Radio Shack TRC-447 User manual

TRC-447

40-CHANNEL MOBILE CB

WITH WX ALERT

Catalog Number: 21-1576

CONTENTS

Page

Specifications ................................................................................................................................................. 2

Block Diagram ................................................................................................................................................ 5

Alignment and Adjustment ............................................................................................................................. 6

Troubleshooting ........................................................................................................................................... 10

Wiring Diagram ............................................................................................................................................ 16

Printed Circuit Boards .................................................................................................................................. 17

Exploded View and Disassembly Instructions.............................................................................................. 20

Mechanical Parts List ................................................................................................................................... 23

Electrical Parts List ...................................................................................................................................... 24

Semiconductor Lead Identification ............................................................................................................... 43

IC Internal Diagrams .................................................................................................................................... 44

IC and Transistor Voltage Chart................................................................................................................... 46

Schematic Diagrams .................................................................................................................................... 50



2004 RadioShack Corporation.

RadioShack is a registered trademark of RadioShack Corporation.

21-1576

— 2 —

SPECIFICATIONS

GENERAL

Channels: 40 (CB Transceiver)

7 (Digital Weather Alert Radio)

Frequency range: 26.965 MHz to 27.405 MHz (CB)

162.400 MHz to 162.550 MHz (WX)

Frequency control: PLL controlled synthesizer

Microphone: Electret condenser type microphone with channel up/down switch

Antenna impedance: 50-ohm

Controls: Volume control with Power on/off Switch

Squelch control for CB

SWR Cal Control for CB

RF gain control for CB

Mic Gain Control for CB and PA

Switches: CH9-NOR-CH19 Lever Switch for CB

S/RF-SWR-CAL Lever Switch for CB

CB-WX-PA Lever Switch

NB-OFF-MON Lever Switch

DUAL-OFF Lever Switch for CB

Channel Rotary Switch for CB and WX

Indicators: Channel number (LED: Green color)

TX/RX (LED:TX-Red/RX-Green Color)

WX/ALERT (LED:Red Color)

Antenna connector: M Type (SO 239)

Jacks: Mic 6 pin Screw Type

EXT. SP 3.5 dia.

PA. SP 3.5 dia.

Dimensions (HWD): 55mm ×185 mm ×225 mm

Weight: 1.4 kg

Power supply: 12 V DC rated (13.8 V DC)

Operating temperature range: −30 °C to +50 °C (FCC Stability)

Storage temperature range: −30 °C to +60 °C (Without damage)

Accessories: Microphone

Microphone hanger with screws

Mounting bracket with screws

DC Power Cord with Fuse

Owner's manual

Measuring Conditions

Power supply voltage: 13.8 V DC

Temperature and humidity: 25 ±5 °C, 50 to 70%

Output load for transmitter: 50 ohm Resistive

Input signal source: 50 ohm SSG

Test input signal: 1 kHz, 30% Modulation (CB)

1 kHz, ±3 kHz Deviation (WX)

FSK, ±4.5 kHz Deviation (Digital WX Alert)

Output Load for Receiver: 8 ohm Resistive

Reference Audio Output Power: 0.5 W

Measuring Channel: CH 20 (CB)

CH 5 (WX)

Each Function Knob Condition.

Volume: Fully clockwise (FCW)

Squelch: Unsquelched

RF gain: Fully clockwise (FCW)

Mic Gain: Fully clockwise (FCW)

CH9-NOR-CH19: NOR

NB-OFF-MON: OFF

DUAL-OFF: OFF

✽FCC type acceptance specification for PART 15 and 95.

✽Frequency tolerance and specification: ±0.005% from −30 °C to +50 °C

— 3 —

CB TRANSMITTER PORTION

Item Unit Nominal Limit

Frequency tolerance 25 °C 13.8 V Hz ±200 ±1300

RF Power output W −4

AMC range 50% to 100% modulation dB 45 35

Modulation frequency response Lower frequency 450 Hz dB −3−10

Upper frequency 2500 Hz dB −3−10

Microphone sensitivity 1 kHz, 50% Mod. mV 4 10

Modulation distortion 1 kHz, 80% Mod. % 3 8

Battery drain at No modulation mA 900 1300

at 80% modulation mA 1300 1900

RF Power output at 12 V W 2.7 2.2

Modulation attack time mSec 100 300

Modulation release time mSec 800 500

CB RECEIVER PORTION

Maximum sensitivity µV 0.5 1

Sensitivity for 10 dB S/N µV 0.5 1

AGC Figure of merit 50 mV for 10 dB change in audio output dB 90 75

Threshould squelch sensitivity µV 0.5 1

Tight squelch sensitivity µV 1000 250 ~ 4000

Adjacent channel selectivity at ±10 kHz dB 50 40

Spurious rejection ratio dB 45 30

Image rejection ratio (−910 kHz) dB 65 55

IF rejection ratio 10.695 MHz dB 60 50

455 kHz dB 90 60

Audio output power Maximum 8-ohm W 5.5 4.0

10% Distortion 8-ohm W 4.0 3.5

Audio frequency response Lower frequency 450 Hz dB −3-10

Upper frequency 2500 Hz dB −3-10

THD at 500 mW audio output 1 mV 30% input % 3 5

Signal to noise ratio at 1mV dB 40 35

Oscillator on voltage V 5 11

Battery drain at No signal mA 300 350

at Maximum AF output mA 1000 1500

RF gain control range at 1 µV reference dB 30 20

S-meter sensitivity at S-9 µV 100 50 ~ 200

WEATHER RADIO SECTION

Sensitivity at 2.0 µV Input dB SINAD 27 15

THD at 500 mW audio output

Input 1 mV ±3 kHz deviation % 3 7

Signal to noise ratio at 1 mV dB 45 35

Audio output power Maximum 8-ohm W 5.5 4

10% Distortion 8-ohm W 4 3.5

Digital weather alert sensitivity

Input SAME data (FSK) ±4.5 kHz dev. µV 0.5 1.0

— 4 —

CHANNEL FREQUENCY OF PLL SYNTHESIZER

CB BAND

Antenna

Frequency

(MHz)

TX VCO

Frequency

(MHz)

RX VCO

Frequency

(MHz)

1 26.965 26.965 16.270

2 26.975 26.975 16.280

3 26.985 26.985 16.290

4 27.005 27.005 16.310

5 27.015 27.015 16.320

6 27.025 27.025 16.330

7 27.035 27.035 16.340

8 27.055 27.055 16.360

9 27.065 27.065 16.370

10 27.075 27.075 16.380

11 27.085 27.085 16.390

12 27.105 27.105 16.410

13 27.115 27.115 16.420

14 27.125 27.125 16.430

15 27.135 27.135 16.440

16 27.155 27.155 16.460

17 27.165 27.165 16.470

18 27.175 27.175 16.480

19 27.185 27.185 16.490

20 27.205 27.205 16.510

21 27.215 27.215 16.520

22 27.225 27.225 16.530

23 27.255 27.255 16.560

24 27.235 27.235 16.540

25 27.245 27.245 16.550

26 27.265 27.265 16.570

27 27.275 27.275 16.580

28 27.285 27.285 16.590

29 27.295 27.295 16.600

30 27.305 27.305 16.610

31 27.315 27.315 16.620

32 27.325 27.325 16.630

33 27.335 27.335 16.640

34 27.345 27.345 16.650

35 27.355 27.355 16.660

36 27.365 27.365 16.670

37 27.375 27.375 16.680

38 27.385 27.385 16.690

39 27.395 27.395 16.700

40 27.405 27.405 16.710

WX/ALERT BAND

Antenna

Frequency

(MHz)

VCO

Frequency

(MHz)

1 162.400 151.705

2 162.425 151.730

3 162.450 151.755

4 162.475 151.780

5 162.500 151.805

6 162.525 151.830

7 162.550 151.855

— 5 —

BLOCK DIAGRAM

— 6 —

DC Voltmeter

Set

PTT

MIC

JACK

ANT

J501

J751

Dummy Load

(50-ohm)

And Attenuator

ALIGNMENT AND ADJUSTMENT

ALIGNMENT OF PLL

Test Equipment Required and Connections

•DC power supply: 13.8 V •DC voltmeter •Dummy load (50-ohm)

Alignment Point Locations (Main PCB)

Alignment Procedure

Step Preset to Adjustment Remarks

1 TX 40 CH L301 Adjust L301 to obtain 3.8 ±0.1 V (DC) at TP3 (R304).

2 TX/RX 1 ~ 40 CH — Check if the DC Voltage on all channels is kept within

1.5 V to 3.9 V at TP3.

3 RX 40 CH CT301 Adjust CT 301 to obtain 16.71 MHz ±50 Hz at TP7 (R216).

4 WX 1 ~ 7 CH — Check if the DC Voltage on all channels is kept within

1.0 V to 4.0 V at TP4.

DC CORD

FUSE

ANT

J501

TP7

R216

TP3

R304

L301

TP4

R325

CT301

J502

WA901

GND(BLK)

13.8v(RED)

— 7 —

DC CORD

ANT

J501

L205

RT201

J502

Microphone jack J751

WA901

GND(BLK)

13.8v(RED)

FUSE

Transceiver

AF Oscillator

PTT

MIC

Jack

ANT

Jack

J501

J751

Dummy Load

(50-ohm)

And Attenuator

RF Power Meter Modulation Meter

10 F

16V

ALIGNMENT OF TRANSMITTER SECTION

Test Equipment Required and Connections

•DC power supply: 13.8 V •Modulation meter •AF oscillator

•RF power meter •Dummy load (50-ohm) & attenuator

Preset

•ALERT/WX/CB position: CB

Alignment Procedure

Alignment Point Locations (Main PCB)

Step Preset to Adjustment Remarks

1No modulation

19 CH L205 Adjust L205 by turning the core clockwise to obtain 3.8 W

reading on the RF power meter.

2 No modulation — Confirm frequencies of all channels are within specification.

3 No modulation RT201 Adjust RT201 to position the indicator in the meter MT501

just on "SIG9".

— 8 —

Transceiver

ANT

Jack

J501

EXT.

SP.

AC Voltmeter

SINAD Meter

Dummy Load

(8-ohm)

Distortion Meter

Signal Generator

ALIGNMENT OF RECEIVER SECTION

Test Equipment Required and Connections

•DC power supply: 13.8 V •AC voltmeter •Dummy load (8-ohm, 5 W resistive)

•Signal generator (SG) (27.205 MHz, 1 kHz, 30% AM modulation, output inpedance 50-ohm): CB

(162.45 MHz, 1 kHz, ±3kHz Dev. FM modulation, output impedance 50-ohm): WX

•SINAD Meter •Distortion meter

Preset

•ALERT/WX/CB: CB

Alignment Procedure

Step Preset to Adjustment Remarks

Vol.: Max.

SQ.: Min.

RX: 20 CH

L3, L1, L7, L5

L6, L2

Connect the SG to the antenna jack (J501) and the AC voltmeter

across the dummy load (8-ohm) to the external speaker jack (J3).

Adjust coil (L1 ~ L7) to obtain the maximum reading on the AC

voltmeter with keeping the level of the SG.

Vol.: Standard

SQ.: Min.

RX: 20 CH

Set the output level of SG to 1 mV (−47 dBm).

Adjust coil L4 to obtain minimum Reading on the Distortion

Meter.

Vol.: Standard

20CH

SQ.: Max.

RT1 Set the output level of SG to 1 mV (−47 dBm).

Adjust RT1 so SQ just opens.

Vol.: Standard

SQ.: Min.

RX: 20 CH

RT2

Set the output level of SG to 100 µV (−67 dBm).

Adjust RT2 to position the indicator in the meter MT501 just on

"SIG9".

5 WX: 3 CH L103 Set the output level of SG to 100 µV (−67 dBm) No modulation.

Adjust coil to obtain the maximum reading on the AC voltmeter.

6 WX: 3 CH RT101 Set the output level of SG to SINAD 15 dB.

Adjust RT101 so SQ just opens.

— 9 —

ANT

J501

DC JACK J502

GND(BLK)

13.8v(RED)

L7 L1 L3

L4 L103

RT2

RT1

RT101

DC CORD

FUSE

Alignment Point Locations (Main PCB)

— 10 —

Unit will not tum on

Check the voltage

of IC502.

Power ON NG

Check the power

SW VR601.

NG Replace IC502.

Is display normal?

Check the voltage

at IC502. Replace IC502.

Replace Fuse.

Check the

oscillation at pin

26 of IC401.

Check the

voltage at pin 25

of IC401.

Check the voltages

of IC403.

Replace IC403.

Check the

voltages of IC402

and Q401.

Replace IC402

and/or Q401.

Replace X401.

the voltages

of Q407, Q404

and Q405.

Replace Q407

and/or Q404, Q405.

Check

Check the

soldering of the cable

between MAIN and FRONT

PCBs.

Replace soldering.

Check the

voltage of D703. Replace D703.

Check the Fuse.

Check RX and TX

sections.

TROUBLESHOOTING

SYSTEM CONTROL SECTION CLOCK

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