Ericsson T28s - Explanations

Trouble Shooting Guide, Standard
4/00021-2/FEA 209 544/19 E 2(29)
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 ± 0.05 V
VCORE: DC voltage for the processor and memory at, for instance, stand by mode.
2.50 ± 0.10 V
VDIG: DC voltage for the processor and memory. 2.70 – 2.85 V
VDSPC: DC voltage for the DSP (Digital Signal Processor). 1.80 ± 0.10 V