Service Manuals, User Guides, Schematic Diagrams or docs for : . Rare and Ancient Equipment Ericsson Mobile Phones ERICSSON T28 ERICSSON T28 5 T28s-instr-serwis
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Trouble Shooting Guide, Standard
Trouble Shooting Guide, Standard
Applicable for T28s and T28sc
Contents
1 Explanations ....................................................................................................................2
2 Network Problems...........................................................................................................5
3 On/Off Problems ...........................................................................................................10
4 Audio Problems .............................................................................................................13
5 Display/illumination problems.....................................................................................17
6 Capacity/Charging Problems.......................................................................................21
7 SIM Problems................................................................................................................22
8 Key/Flip Problems.........................................................................................................23
9 Alert Problems...............................................................................................................25
10 Data Communication Problems...................................................................................27
11 Software Problems ........................................................................................................27
12 Other Problems .............................................................................................................28
13 Revision History ............................................................................................................29
4/00021-2/FEA 209 544/19 E Approved according to 1776-2/FEA 209 544
Trouble Shooting Guide, Standard
1 Explanations
For component placing see doc.1078-2/FEA 209 544/19.
Repeated Tests:
When the front has been removed most of the tests can be performed without the front
mounted.
1.1 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, power amplifier at some phones.
R: Resistor.
S: Keyboard pads.
U: BALUN Component that converts a balanced signal to an unbalanced or the other way
around.
V: Transistor, diode.
X: Contact surface on the circuit board.
Z: Filter.
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 the track of time.
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, reset signal.
SIMVCC: Feed voltage for SIM.
VBATT: Battery voltage. 3.70 ◦ Jabse Service Manual Search 2026 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo