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.
All Rights Reserved.
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
CH
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
CH
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
5
4
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.
J3
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
1
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.
2
Vol.: Standard
SQ.: Min.
RX: 20 CH
L4
Set the output level of SG to 1 mV (−47 dBm).
Adjust coil L4 to obtain minimum Reading on the Distortion
Meter.
3
Vol.: Standard
20CH
SQ.: Max.
RT1 Set the output level of SG to 1 mV (−47 dBm).
Adjust RT1 so SQ just opens.
4
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
J3
L5
L6
L2
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.
OK
OK
OK
Is display normal?
Check the voltage
at IC502. Replace IC502.
NG
Replace Fuse.
NG
OK
Check the
oscillation at pin
26 of IC401.
Check the
voltage at pin 25
of IC401.
Check the voltages
of IC403.
Replace IC403.
NG
OK
Check the
voltages of IC402
and Q401.
OK
Replace IC402
and/or Q401.
NG
Replace X401.
the voltages
of Q407, Q404
and Q405.
OK
Replace Q407
and/or Q404, Q405.
NG
Check
Check the
soldering of the cable
between MAIN and FRONT
PCBs.
Replace soldering.
NG
NG
NG
NG
NG
OK
OK
OK
Check the
voltage of D703. Replace D703.
NG
Check the Fuse.
OK
Check RX and TX
sections.
OK
OK
TROUBLESHOOTING
SYSTEM CONTROL SECTION CLOCK