm, the frequency should be 902.4 MHz when the synth has locked).Measure on both
sides of the capasitors to make sure that they are not broken.
If the TXIN-signal is too low, the fault is usually due to N390 (9 dBm at N390:6) or its feed
voltages. The fault can also be due to too large attenuation in N391, C370 or C371.
If the level of the TXIN-signal is correct, find out if the LO signal (954.4 MHz) is correct.
Measure at L331 (-7 dBm).

If the LO signal is correct the fault is probably due to N202, see chapter 18.5.
If it is low or missing, follow the signal back to the VCO (N331:1).

Trouble Shooting Guide, Advanced

If the signal is low or missing at the VCO, check that the feed voltage, VV CO on N331:7, is
correct (3.8 V). Also check the control voltage on N331:5 (2.0 V).
If the control voltage is incorrect, the fault is probably due to N300 or C300.
If the voltages are correct, N331 is probably broken.

4.2.2 Tx–synth fault for GSM1800

Power up the board and enter the test program.
Start the transmitter in static mode at channel 699.

Use the following settings for the spectrum analyser: CF- 1747.6 MHz, SPAN- 200 MHz,
RBW-10kHz,VBW-10kHzandSweep-30ms.

Measure the amplitude and the frequency of the signals TXINA and TXINB at C370 and C371
( -10 dBm, the frequency should be 1747.6 MHz when the synth has locked). Measure on both
sides of the capasitors to make sure that they are not broken.
If the TXIN-signal is too low, the fault is usually due to N390 (11dBm a t N390:6) or its feed
voltages. The fault can also be due to too large attenuation in N391, C370 or C371.
If the level of the TXIN-signal is correct, find out if the LO signal (1838.6 MHz) is correct.

Measure at N202:40,41.
If the LO signal is correct the fault is probably due to N202, see chapter 18.5.
If it is low or missing, follow the signal back to the VCO (N330:1).

If the signal is low or missing at the VCO, check that the feed voltage, VV CO on N330:7, is
correct (3.8 V). Also check the control voltage on N330:5 (2.0 V).
If the control voltage is incorrect, the fault is probably due to N300 or C300.
If the voltages are correct, N330 is probably broken.

All values are approximates, measure the exact values for your equipment using an approved
phone.

4/00021-3/00021/16 C 18(102)

5VCXO

5.1 What is VCXO

The phone has got a reference crystal of 13 MHz, which signal is used for both the radio and the
logic.

The logic uses the clock signal MCLK as master clock and for the synchronisation of the digital
circuits of the logic.

The radio uses the 13 MHz signal as a reference signal for frequency regulation of both the
transmitter and the receiver.

The frequency fault of both the transmitter and the receiver must be inside the valid limits. The
phone has to have the possibility to control the frequency of the reference crystal to be able to
maintain the limits during different circumstances. This is possible since the reference crystal is
a Voltage Controlled Crystal Oscillator (VCXO). The schematic is shown in the figure below.

Trouble Shooting Guide, Advanced

Fig. 5.1

The crystal B301, the capacitors C321, C322, C323 and the varicap diode V302 are forming an
oscillating circuit. The active part of the oscillating circuit is in N202. By changing the DC
voltage of the varicap diode its capacitance changes, this changes the frequency of the
oscillating circuit. The control voltage VCXOCONT for the varicap diode comes from a DAC
in N800. The range of the DAC is between 0 and 3FF Hex, that is equivalent to a control
voltage between 0 and 3 V.

The frequency of the oscillating circuit is amplified in N202 and goes to the radio and the logic
through two outputs called 13MHz and MCLK.

5.2 VCXO measurements in the radio calibration in EFRA

There are three measurements and one calibration, concerning VCXO, in the radio calibration in
EFRA. The measurements are:

1. VCXO Control at DAC 00 Hex;

2. VCXO Control at DAC 3FF Hex;

3. VCXO Control Range.

4/00021-3/00021/16 C 19(102)

Trouble Shooting Guide, Advanced

These three measurements control the adjustment range, in ppm, of the crystal. The
measurement is performed as follow:

The transmitter is started in static mode at any channel and the VCXO value 00 Hex.
The output frequency of the transmitter is measured.
The adjustment range in ppm for DAC 00 Hex is measured according to the formula below:

The adjustment range (in ppm) = (The measured frequency – the frequency of the channel) *
1000000 / the frequency of the channel

E.g. channel 699:
The frequency of the channel: 1747.6 MHz
The measured frequency: 1747.4 MHz
(1747.4 – 1747.6) * 1000000 / 1747.6 = - 114 ppm

The abbreviation ppm means ”parts per million”, i.e. 1 Hz divergence per MHz of the output
frequency of the transmitter. Meaning that a difference of one ppm at the middle channel of the
transmitter (1747.6 MHz) gives a frequency divergence of 1747.6 Hz.

The VCXO value changes to 3FF and the frequency of the transmitter is measured again. The
adjustment range is calculated in the same way, but the result should be positive.

The VCXO Control Range is calculated from the values from the two measurements above. You
check the adjustment range for the values between 00 and 3FF Hex.

The measuring of the adjustment range is important to verify that the reference frequency can be
controlled enough, up and down.

In Calibration VCXO, the 13 MHz crystal is being trimmed at channel 570. By sending the
DAC value 200 Hex and comparing the received frequency to the one for channel 570, an offset
is calculated. This offset is used in an algorithm to establish the value for the DAC for the
TCXO.

The calibrated VCXO value is somewhere in the middle of 00 and 3FF, Hex.

4/00021-3/00021/16 C 20(102)

Table 5.1shows the limits for the VCXO measurements.

Parameter Min Max Unit

VCXO

Control at

DAC 00 Hex

VCXO

Control at

DAC 3FF Hex 13 67 ppm

VCXO

Control Range 40 80 ppm

Calibrated

VCXO 262 762 Dec

DAC 106 2FA Hex

-67 -13 ppm

Table 5.1

Trouble Shooting Guide, Advanced

5.3 How to find the fault

Open the phone and check for liquid damage.
Start the phone in the test program.
Start the transmitter in static mode at middle channel (699). Make sure that the transmitter locks.
Turn off t he modulation by selecting ”Mod off”.
Go to Misc /DAC Parameter.
Set TCXO to 00 Hex. Notice t hat the DAC value does not change until clicking at ”Close”.

Measure the DC voltage at C320 (0.3 V).

Set TCXO to 3FF Hex. Notice that the DAC value does not change until clicking at ”Close”.
Measure the DC voltage at C320 (2.9V).

If both voltages are correct, but any of the VCXO measurements are incorrect, the fault is
usually due to B301. Sometimes the fault is due to V302, C321, C322 or C323.
If both voltages are constantly too low, remove C320. Measure the voltages again.

If the voltages are correct now, the fault was a short circuit in the capacitor.
If the fault remains, it is usually due to N800,C853 or C854. (The voltage at C853 and C854
should be 1.1V)

If both voltages are equal, but not 0 V, the fault is almost always due to N800.
If both voltages are correct, but the V CXO calibration is incorrect, the fault i s usually due to

B301 or V302. Sometimes it is due to C321, C322 or C323.

VCXO faults can be due to N202, but that is not very common.

4/00021-3/00021/16 C 21(102)

Trouble Shooting Guide, Advanced

You can verify that the fault is gone by measuring the output frequency of the transmitter with
VCXO-DAC at 00 and 3FF Hex and compare the result with table 5.2.

Parameter Min Max Unit

VCXO

Control at

DAC 00 Hex 1747.4829 1747.5773 MHz

VCXO

Control at

DAC 3FF Hex 1747.6227 1747.7171 MHz

Table 5.2 (Applies for channel 699)

4/00021-3/00021/16 C 22(102)

6 Calibration RSSI

6.1 What is RSSI

In the mobile phone, the received RF-signal strength is measured and indicated by a f unction
called RSSI, Received Signal Strength Indicator.

During a call in progress the phone measures the current signal strength sequentially from a
number of base stations ordered by the switch when setting up t he call. The measurement starts
at the base station serving cell and continues with the RF-signals of up to 6 surrounding base
stations. The measurement cycle is continually repeated.

The logic part of the phone then calculates a number of values of the received RF-signals and
reports the amplitude of the RF-signals from the different base station to the switch through a
logical channel.

The signal strength report is used in an evaluation process for Location and Handover, i.e. when
the switch evaluates the speech quality, signal strength and traffic parameters to be outside the
limit values of the current physical channel and chooses to start a new channel for the
connection. A physical channel is the combination of a timeslot (TS) and a radio channel
(ARFCN). The physical channel (TS/ARFCN) can be allocated to the current base station or any
of the surrounding base stations at handover.

Trouble Shooting Guide, Advanced

For the speech quality and the MS to Base distance, it is important that the reported
measurements of the RF-signal are correct and calibrated towards known values. If the reported
values are too high it results in late handovers and bad readability due to the limits that are set
out of reach for the MS. The opposite, t oo low values, provokes the switch to make unnecessary
handovers, increased traffic load and perhaps dropped calls by forced release.

The received signal carries information both in phase as well as amplitude. The phase contains
the digital information (speech and signalling data) and is detected in a phase digitizer for
further processing in the main program. The amplitude of the received signal is measured in
N800, giving a value called RSSI.

RSSI is used for two measurement functions, electrical and numerical (mean value and
momentary value). The electrical value of the RSSI is used to report the signal strength to the
switch through the base station as current Rx-level. The numerical RSSI-value is calculated and
only used internally in the phone by the DSP.

The RSSI measuring procedure is to compare the strength of the measured signals and compare
them to a calibrated scale of reference levels and point out the one closest to the current RF­level. There are two scales, one for GSM900 and one for GSM1800, both are calibrated
separately. To create these scales, the MS is calibrated with known RF-signal levels from –
110dBm to –40dBm, with a 5dBm increment at a frequency in the Mid ARFCN range (ARFCN
62 is usually used as a mid channel for GSM900 and ARFCN 699 for GSM1800). This
procedure is called RSSI calibration.

These 15 RF-signal levels are digitized by the RSSI function and temporarily saved in the RAM
memory by a test program. The test program then performs an interpolation and calculates the
rest of the (up to 256) reference value positions and loads them into a part of the MS program
memory, EEPROM.

4/00021-3/00021/16 C 23(102)

Every RF-signal level, that is processed by the RSSI-function, can now be presented in digital
form by reading the nearest corresponding reference level from the EE-PROM, with a resolution
of 16 bits, and sending it as current Rx-level information to the base station.

These reference l evels are unique for every phone since the signal path through every receiver is
dependent on unique parameter values. As, for instance, component tolerances, mounting,
soldering and so on. Every change, for instance a repair, an adjustment, a component being
soldered, a component ageing and so on, brings the possible need of a new calibration.

6.2 How to find the fault

The fault can be due to either an incorrect measurement of the RSSI value or too large losses in
the signal path. If the RSSI calibration is incorrect for only one frequency band, GSM900 or
GSM1800, the fault is usually in the signal path, see chapter 18 (Sensitivity and Rx-quality) for
a hint on where to troubleshoot. To check the measurement of the RSSI value, only one of the
frequency bands is needed. We have used the GSM900 band.

Trouble Shooting Guide, Advanced

Set Rx-amplitude from GSM-test set to 947.4 MHz and -50 dBm. Use a modulated signal
(GMSK on).

Open the phone and check for liquid damage.
Attach the board to the fixture and start the test program.
Go to Radio/RSSI Measurement and make a RSSI measurement at channel 62.

If the RSSI value is about 0xC8, it is probably okay. But to be sure, measure at -100 dBm
(should be about 0x44).

If the RSSI value is 0x00 or 0xFF (for different signal strengths), the fault is usually due to
N800 or D600.
If the value is faulty, the problem is probably in N202, N800 or N300.

4/00021-3/00021/16 C 24(102)

7 Power Level Calibration

7.1 Introduction

In the GSM 900 system, it is possible for a phone to transmit with 15 different power levels,
from 33 dBm (power level 5) to 5 dBm (power level 19). In the GSM1800 system, it is possible
for a phone to transmit with 16 different power levels, from 30 dBm (power level 0) to 0 dBm
(power level 15). It is best to transmit at as low output power as possible, but with maintained
transfer quality, in order to e.g. save current in the battery and restrict the disturbances. The base
station evaluates the transfer quality and informs the phone when to change the output power.
For the base station to be able to regulate the output power of the phone in a satisfying way, the
power levels of the phone have to be as the base station expect. This means that the power levels
of the phone have to be calibrated to be accurate enough.

Trouble Shooting Guide, Advanced

Fig 7.1 shows a very simplified schematic of the power regulation.

Fig. 7.1

The calibrated DAC values are stored in the EEPROM. When the base station orders the phone
to transmit at a certain power level, the DAC value for the current power level is taken from the
EEPROM and sent to the Power level-DAC in N800. The output voltage POWLEV of the DAC,
lets the power regulation of the radio know how large the power should be. N550 uses
POWLEV to create the control voltage VREG with Offset level and Full Power level.It
regulates the amplification of the power amplifier. The regulation is fed back by measuring the
current consumption of the power amplifier using R412. The signal is called VSENSE.

Table 7.1 (GSM900) and 7.2 (GSM1800) shows the allowed DAC values and the output power
goal of the calibration.

4/00021-3/00021/16 C 25(102)

Trouble Shooting Guide, Advanced

Power

Level

Output

Power

(dBm)

5 32.5 ±0.3
6 30.5 ±0.3
7 29 ±0.5
8 27 ±0.5

9 25 ±0.5
10 23 ±0.5
11 21 ±0.7
12 19 ±0.7
13 17 ±0.7
14 15 ±0.5
15 13 ±0.5
16 11 ±0.5
17 9 ±0.5
18 7 ±0.5
19 5 ±0.5

Table 7.1 (GSM 900)

Power

Level

Output

Power

(dBm)

0 30 ±0.3

1 28 ±0.5

2 26 ±0.5

3 24 ±0.5

4 22 ±0.5

5 20 ±0.7

6 18 ±0.7

7 16 ±0.7

8 14 ±0.7

9 12 ±0.7
10 10 ±0.7
11 8 ±0.7
12 6 ±0.7
13 4 ±0.7
14 2 ±0.7
15 0 ±0.7

Table 7.2 (GSM1800)

4/00021-3/00021/16 C 26(102)

The power calibration is a part of the radio calibration in EFRA. The calibration is performed in
15 steps, from the highest (5) to the lowest (19), for GSM900 and in 16 steps for GSM1800 (0-

15), one step for each power level. The computer controls the calibration by setting t he Power
level DAC for the phone at the current power level and checking the output power using a
spectrum analyser or a GSM test set. Default values are used as starting DAC values. The
computer changes the DAC value to attain the correct output power for the current power level.
The value is temporarily saved in the RAM of the phone. When the computer has attained the
right output power for each power level, the values for the power levels not in use are first
interpolated, then all DAC values are saved in the EEPROM. If the correct power is not
achieved or one of the DAC values is outside of the limits, then the calibration has failed and
nothing is written i n the EEPROM.

7.2 How to find the fault

If the power calibration failed or if the output power is several dBm too low, open the phone and
check for liquid damage.
Make sure that the antenna connector (W101) is okay.
Power up the board and start it in the test program.

Trouble Shooting Guide, Advanced

Measure the voltage at C833. If it is lower than approximately 1.5 V, replace the capacitor.

For GSM900:

Start the transmitter in switch mode at middle channel (62) and ”DAC 4 value” at FF. Check if
there is enough output power (30- 35 dBm) at the antenna plate using the spectrum analyser. We
have been using the following settings while measuring: CF- 902.4MHz, SPAN- 0 Hz, RBW­300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.

If the output power is correct, the fault can be due to the frame. The fault can also be due to a
change in the characteristics in some of the components, participating in the power regulation,
because of ageing. For some power levels this can make the output power or the DAC values
ending up outside the limits. In that case, the fault is usually due to N400 or N550. The fault can
also be due to N800, N390 or D600.

If the output power is too low, measure the control voltage POWLEV at N550:10 using an
oscilloscope. It should l ook like in Fig 7.2.

Fig. 7.2

4/00021-3/00021/16 C 27(102)

Trouble Shooting Guide, Advanced

If the control voltage is too low, the fault is usually due to N800. It can also be due to D600.
If the control voltage is correct, measure VREG at N550:16 or N400:4 (type 2 PA 3.5 V, same
frequency), N400:7(Type 1 PA).

If VREG is too low, the fault is probably due to N550 or N400.
If VREG is correct, measure the signal Tx at N390:6 (10 dBm).

If the signal Tx is correct at N390:6, check the output power from N400:16 (Type 2 PA28
dBm), N400:4 (Type 1 PA 31 dBm).

If the output power is too low, replace N400.
If the output power is correct at N400 but low or missing at the antenna connector, the fault is
probably due to N203.

If the signal Tx is too low at N390:6, measure the feed voltage at N390:3 using an oscilloscope
(3.8 V, 215 Hz).

If the feed voltage is correct, the fault is usually due to N390 or N400.
If the feed voltage is incorrect, the fault is usually due to V350 or V351. Make sure that VRAD
is okay.

For GSM1800:

Start the transmitter in switch mode at middle channel (699) and ”DAC 4 value” at FF. Check if
there is enough output power (28- 32 dBm) at the antenna plate using the spectrum analyser. We
have been using the following settings while measuring: CF- 1747.6MHz, SPAN- 0 Hz, RBW­300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.

If the output power is correct, the fault can be due to the frame. The fault can also be due to a
change in the characteristics in some of the components, participating in the power regulation,
because of ageing. For some power levels this can make the output power or the DAC values
ending up outside the limits. In that case, the fault is usually due to N400 or N550. The fault can
also be due to N800, N390 or D600.

If the output power is too low, measure the control voltage POWLEV at N550:10 using an
oscilloscope. It should l ook like in Fig 7.2.

If the control voltage is too low, the fault is usually due to N800. It can also be due to D600.
If the control voltage is correct, measure VREG at N550:16 or N400:4 (type 2 PA 3.5 V, same
frequency), N400:7(Type 1 PA).

If VREG is too low, the fault is probably due to N550 or N400.
If VREG is correct, measure the signal Tx at N390:6 (13 dBm).

If the signal Tx is correct at N390:6, check the output power from N400:26(Type 2 PA31 dBm),
C408 (Type 1 PA 28 dBm).

If the output power is too low, replace N400.
If the output power is correct at N400 but low or missing at the antenna connector, the fault is
probably due to N203.

If the signal Tx is too low at N390:6, measure the feed voltage at N390:3 using an oscilloscope
(3.8 V, 215 Hz).

4/00021-3/00021/16 C 28(102)

Trouble Shooting Guide, Advanced

If the feed voltage is correct, the fault is usually due to N390 or N400.
If the feed voltage is incorrect, the fault is usually due to V350 or V351. Make sure that VRAD
is okay.

All the mentioned signal strength levels are approximate, especially when measuring at the
signal before the power amplifier, since the output power of the power amplifier radiates back
to the probe. You have to consider this when comparing your values with a reference.

4/00021-3/00021/16 C 29(102)

8 Intermediate Power Calibration

8.1 What is intermediate power

Intermediate Power is a calibration necessary to do to fulfil the demands of the GSM­specification for the up- and down-ramping of the power and to minimize the transient spectra.

The up- and down-ramping of the control voltage of the power amplifier does not change
momentarily from zero-to-max/max-to-zero. That would cause a large number of over tones due
to the switch. The up- and down-ramping of the control voltage are i nstead performed with two
help steps. The control voltage then passes through an exponential amplifier and a Bessel low
pass filter in N550 where the transient disturbance is reduced. This gives a control voltage
without the straight, vertical edges and the sharp corners that produces the over tones. The two
help steps in the up- and down-ramping of the power are called Intermediate Power level.

Trouble Shooting Guide, Advanced

The figure below shows the up-ramping of the control voltage before it passes through the
exponential amplifier and the low pass filter, i.e. what the up-ramping steps looks like.

Fig. 8.1

The three power steps Low Intermediate Power level, High Intermediate Power level and Full
Power level are set by the power level DAC in N800 and are amplified and filtrated in N550.

Low and High Intermediate Power level uses default values to generate the voltage.
Fullpowerlevel(5–19forGSM900and0–15forGSM1800) is calibrated so that the Power

levels are correct according to the GSM – specification.

Intermediate Power level is calculated at the power calibration and is not shown in the test
protocol.

4/00021-3/00021/16 C 30(102)