Theory Of Operation; General Information; Power Distribution; Power Up Sequence - Motorola GP2000 Service Manual

7-4
3.0

Theory of Operation

3.1

General Information

Your radio has two printed circuit boards: the Controller board, and the Radio Frequency (RF)
board. The Controller board contains the CPU/Control section. The RF board contains the VCO/
Synthesizer section, Transmitter section, Receiver section, Transmitter Audio circuitry, Receiver
Audio circuitry, and Battery section.
3.2

Power Distribution

RF PA Driver AMP
Q411 Q412
Battery
The above Þgure illustrates the DC distribution throughout the radio board. A battery supplies power
directly to the electronic on/off control. Radio power supply is triggered by the Power Switch (On/
Off/Volume control) and +SW B is distributed as show in the Þgure. Regulator output 5V is supplied
to the CPU. +SW B continues to support the Audio Power AMP, 5V Regulator, TX Regulator until
the radio is turned off.
The radio can be turned off on two ways:
1. Power Switch turned-off
2. Low Battery
When a low battery level is detected by the CPU, it stores the radio personality data to EEPROM
before turning off the radio.
3.3

Power up Sequence

1. Power supply is turned on by the On/Off/Volume Control (Power Switch).
2. Power from battery is supplied to the regulator through the switch.
3. Output (5V) from the regulator is directed to the CPU (Q101).
4. Q105 resets the CPU (Q101).
5. The CPU loads radio personality data from EEPROM after the reset.
Audio Power
AMP
Q702
SAVE SW
+ SW B
Q210
Power
5V REG
Switch
Q204
SW201
VCO Buffer PLL IC Ripple Filter
Q308 Q323 Q330
RF AMP Local AMP
Q404 Q416
RX SW
Q211
TX/RX SW
Q210,211
MIC AMP Sub Audio
Q602 LPF Q610
TX REG
Q201,202
Reset CPU EEPROM
Q105 Q101
Diode
Q126
Theory of Operation
TX/RX SW TX VCO
Q309,310 Q325
RX VCO
Q324
IF AMP IF AMP LPF
Q408 Q506 Q502
RF Power
TX Driver
Control
Q413,414
Q419
TX +5V
Divide DA
by 2 Converter
Q114
Q122 Q121
HPF
Q505
RX +5V
DTMF
Decode
Q120