1-2
THEORY OF OPERATION
When the radio is turned on, SWB+ is present and is applied to:
■
transistor switch Q494 (pins 1 and 6) which turns on Q493
■
RX audio power amplifier U490
■
voltage divider R420/R421 and port PE0, a microprocessor A/D input which measures battery
voltage and radio on/off status
The output of FET switch Q493 is applied to the control pins of regulators U310, U320 and U330,
turning them on. The following regulators are used:
The 5V source is applied to:
■
RX back end circuitry
■
synthesizer super filter input and charge pump supply
■
RED/GRN LEDs
■
RX audio buffer U510
■
portions of ASFIC U451
The 5V source is also applied to FET switches Q311 and Q312. Q311 is turned on by Q313 when
RX_ENA (from U401 pin 49) is high, and supplies the "5R" source to the RF front end stages Q21-
Q22, and the VCO RX injection buffer Q280. Q312 is turned on by Q313 when TX_ENA (from U401
pin 50) is high, and supplies the "5T" source to the first transmitter stage Q100.
The digital 3.3 volt source from U320 (D_3.3V) is applied to:
■
microprocessor U401
■
EEPROM U402
■
S-RAM U403 (not used)
■
flash ROM U404
The 3V regulated source from U330 is applied to:
■
synthesizer IC U201
■
VCO/buffer IC U251
■
portions of ASFIC U451
■
microphone bias circuitry
While the radio is turned on, port PH3 (U401 pin 44) is held high. When the radio is turned off,
SWB+ is removed and port PE0 (U401 pin 67) goes low, initiating a power-down routine. Port PH3
(pin 44) remains high, keeping the voltage regulators on via Q493 and Q494, until the operating
state of the radio has been stored in EEPROM and other turn-off data functions have been
completed. PH3 then goes low, turning off Q494 and Q493, and all regulated voltages are removed.
Table 1-1
Voltage Regulators
Reference No.
Description
Type
U310
5V Regulator
TK71750S
U320
Digital 3.3V Regulator
LP2986
U330
3V Regulator
TK71730S
Summary of Contents for CP 140
Page 1: ...Commercial Series CP140 CP160 CP180 Portable Radios Detailed Service Manual 6866550D20 O ...
Page 2: ...ii ...
Page 4: ...iv ...
Page 12: ...viii ...
Page 28: ...iv ...
Page 40: ...1 12 THEORY OF OPERATION ...
Page 48: ...2 8 TROUBLESHOOTING TABLES ...
Page 50: ...3 2 CONTROLLER KEYPAD SCHEMATICS ...
Page 58: ...3 10 Keypad Board Parts List 8466565A01 O ...
Page 62: ...iv ...
Page 66: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 90: ...3 16 TROUBLESHOOTING TABLES ...
Page 92: ...4 2 VHF PCB SCHEMATICS PARTS LISTS ...
Page 108: ...iv ...
Page 112: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 136: ...3 16 TROUBLESHOOTING TABLES ...
Page 138: ...4 2 UHF1 PCB SCHEMATICS PARTS LISTS ...
Page 154: ...iv ...
Page 158: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 182: ...3 16 TROUBLESHOOTING TABLES ...
Page 184: ...4 2 UHF2 PCB SCHEMATICS PARTS LISTS ...
Page 200: ...iv ...
Page 204: ...1 4 MODEL CHART AND TECHNICAL SPECIFICATIONS ...
Page 228: ...3 16 TROUBLESHOOTING TABLES ...