Ericsson I 888 Guide

Approved according to 1776-2/FEA 209 544
Trouble-shooting
instruction
I 888
Standard electrical repairs
4-00021-2/FEA 209 544/5.C
I888, Standard Electrical Repairs

I888, Standard Electrical Repairs
4-00021-2/FEA 209 544/5.C 2(42)
Table of contents
1 Conditions .......................................................................................... 3
2 No serv or can´t place call. ............................................................... 6
3 Doesn´t start. ................................................................................... 10
4 Audio ................................................................................................ 15
5 Display fault .................................................................................... 21
6 Charging fault ................................................................................. 24
7 SIM fault (Insert card) ................................................................... 27
8 Keyboard ......................................................................................... 29
9 Illumination and buzzer. ................................................................ 33
10 RTC (Real Time Clock) .................................................................. 38
11 IRDA fault. ...................................................................................... 40
12 Component list................................................................................. 42

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1 Conditions
1.1 Component classifications.
After each component, which fault can be verified by the troubel-shooting guides in
this folder, is the components classification written. The components are divided in
four classes, A,B,C and D. The classes are seperated depending on how much of the
phone´s prestanda that is affected by changing the component.
Class A and B:Changing the component doesn´t affect the prestanda that much,
you only have to do a test call toward a real network before you perform a function
test after replacing it.
Class C: The phone has to be calibrated at station level after changing the com-
ponent, since the components tolerances are so large it can affect the prestanda of
the phone.
Class D: It demands advanced equipment and calibration at board level and
because of that class D-components can´t be replaced.

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1.2 Abbreviations used in the trouble-shooting
instructions.
B: Crystal
C: Capacitor
D: Digital circuit
F: Overload protection
H: Buzzer, ligth diodes, pads to the display
J: Connection
L: Coil
N: Analouge circuit
R: Resistor
U: BALUN. Component that converts a balanced signal to a nonbalanced or the
opposit direction.
V: Transistor, diode
X: Antenna connection, contact point on the board.
Z: Filter
AGND: Ground to analouge signal
DCIO: Direct current through the system connector for charging the bat-
tery.
DCON: Logical signal from the processor that keeps the phone powered on
after releasing the On/Off-button.
GND: Ground
LED3K: Logical signal that activates the illumination.
ONSRQ: Voltage from the On/Off-button that power on the phone.
REGON: Logical signal that activates the regulator for the voltage.
RTC: Real time clock. The clock that shows the time.
SIMCONCLK: Signal from the processor that is used for communication to SIM,
clock.
SIMCONDAT: Signal from the processor that is used for communication to
SIM,data.
SIMCONRST: Signal from the processorn that is used for communication to
SIM,reset.
SIMVCC: Feed voltage to SIM.
SWDC: Switch VBATT
VANA: Voltage to the analouge part of the logical circuit (N800).

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VBATT: Voltage of the battery.
VDIG: Voltage to processor and memories (3.2V).
VDSP: Voltage to DSP (Digital Signal Processor) (3.2V).
VDSPC: Voltage to DSP (Digital Signal Processor) (2.5V).
VLCD: Negative voltage to the display that controlls the contrast (-2.7V).
VDLCD: Feed voltage to the display.
VRAD: Voltage to the radiopart except the synthesizer.
VRPAD: Voltage to the radiopart in D600 (used to top indicator and buzzer).
VRTC: Voltage to the real time clock.
VVCO: Voltage to the syntesizer.
I2C: Communication standard for two-way communication using only 2
wires, for clock and data.
LO: Local oscillator.
PWM: Puls width modulation.

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2 No serv or can´t place call.
2.1 Find out if the fault is related to
Rx(reciever) or Tx(transmitter).
Connect the phone (with signaling program) to a GSM test instrument and try to get
serv at -68.5 dBm on the input signal. If the phone gets serv proceed to section 2.2.
If the phone doesn´t get serv, there is probably a fault in the LO part or too big
losses in the signal path. Open the phone and check for liquid damages. Make sure
the antenna connection X101 (class A) isn´t mecanically damaged, unsoldered or
dirty (varnish, glue, oxide...) (Fig 2.1).
Look for soldering faults on C318 (class A), N302 and N303 (all three Fig 2.1).
Measure the resistance of C530, C531, C532, C533, C534 and C535 (>200 kOhm,
all are class A, Fig 2.1).
Measure the resistance of C850 (>100 kOhm, class A, Fig 2.1), C851 (>1 kOhm,
class A, Fig 2.1), C833 (>1 kOhm, class A, Fig 2.1) and C853 (>100 kOhm, class
A, Fig 2.1).
Measue VVCO and VRAD (3.8V, Fig 2.2). If any of the voltages are incorrect, pro-
ceed to chapter 3 (“Doesn´t start”-fault).
Fig 2.1
X101
C530
C534
C531
C533
C535
C532
1
89
20
N303
N302
C318
N301
C853
C850
C851
C833
1
3
4
6

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Measure the voltage on pin 4 and 6 on N303 (Fig 2.1). The voltage on pin 4 (the
control voltage) should always vary between 0.8-2.8 V (usually it starts at 1.7 V).
The voltage on pin (the feed voltage) is also variable, but usually it starts at 3.3 V. If
the feed voltage is incorrect (often is it missing completly), check the solderings on
D600:8, D600:102 and also on D105 and D103 (all at Fig 2.2). If the control voltage
is incorrect (mainly 0 or 3.6 V), check the solderings on D600:8 and D600:106-108.
If those are fine, replace N301 (class B, Fig 2.1).
Check the solderings on Z250, Z500, Z201 (GSM 900) and Z202 (GSM1900) (all at
Fig 2.2) plus Z205 (Fig 2.3).
If the fault still remains, send the phone to the next repair level.
Fig 2.2
VVCO
VRAD Z201
Z202
Z250
Z500
D103
N401
L403
N570
N560
L560
B510
D600
D105
1
1
32
33
64
65
96
97
128
1
28
14
15
Fig 2.3
Z204
Z205
Z203
L223
P401

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2.2 Connect a call.
To test GSM900,connect a call at power level 5 against the instrument with the input
signal at -68.5 dBm. To test GSM1900 use power level 0 and an input signal at -68.5
dBm.
If it works, proceed to section 2.3. If it doesn´t work, then it probably is a TX related
fault. If it is only at channel 1 (or several of the lower channels) you can´t connect a
call, is it N570 (class D, Fig 2.2) that is faulty and the phone can´t be repaired at this
level. Open the phone and check for liquid damages. Make sure the antenna connec-
tion X101 (class A, Fig 2.1) isn´t mecanically damaged, unsoldered or dirty (var-
nish, glue, oxide...).
Measure the resstance between test point P401 (Fig 2.3) and ground (or between
N401:14 (Fig 2.2) and ground). The resistance should be larger than 5 kOhm. If it is

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900) and Z202 (GSM1900)(all at Fig 2.2) plus Z205 (Fig 2.3). If the fault still
remains, send the phone to the next repair level.
If the Rx level value is above 45 steps at input signal -68,5 dBm you need to cali-
brate the phone, therefore send the phone to the next repair level.
If the RX quality value is too high, send the phone to the next repair level.
If the output power is too low, check the solderings on N560 (GSM1900) and N570
(GSM900) (both Fig 2.2). Check the solderings on Z205, Z203 (GSM900) and
Z204 (GSM1900)(all three Fig 2.3). If the fault still remains, send the phone to the
next repair level.

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3 Doesn´t start.
3.1 Find out if the phone will start by using the
On/Off-button.
Attach a fully charged battery and press the On/Off-button. If the phone doesn´t
start, proceed to section 3.2. If the phone starts as normal when it is complete, but
shuts down in the trouble-shooting fixture, measure the current consumption. If it is
>1.5 A or as high as the current limit on the power supply, then N401 (class D, fig
3.1) is faulty and the phone can´t be repaired at this repair level. (Measure the resist-
ance between N401:14 and ground, it should be >10 kOhm, but if N401 is faulty it
usually is about 200 Ohm).
If the phone starts, check the charging function by connecting a charger at the sys-
tem connector.If the charging doesn´t work, proceed to chapter 6 (“Charging”-
fault). Open the phone and make a visual check of the board. The side with the com-
ponents are shown in fig 3.1. Check the board for liquid damages and burned or dan-
ages pads at the system connector. Measure the resistance of R421 (0,1 Ohm, class
B, fig 3.1). After every repair of the charging function, you have to verify the
function using the method mentioned in section 6.1.1. Check the solderings on
D600 and D610 (Fig 3.1). As soon as the fault has been corrected, send the phone
back into the normal repair flow. If the phone starts and the values above are correct,
it is either without faults or there is an intermittent fault.
Fig 3.1
N401
N412
N410
N411
N701
VDSP
VVCO
VRPAD
VRAD
VDIG
C692
D600
N702
D610
N703R725C710
B510
1
1
32
33
64
65
96
97
128
R421
1
14
15
28