Ericsson PF 768 Guida

Approved according to 2/FEA 209 544

Trouble-shooting

instruction

PF 768

Service Manual by Toko

4/00021-2/FEA 209 544/11.C

PF768, Standard Electrical Repairs

4/00021-2/FEA 209 544/11.C 2(68)

Table of contents

1 Conditions .......................................................................................... 3

1.1 Component classes. ......................................................................... 3

1.2 Abbreviations. ................................................................................. 4

1.3 Pin placements ................................................................................ 6

2 No serv/not able to connect calls. ..................................................... 8

3 Doesn’t start. ................................................................................... 11

4 Audio. ............................................................................................... 21

5 Display. ............................................................................................ 29

6 SIM (“Insert card”). ....................................................................... 33

7 Keyboard ......................................................................................... 37

8 Illumination and buzzer. ................................................................ 42

9 RTC .................................................................................................. 50

10 Component lists ............................................................................... 52

10.1 Explanations .................................................................................. 52

10.2 Component list 2/ROA 117 3235/2 ............................................. 53

10.3 Mounting drawing table .............................................................. 67

10.4 Revision change table ................................................................... 67

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1 Conditions

1.1 Component classes.

All the components in the phone are divided into classes and after every component

in the troubleshooting guide you have a class written. The components are divided

into four classes: A, B, C and D.The class of the component depends on how much

of the phone’s performance is affected when replacing it.

Class A and B:A test call towards the “real” net (not only towards a GSM test

instrument) and run it through the normal tests is enough to verify the

functionality since the performance of the phone is only slightly

affected.

Class C: Since the tolerances of the component are so great it can substantially

affect the performance of the phone you need to calibrate it at station

level after replacing the component.

Class D: Class D components need to be calibrated at board level using very

advanced equipment and may therefore not be replaced.

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1.2 Abbreviations.

A: The power module at some phones.

B: Crystal.

C: Capacitor.

D: Digital circuit.

F: Over voltage protection.

G: VCO.

H: Buzzer, LED, pads for display.

J: Connector.

L: Coil.

N: Analogue circuit.

R: Resistor.

S: Keyboard pads.

U: BALUN. A circuit that converts a signal from balanced to unbalanced or the

opposite.

V: Transistor or diode.

X: Contact surface at the circuit board.

Z: Filter.

AGND: Ground for analogue signals.

DCIO: DC voltage used for charging the battery through the system connector.

DCON: Logical signal from the processor that keeps the phone running after

you’ve released the On/Off key.

EXTAUD: Input signal at the system connector that the processor uses to deter-

mine if there’s any external audio equipment attached.

EXTAUDI: The same signal as the EXTAUD signal but at the processor side.

GND: Ground.

LED3K: Logical signal used to activate the background illumination.

ONSRQ: Voltage from the On/Off key that starts the phone.

PORTHF: Input signal at the system connector that the processor uses to deter-

mine if there’s any handsfree equipment attached.

PHF1: The same signal as PORTHF but at the processor side.

REGON: Logical signal that activates the voltage regulators.

RTC: Real time clock. The clock that keeps track of time and date.

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SIMCLK: Clock signal from the processor used for communications with the

SIM.

SIMDAT: Data signal from the processor used for communications with the SIM.

SIMRST: Reset signal from the processor used for communications with the

SIM.

SIMVCC: Feed voltage for the SIM.

SWDC: Switched VBATT.

VANA: DC voltage for the analogue part of the logic (N800).

VBATT: Battery voltage.

VDIG: DC voltage for the processor and memory.

VDSP: DC voltage for the DSP (Digital Signal Processor).

VLCD: DC voltage for the display that controls the contrast.

VRAD: DC voltage for the radio part except the synthesizer.

VRPAD: DC voltage for the radio part in D600 (also used for the top diode and

the buzzer).

VRTC: DC voltage for the real time clock.

VSIMPAD: VDIG voltage that has been switched up to 5V used for SIM.

VVCO: DC voltage for the synthesizer.

I2C: Two line serial communications standard using one clock and one data

line.

LO: Local oscillator.

PWM: Pulse width modulation.

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1.3 Pin placements

Single diode (PIN diode). Electrolytic capacitor.

Double diode or single trans-

stor. Five pin circuit (usually volt-

age regulator). Double transistor.

Eight pin circuit. Tx VCO circuit (G300) LO VCO circuit (G350)

Sixteen pin circuit Twenty pin circuit Crystal

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N800 D900

D600

D620 D610

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2 No serv/not able to connect calls.

2.1 Finding out if the fault is Rx- or Tx-related.

Connect the phone (with signalling program) to a GSM test instrument and try to

get serv at –68.5dBm signal strength.

• If the phone doesn’t get serv, proceed to section 2.2.

• If the phone gets serv, proceed to section 2.3.

2.2 The phone doesn’t get serv.

Open the phone and check for liquid damages.

Make sure the back cover is intact and that it’s of the right model since there are two

models available. Fig. 2.1 shows which back cover model to use.

Fig. 2.1

Replace the antenna connector and try again. Note that there are several models of

the antenna connector and it’s important not to mount the wrong model. Fig. 2.2

shows which antenna connector model is to be used.

Fig. 2.2

PF768, Standard Electrical Repairs

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• If the phone gets serv, proceed to section 2.3.

• If the phone doesn’t get serv there is probably a LO-part fault or the losses in the

signal path are too great. It’s also possible it could be a feed voltage fault.

If the fault remains, send the phone to the next level.

2.3 Connect a call towards the GSM test instru-

ment at power level 0 and –68.5dBm input

signal strength.

If you’re able to connect a call, proceed to section 2.4.

If you’re not able to connect a call, open the phone and check for liquid damages.

Make sure the back cover is intact and of the correct model since there are 2 models

(ﬁg. 2.1).

Replace the antenna connector (if you haven’t replaced it already) and try again.

Note that there are several different models of the antenna connector too and it’s

important to mount the correct one.

• If you where able to connect a call, proceed to section 2.4.

The fault is probably Tx related or it’s a feed voltage fault if you still aren’t able to

connect calls.

If the fault remains, send the phone to the next level.

2.4 Read the Rx-level value from the instru-

ment while the call still is connected.

If the Rx-level value is at 42 2 steps, make sure the output power is 28-32dBm.

• The phone probably isn’t faulty if that’s correct.

Lower the signal from the instrument to –102.5dBm and make sure the Rx-level

value is 4-12 steps and that the Rx-quality value is 0-2 steps.

Try running the phone through the test again.

• If the phone passes the test but isn’t able to connect a call towards the “real” net,

make sure the phone hasn’t been locked out of the system due to theft. If it

hasn’t, replace D600 (class B, ﬁg. 2.3).

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Fig. 2.3

If the output power is too low or if the Rx-quality value or the RX-level vaule is too

high, send the phone to the next level.

If the Rx-level value is below 39 steps at –68.5dBm input signal strength or below 4

steps at –102.5dBm input signal strength, then the fault is Rx-related.

Open the phone and check for liquid damages.

Make sure the back cover is intact and that it’s of the right model since there are two

models available. Fig. 2.1 shows which back cover model to use.

Replace the antenna connector and try again. Note that there are several models of

the antenna connector and you must mount the correct model. Fig. 2.2 shows which

antenna connector model is to be used.

If the fault remains, send the phone to the next level.

Indice

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