Sony-Ericsson K750 Service Manual Trouble Shooting

Trouble Shooting Guide, Mechanical

Trouble Shooting Guide, Mechanical

Applicable for K750

Contents

1

2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

General...........................................................................................2

1.1. Service functions in the software....................................2

1.2. Misuse and other no warranty issues.............................3

Appearance Problems....................................................................6

Network/Signal Problems ...............................................................9

On/Off Problems...........................................................................10

Audio Problems ............................................................................12

Key Problems ...............................................................................16

Display Problems..........................................................................19

Illumination Problems ...................................................................21

Alert Problems..............................................................................23

SIM Problems...............................................................................25

Charging/Capacity Problems........................................................26

Camera Problems.........................................................................27

Data Communication Problems....................................................30

Hands-Free Problems...................................................................32

Software Problems .......................................................................32

Revision History............................................................................33

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Trouble Shooting Guide, Mechanical

1 General

This document outlines the mechanical repairs that should be made in an attempt to fix the common failures that are seen in the field. To gain a
complete understanding of how to test and repair a specific failure, this document should be used in conjunction with the Test Instructions,
Mechanical and the Working Instructions, Mechanical.

1.1. Service functions in the software

The service menu will be accessed with the following key combination. Use the joystick.

⇒*⇐⇐*⇐*

They are as follows:

Service info
Service tests
Text labels

The phones software has a built in service functionality that allows you to test some of the phones functions. (See point 2 above) It looks like this:

Main display
LED/illumination
Keyboard
Speaker
Earphone
Microphone
Vibrator
Camera
Flash LED
Memory Stick
Real time clock
FM radio (You need a headset to test)
Total call time

NOTE: Different names may occur depending on language setting and customization.

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1.2. Misuse and other no warranty issues

Misuse is not covered by warranty. This chapter will explain what’s not covered by warranty. Phones that have been exposed to misuse will not
be covered by warranty.

This means: if it is possible to repair the phone, the customer will have to pay for the repair. SEMC will not allow any of these phones to be
claimed into WCMS. Some local perspectives may interfere with this. Please reference to local directives.

1.1.1 Action

Make a general visual inspection for misuse.
Below are some examples of what is not covered by warranty.

Front window broken due

to misuse.

Corrosion components on the PCB. Corrosion components on the PCB. SIM reader damaged by liquid. System connector damaged by liquid

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LCD cracked due to

drop.

Clear scratches Mark after drop

Corrosion components on

the PCB.

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Components around system
connector damaged by liquid

System connector pad(s) damaged
by liquid

1.1.2 Liquid damage sticker

In the phone there is placed a sticker that can give you a hint to see if the phone is damage by liquid or not. This sticker is located near the SIM
reader (Fig. 1.2.1) and it is possible to see it without disassemble the phone.

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Fig. 1.2.1

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On the pictures below you will see the different between a sticker that has been in contact with liquid (Fig. 1.2.3) and with one that hasn’t (Fig.

1.2.2).

This sticker is ok This sticker is not

1.1.3 Action

Make a general visual inspection for misuse, corrosion or oxidation from liquid damage. No further action should be taken for a liquid damaged
phone. Handle the unit according to local directives.

Fig. 1.2.2 Fig. 1.2.3

ok

The white sticker that has been in contact with
liquid turns into a red or pink sticker. In this case
you should check the phone for liquid damage
(See point 1.1.1).

Note: There must be clear marks after liquid on the
PCB before rejecting the phone for repair.

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2 Appearance Problems

Problem Area Items to Check Repair Action Reference Image

Appearance

Visually inspect the cosmetic quality of all
user viewable surfaces

Front
System connector
Joystick button
Frame assembly
IRDA window
Memory card rubber lid
Antenna cover assembly
Battery cover assembly
Co-brand inlay

• If dirty – Clean parts as necessary.

• If unacceptably scratched or damaged –

Replace damage parts as necessary.

NOTE: Misuse is not covered by warranty.
Refer to chapter 1.2

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Problem Area Items to Check Repair Action Reference Image

Visually inspect all keys
Keyboard

On/Off key
Music key
Volume key
Camera key

• If dirty – Clean parts as necessary.

• If unacceptably scratched or damaged –

Replace damaged parts as necessary.

NOTE: Misuse is not covered by warranty.
Refer to chapter 1.2

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Trouble Shooting Guide, Mechanical

Problem Area Items to Check Repair Action Reference Image

Visually inspect for improper gap between
seams

• Reassemble or replace damaged parts as
necessary.

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Trouble Shooting Guide, Mechanical

3 Network/Signal Problems

Problem Area Items to Check Repair Action Reference Image

No Signal or Poor
Signal

Before proceeding ! Perform a flash upgrade.
Visually inspect SIM holder

Visually inspect antenna contact pads

• If dirty or oxidized – Clean it.

• If damaged – Send to an electrical repair

location.

• If dirty or oxidized – Clean the pads and
replace the antenna assembly.

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Problem Area Items to Check Repair Action Reference Image

Visually inspect antenna

• If dirty or oxidized – Replace it.

• If damaged – Replace it.

If the issue has not been resolved !

4 On/Off Problems

Problem Area Items to Check Repair Action Reference Image

Power On problems

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Check whether the phone vibrates 10 to 15
seconds after pressing the power key and
whether the keypad illuminates

Before proceeding !

• Handle the unit according to local
directives.

• If activation of the vibrator and keypad are
detected, refer to the “Display Problems”
section

• Perform a flash upgrade.

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Trouble Shooting Guide, Mechanical

Problem Area Items to Check Repair Action Reference Image

Visually inspect contact pads on battery

Visually inspect battery connector

Visually inspect the power key

• If dirty or oxidized – Clean pads.

• If damaged – Replace it.

• If dirty or oxidized – Clean it.

• If damaged – Send to an electrical repair

location.

• If damaged – Replace it.

If the issue has not been resolved !

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• Handle the unit according to local
directives.

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5 Audio Problems

Problem Area Items to Check Repair Action Reference Image

Microphone:

Before proceeding !

• Perform a flash upgrade and a setting
reset.

Visually inspect the microphone’s external
port

Visually inspect the microphone’s dust
cloth

If the issue has not been resolved !

• If clogged - Clean or replace frame
assembly.

• If dirty or damaged – Replace frame
assembly.

• Handle the unit according to local
directives.

Speaker:
No sound or poor

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Before proceeding !

• Perform a flash upgrade and a setting
reset.

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Trouble Shooting Guide, Mechanical

Problem Area Items to Check Repair Action Reference Image

quality sound

Visually inspect speaker’s external port

Visually inspect speaker’s dust cloth

• If clogged – Clean or replace front
assembly.

• If dirty or damaged – Replace front cover.

Visually inspect the speaker’s contact pads
on the PCB

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• If dirty or oxidized- Clean pads.

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Problem Area Items to Check Repair Action Reference Image

Visually inspect the speaker pins

• If damaged, dirty or oxidized – Replace
speaker box.

No sound or poor
quality sound

If the issue has not been resolved !

If the issue has not been resolved !

Before proceeding !

Visually inspect speaker’s external port

• Replace speaker box.

• Handle the unit according to local

directives.

• Perform a flash upgrade and a setting
reset.

• If clogged – Clean or replace antenna
cover.

Poly.-Speaker:

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Problem Area Items to Check Repair Action Reference Image

Visually inspect the speaker’s dust cloth

Visually inspect the speaker’s contact pads
on the PCB

• If dirty or damaged - Replace antenna
cover.

• If dirty or oxidized- Clean pads.

Visually inspect the speaker pins

If the issue has not been resolved !

If the issue has not been resolved !

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• If damaged, dirty or oxidized – Replace
speaker box.

• Replace speaker box.

• Handle the unit according to local

directives.

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Trouble Shooting Guide, Mechanical

6 Key Problems

Problem Area

Keyboard:
A key on the

keyboard is not
functioning or is
intermittent

Items to Check

Visually inspect for debris between
keyboard and keyboard foil, and for
damage to the keyboard and the keyboard
foil.

NOTE: Camera switch is located on the
keyboard foil.

NOTE: Camera switch is a dual switch.

Repair Action

• If dirty – Clean both parts.

• If damaged - Replace keypad and/or

keyboard foil as necessary.

Reference Image

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Trouble Shooting Guide, Mechanical

Problem Area

Items to Check

Visually inspect whether the keyboard flex
film is properly connected to its connector

Repair Action

• If improperly connected – Re-establish
proper connection.

Reference Image

on the PCB

If the issue has not been resolved !

• Replace the keyboard foil, if it has not
already been replaced.

If the issue has not been resolved !

Joystick: Visually inspect the joystick button

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• Handle the unit according to local
directives.

• If dirty or damaged – Replace it.

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Trouble Shooting Guide, Mechanical

Problem Area

Side keys

Items to Check

Visually inspect for damage to the side keys

Repair Action

• If damaged - Replace keys as necessary.

Reference Image

Volume keys
Music key
Camera key
On/Off key

If the issue has not been resolved !

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• Handle the unit according to local
directives.

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Trouble Shooting Guide, Mechanical

7 Display Problems

Problem Area

LCD problem

Items to Check

Check whether the phone vibrates 10 to 15
seconds after pressing the power key and
whether the keypad illuminates

Before proceeding !
Visually inspect whether the LCD flex film

is properly connected to its connector on
the PCB

Repair Action

• If activation of the vibrator are not
detected, refer to the On/Off Problems”

chapter 2

• Perform a flash upgrade and a setting reset.

• If improperly connected – Re-establish

proper connection.

Reference Image

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Problem Area

Items to Check

If the issue has not been resolved !

Repair Action

• Replace the LCD.

Reference Image

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8 Illumination Problems

Problem Area

Keys:
The entire keypad

or a portion of the
keypad does not
illuminate.

Items to Check

Before proceeding !
Visually inspect whether the keyboard

flex film is properly connected to its
connector on the PCB

Visually inspect the keyboard foil.

If the issue has not been resolved !

Repair Action

• Perform a flash upgrade and a setting reset.

• If improperly connected – Re-establish proper

connection.

• If dirty or oxidized – Replace it.

• If damaged – Replace it.

• Replace the keypad and the keyboard foil.

Reference Image

If the issue has not been resolved !

LCD Before proceeding !

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• Handle the unit according to local directives.

• Perform a flash upgrade and a setting reset.

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Trouble Shooting Guide, Mechanical

Problem Area

Items to Check

Visually inspect whether the LCD flex
film is properly connected to its

Repair Action

• If improperly connected – Re-establish proper
connection.

Reference Image

connector on the PCB

If issue has not been resolved !

• Replace the LCD.

If the issue has not been resolved !

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• Handle the unit according to local directives.

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Trouble Shooting Guide, Mechanical

9 Alert Problems

Problem Area

Vibrator:

Poly.-Speaker: Before proceeding !

Items to Check

Before proceeding !
Visually inspect the vibrator contact

pads on the PCB

Visually inspect the vibrator

Repair Action

• Perform a flash upgrade and a setting reset.

• If dirty or oxidized – Clean them.

• If dirty or oxidized – Replace it.

• If damaged - Replace it.

• Perform a flash upgrade and a setting reset.

Reference Image

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Trouble Shooting Guide, Mechanical

Problem Area

No sound or poor

Items to Check

Visually inspect speaker’s external port

Repair Action

• If clogged – Clean it.

Reference Image

quality sound

Visually inspect the speaker’s dust cloth

• If dirty or damaged - Replace antenna cover.

Visually inspect the speaker’s contact
pads on the PCB

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• If dirty or oxidized- Clean pads.

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Problem Area

Items to Check

Visually inspect the speaker pins

Repair Action

• If damaged, dirty or oxidized – Replace speaker
box.

Reference Image

If the issue has not been resolved !

If the issue has not been resolved !

10 SIM Problems

Problem Area

SIM undetected
(Insert SIM)

Unit indicates the
incorrect SIM is
inserted (Insert

correct SIM)

Items to Check

Inspect SIM holder

Check whether the phone is locked to a
particular carrier and whether the correct
carrier’s SIM is being used

If the issue has not been resolved !

• Replace speaker box.

• Handle the unit according to local directives.

Repair Action

• If dirty or oxidized – Clean.

• If damaged – Send to an electrical repair

location.

• Use Correct Carrier SIM or test SIM.

• Handle the unit according to local directives.

Reference Image

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Trouble Shooting Guide, Mechanical

11 Charging/Capacity Problems

Problem Area

Battery will not
charge

Items to Check

Visually inspect the contact pads of the
battery

Visually inspect the of the battery
connector

Visually inspect the system connector

Repair Action

• If dirty or oxidized – Clean.

• If damaged – Replace battery.

• If dirty or oxidized – Clean.

• If damaged – Send to an electrical repair

location.

• If dirty or oxidized – Replace the system
connector.

• If damaged – Replace the system connector.

Reference Image

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Trouble Shooting Guide, Mechanical

Battery looses
charge quickly/
standby time seems
short

Before proceeding !

NOTE: Some features noticeably
reduce the amount of standby time if
they are turned on. Some examples

• Perform a flash upgrade and a setting reset.

are the back light (when on all the
time and), Bluetooth, and infrared.

If the issue has not been resolved !
If the issue has not been resolved !

12 Camera Problems

Problem Area Items to Check Repair Action Reference Image

Lines, marks,
blurred or
discolored picture

Visually inspect the camera lens

• Replace battery.

• Handle the unit according to local directives.

• If dirty – Clean camera lens.

• If scratched or damaged – Replace the camera

module.

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Problem Area Items to Check Repair Action Reference Image

Visually inspect whether the camera flex
film is properly connected to its
connector on the PCB and on the camera

• If improperly connected – Re-establish proper
connection.

Visually inspect camera flex film

If the issue has not been resolved !

Visually inspect for debris between

image

and/or damage to the camera key and the
keyboard foil.

Visually inspect whether the keyboard
foil is properly connected to its
connector on the circuit board

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• If dirty or oxidized – Replace it.

• If damaged – Replace it.

• Replace the camera module and the camera

flex.

• If dirty – Clean both parts.

• If damaged - Replace the camera key and/or the

keyboard foil as necessary.

• If improperly connected – Re-establish proper
connection.

Will not capture an

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Problem Area Items to Check Repair Action Reference Image

Visually inspect whether the camera flex
film is properly connected to its
connector on the PCB and on the camera

• If improperly connected – Re-establish proper
connection.

If the issue has not been resolved !

If the issue has not been resolved !

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• Replace the keyboard foil if it has not already
been replaced.

• Replace camera module.

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Problem Area Items to Check Repair Action Reference Image

If the issue has not been resolved !

• Handle the unit according to local directives.

13 Data Communication Problems

Problem Area Items to Check Repair Action Reference Image

Problem
transferring data
using a direct
connection

Will not connect
with a functional
IR device

Visually inspect the system connector

Visually inspect the IRDA window for
dirt, scratches, and damage

• If dirty or oxidized – Replace it.

• If damaged – Replace it.

• If dirty – Clean it.

• If damaged – Replace it.

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Will not connect
with a functional

Visually inspect the Bluetooth antenna
contact pads on the PCB

• If dirty or oxidized – Clean it.

Bluetooth device

Visually inspect the Bluetooth antenna

• If dirty or oxidized – Replace it.

• If damaged – Replace it.

If the issue has not been resolved !

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• Handle the unit according to local directives.

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14 Hands-Free Problems

Problem Area Items to Check Repair Action Reference Image

Hands-free not
working

Visually inspect the system connector

If the issue has not been resolved !

• If dirty or oxidized – Replace it.

• If damaged – Replace it.

• Handle the unit according to local directives.

15 Software Problems

• If there are problems with the response of the keypad commands, or spelling errors in the menu, if they are not related to mechanical damage,
make a master reset and flash the phone with the latest software from EMMA III.

• Checking the software revision can be done in the Service info, see chapter Service functions in the software.
Choose: Service info / SW information.
The Software revision and date will be shown in the display.

Note: Do a SW upgrade before sending the unit to a higher level. Do not

If the failure still occurs, handle the unit according to the local directives.

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scrap a phone that hasn’t been upgraded.

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16 Revision History

Rev. Date Changes / Comments

A 2005-05-13 First draft
B 2005-05-17 Due to system problem
C 2005-05-19 Due to system problem

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