Cobra 148GTL User Manual

R Jackson

Euro Radio Co

PC - 412

D D

ANL

NB/ANL

OFF

S405-1

NB/ANL SWITCH

VR4041KVR404

RF GAIN

C C

PC-426

TLR321D401 TLR321D401

B B

S403-3

S403-3 MODE

MODE

LSB AM USB

VR402

20K

VOICE LOCK

How to unlock the VOICE LOCK. 1 Remove D52 2 Remove R44 3 Remove R174 and solder a jumper in its place. 4 Unsolder the red wire that comes from the Voice Lock pot from the PCB and solder in to pin 1 IC4 MB3756.

J405

5 Change R175 to a 1K

ANT

A A

To improve noise blanker performance change the following components C1 from (33p) to (18p), C2, 3, 4, 7, and 13 from (2n2) to (10n), C6 from (2n2) to (4n7), R1 from (3K3) to (10K) R2 from (18K) to (33K), R4 from (470R) to (680R), D1 and 2 from (1N60) to (1N6263).

330RR3330R

TR1

2SC1675

18KR218K

470RR4470R

33pC133p

3K3R13K3

C2 2n2C22n2

C4 2n2C42n2

C3 2n2C32n2

LA038L1LA038

100pFC5100pF

2SC1675

22ORR522OR

8.0 VOLTS WITH (N.B) SWITCH ON

R6 47KR647K

TR2

TR3

2SC1730

R7 2K7R72K7

C6 2n2C62n2

NOISE BLANKER

150RR8150R

R9 68RR968R

C81nC8

TR4

2SC945

TR5

2SC945

LA179L2LA179

C7 2n2C72n2

2SC945

R11

TP6TP6

R10

10K

1N60D21N60

1N60D11N60

82pC982p

10K

100K

R12

R12 10K

10K

C10

0.22u

To improve the receiver bandwidth and signal to noise change the following components C41, 47 from (2p) to (3p), TR14 from (2SC1674) to (2SC2999), D21, 22 from (1N60) to (1N6263),

D68

R43

R43 IS1588

IS1588

150R

AGC LINE

TR14

L4 C30

C30 4n7

4n7

D13

C34

MC301

4n7

C31

C31 12p

12p

D12

MC301

D16

IS1588

R46

R46 4K7

4K7

D14

C331uC33

IS1588

C32

4n7

TX + 8.0 vdc

R94

R47

680R

3K9

RX + 8.0 vdc

R45

R241

1K5

100R

PC-416

ALL RESISTORS 680R

S401 CHANNEL SWITCH

TR28

2SC945

R1731KR173 1K

R1371KR137

13.8 VDC

R44

R44 8K2

8K2

R174

12K

R175

3K3

R176

R176 330R

330R

D73

1N60

D45

D45 1N60

1N60

C138

4n7

LA261L4LA261

D15

IS1588

R481KR48 1K

C201

10n

CC1 HA003

R177

R177 470R

470R

D74

D74 1N60

1N60

C140

4n7

C202

10n

C351nC35 1n

R256

R256 560R

560R

C225

C225 4n7

4n7

D46

D46 1N60

1N60

S/RF

CAL SWR

ALWAYS 8.00 VOLTS

C139

0.5p

2SC1674

RX RF AMP

R50

R50 2K2

2K2

R491KR49 1K

C384pC38

C371nC37

PLL PIN VOLTAGES PIN 1 = 3.4 VDC PIN 2 = 4.28 VDC

PIN 3 = 5.16 VDC PIN 4 = 3.45 VDC PIN 5 = 3.45 VDC PIN 6 = 8.0 VDC PIN 7 = 4.22 VDC PIN 8 = 4.46 VDC PIN 9 = 8.0 VDC PIN 10 = NC PIN 11 to 16 CH SWITCHED 8.0 VDC PIN 17 = 3.66 VDC PIN 18 = GROUND All voltages ± 3%

R95

R95 1K5

1K5

IC1

MB8719

AO2

GND

AI2

FIN

AO1

AI1

VCC9**

C84

C82

1000u

47n

C141

C142

68p

27p

L36

L36 LE051

LE051

VR4065KVR406

CAL SET

S408-1

SWR S/RF

SWITCH

R51

R51 100R

100R

R96

R96 33K

33K

R97

R97 2K2

2K2

D31

IS1588

R163

R163 22K

22K

L35

LE051

R178

R178 10K

10K

1/2 WATT

C412pC41

LA259L6LA259

LA260L5LA260

27 MHz

C421nC42 1n

C391nC39

R52

100R

C401nC40 1n

C87

C87 2n2

2n2

R207

R207 2K7

2K7

C79

TP9TP9

10n

10n R98

R98 12K

12K

R99

TP10TP10

33K

R100

6K8

C88

R101

47p

10K

C81

L17

2u2

470u

C80

C80 2u2

2u2

10.240 MhzX210.240 Mhz

C85

C86

C91

18p

4n7

10p

LSB = 33.9765 MHz AM = 33.975 MHz USB = 33.9735 MHz

L21

LA256

R1381KR138

C111

C111 10n

10n

L37

LE051

D47

IS1588

C143

180p

C1441uC144

VR6

100K

RF METER PRE-SET

S/RF

CAL

SWR

S408-2

SWR S/RF

SWITCH

2SC1675

1st RX MIXER

R53

R53 10K

10K

L51L51

L16

L16 100u

100u

R1041KR104

TR29 B = 1.46 VDC E = 1.08 VDC C = 8.10 VDC All voltages ± 2%

2SC1675

TRIPLER

R139

R139 100R

100R

C112

C112 10n

10n

C1541pC154

D48

IS1588

C146

C146 390p

390p

M401

S/RF/SWR METER

TR15

C431nC43

R55

R55 R54

R54

100R

100R 180K

180K

L52L52

C89

C89 47p

47p

C90

0.47u

TR29

R1401KR140

L38

LC019

C147

C147 47p

47p

LA258L7LA258

C472pC47

7.8 MHz

C45

C441nC44

100p

TR20

2SC1675

LOOP MIXER

R103

R102

2K2

R141

R142

C113

2K2

10K

10n

C150

C150 330p

330p

L39

L39 LD098

LD098

C149

C148

C148 100n

100n

120p

LINKLINK

TR6

2SC945

R13

R13 470K

470K

C111nC11

LA257L8LA257

7.8 MHz

VCO MODULA PIN VOLTAGES PIN 1 = 7.8 VDC

PIN 2, 3, 4, AND 7 PIN 5 = 3.4 VDC PIN 6 = 0 VDC PIN 8 = 8.00 VDC PIN 9 = 7.3 VDC PIN 10 = 4.02 VDC All voltages ± 3%

IC2

UHIC 007

VCO MODULA

C92

C92 4u7

4u7

2SC1675

C1162pC116 2p

R143

R143 220R

220R

LSB AM USB

TR36

2SC1969

FINAL

MV13YH

LP2

LP2 LAMP

LAMP

2SA733

C485pC48

712

TR30 B = 3.80 VDC E = 3.20 VDC C = 7.90 VDC All voltages ± 2%

LOOP OSCILLATOR

TR30

R1441KR144

C114

10n

D49

R179

R179 100R

100R

R169

R169 47R

47R

1/2 WATT

R418

R418 100R

100R

1/2 WATT BRIGHT

DIM

AM IF STRIP

FET 3

FET 3 2SK19

2SK19

R561KR56 1K

TP1TP1

R107

R107 100R

100R

D33

IS1588

D34

IS1588

D32

IS1588

R187

R187 2K7

2K7

L41

C1911uC191

R1 3K3R13K3

2nd RX OSCILLATOR

7.3450 MHzX17.3450 MHz

R18

R18 5K6

5K6

D19

IS1588

D18

D18 IS1588

IS1588

R257

R58

680R

3K3

C50

C50 R57

R57

2n2

2n2 470R

470R

C49

C49 2n2

2n2

D17

IS1588

L57

470u

TX + 8.0 vdc

34.765 MHz = Channel 1

35.205 MHz = Channel 40

L25

L25 220u

220u

L26

L26 220u

220u

L24

220u

C229 2n2C229 2n2

C228 2n2C228 2n2

C227 2n2C227 2n2 R237

D75

D52

KB262

VR53KVR5 3K

TX FREQUENCY PRE-SET

TR38

2SC2166

DRIVER

D50

D50 C156

C156

MV1Y

MV1Y 220p

220p

R187

R187 330R

330R

C1 10pC110p

SVC251D1SVC251

C2 56pC256p

TR9

2SC1675

C17

C141nC14

100p

R201KR20

R19

C15

10K

100p

R21

R21 C16

C16

100R

2n2

FL3

FL067

C51

C51 2n2

2n2

R253

R591KR59

1K5

L11L11

C204

C204 2n2

2n2

11.325 MhzX311.325 Mhz

C119

10n

C120

10n

L27

L27 D35

D35

470u

IS2687

R239

R239 10K

10K

R149

R149 18K

18K

C106

R238

0.47u

10K

C215

R237

2n2

10K

R188

100R

L44

LD096

L43

C157

4n7

LD087

C158

C226

VR9

4n7

100p

500R

BIAS

VCO MODULA UHIC007

6K8R26K8

100RR5100R

C3 1nC3 1n

1N4148D21N4148

TR1

2SC1675

R3 5K6R35K6

320pC4320p

5K6R45K6 C5 120pC5120p

TR7

C13

C13 2n2

2n2

TR8

2SC945

R16

R15

10K

330R

R17

R17 3K3

3K3

C12

C12 100p

100p

LA268L9LA268

7.8 MHz

689

L19

LA216

C93

10n

R203

10K

C117

470p

R145

10K

R181

R181 10R

10R

C151

C151 4n7

4n7

D76

VR85KVR8

IS1588

BIAS

C153

47u

S406

DIMMER

SWITCH

L10

FL2

LA269

FL046

7.8 MHz

R106

R106 100R

100R

L20

LA195

34 MHz

R105

R105 100R

100R

C94

4n7

L59

LA284

USB

R236

R236 8K2

8K2 L23

L23

LA285

R148

R148 8K2

8K2 L22

L22

LA051

LSB

C118

R147

10n

8K2

L58

L58 470u

470u

C212

C212 470p

470p

R1461KR146

C213

L60

18p

470u

D69

IS2687

D51

IS1588

C152

L40

470p

LD101

LD087

TR37

L42

2SC496

LD098

BIAS REG

C154

C155

47n

100n

LINKLINK

R180

R180 270R

270R

1/2 WATT

1010

R22

R22 10K

10K

2nd MIXER

R62

R62 22R

22R

C52

C52 2n2

2n2 R61

R61

150R

R60

R60 220R

220R C53

C53 2n2

2n2

FET 1

FET 1 3SK45

3SK45

R241KR24 1K

7.8 MHz IF INPUT

D20

IS1588

C54

C54 2n2

2n2

R63

R63 68R

68R

C203

33p

R183

C159

12R

4n7

1N4148D31N4148

C61nC6 1n

LA163L3LA163

R25

C19

220R

4n7

C55

C55 2n2

2n2

R64

R64 1K5

1K5

R150

R150 220R

220R

D38

IS1588

D36

IS1588

Euro Radio Co

TR39

2SC2314

BUFFER

R184

C160

330R

4n7

TR2

R8 2SC1675

2SC1675

10KR810K

C81nC8

C75pC7 5p

R7 8K2R78K2

R6 5K6R65K6

FL1

FL040

455 KHz

R26

R27

1K5

1K8

R28

R28 3K3

3K3

IS1588D3IS1588

C22

R29

R29 2n2

2n2

220R

C21

C21 2n2

2n2

TR16 B = 1.02 VDC E = 0.50 VDC C = 8.40 VDC All voltages ± 2%

TR16

2SC1675

R68

R68 3R3

3R3

R67

R67 470R

470R

220R

AGC LINE

TR17 B = 0.70 VDC

L12

E = 0.00 VDC

LA270

C = 2.95 VDC All voltages ± 2%

C58

C58 2n2

2n2

TR17

2SC1675

R69

R69 3R3

3R3

2SC1675

L13

R73

LA272

33K

C56

C56 47n

47n

33K

R70

R70 3R3

3R3

C59

C59 47n

47n

C20

C20 47n

47n

R66

R66 15K

15K

R65

R65 10K

10K

Euro Radio Co

R108

C95

100R

47u

IC3

BALANCE MODULATOR

AN612

C98

C98 10p

C97

C97 10n

10n

TR31

TR31 2SC945

2SC945

AM SWITCH

R152

R152 10K

10K

D37

R186

R186 100R

100R

R185

R185 1K5

1K5

220RR9220R

10p

R205

R205 1K2

1K2

R110

BALANCE MOD

150K

PRE-SET

C96

C207

10n

47p

R109

R109 3K9

3K9

ALWAYS 8.00 VOLTS

CARRIER OSCILLATOR

R151

R151 22K

22K

TR32

7.8000 MhzX47.8000 Mhz 2SC1675

2SC1675

TPPTPP

C123

AM 7.8000 MHz

220p

LSB 7.7985 MHz USB 7.8015 MHz

C122

C124

R1531KR153

R154

100p

2n2

10K

7.8000 MHz IN AM MODE PLUS OFFSETS IN SSB

L46

LA220

C1632pC163

C162

C162 47p

47p

L45

LA254

C164

C164 10n

C161

C161 330p

330p

10n

NOTE:

If you find any errors or omissions, please let know the value of the component and or circuit reference. Please E-Mail me and I will correct them.

R416

R416 6K8

6K8

VR401

VR401 100K

100K

SQUELCH

R234

TR13

R33

R33 3K3

3K3

TR10

2SC945

FET 2

FET 2 2SK19

2SK19

R34

R32

R31

R30

3K3

330R

1K2

8.0 VDC IN AM MODE

TR18 B = 2.32 VDC

L15

E = 1.60 VDC

LA264

C = 8.00 VDC

R74

All voltages ± 2%

1K5

TR52

2SC945

R2221KR222

C59

C59 2n2

2n2

L14

LA271

TR18

2SC1730

R75

R76

C60

C60 47n

47n

C68

C68 15p

15p

VR4

VR4 10K

10K

R111

R111 560R

560R

R158

R158 3K9

3K9

C1255pC125

C199

C199 10n

10n

101112

R189

R189 100R

100R

C165

C165 4n7

4n7

150R

R206

R206 270K

270K

R113

R113 10K

10K

R112

R112 1K5

1K5

6.8 VDC IN AM MODE

C126

C126 10n

10n

C61

68R

2n2

C99

C99 2u2

2u2

TR21

2SC945

AM AUDIO SWITCH

R114

R1151KR115

27K

C46

2n2

AM TX AUDIO LINE

D39

IS1588

R155

R155 56K

56K

USB

CT2

CT2 20p

20p

L28

C127

470u

82p

34.765 MHz = Channel 1

D53

IS1588

35.205 MHz = Channel 40 PLUS OFFSETS IN SSB

L48

L48 LA219

LA219

9 7 6 8 14

IC5

SO42P

TX MIXER

TX + 8.0 vdc

13.8 VDC13.8 VDC

IS1588D8IS1588

C24

4u7

IS1588D5IS1588

R35

C23

0.47u

R331KR33 1K

R34

R34 3K3

3K3

C621uC62 1u

R116

R116 3K3

3K3

D40

IS1588

LSB

LA266

L29

L29 470u

470u

R191

R191 1K5

1K5

L47

L47 LA160

LA160

R35 180K

180K

IS1588D7IS1588

IS1588D6IS1588

C25

0.47u

TO S METER

C64

D22

220p

1N60

D21

D21 1N60

1N60

R79

R79 100K

100K

D24

IS1588

R78

R78 10K

10K

TR22

2SC945

C101

R118

R119

R117

47K

10K

470R

C100

C100 22u

22u

D41

IS1588

L30

L31

R156

LA265

22K

L32

470u

C128

27p

C129

C129 10n

10n

13.8 VDC

S403-2

S403-2 MODE

MODE

LSB

USB

TR11

2SC1675

IS1588D9IS1588

D10

IS1588

C26

C26 39p

39p

R361KR36 1K

R801MR80

R81

R81 68K

68K

C701nC70 R82

R82

1n 100K

100K

C655pC65 5p

C671uC67 C66

C66

1u 220p

220p

0.1u

R122

R120

15R

5K6

C103

C103 10u

10u

RX + 8.0 vdc

TR33

2SC945

R224

R224 3K3

3K3

R223

R157

10K

R166

R166 3K3

3K3

TR41

2SC1419

R193

R193 220R

220R

1 WATT

5.60 VDC IN AM MODE

13.75 VDC IN SSB MODE

NOTES There are small 10-volt electrolytic caps dotted all over the various 8V supply rails, change them to 16-volt types for better reliable. Known faults

-------------------Warble on SSB, and the PLL chip running hot. Check Pin 9 the PLL it should be at 8V but you will probably find it at 10 to 11 volts in which case change IC 4 (MB3756)

Warble on SSB. Check Pin 9 the PLL it should be at 8V if the voltage is bit low check C84 know to go low. Warble on SSB and low power. Check TR37 (2SC496) Bias regulator know to go o/c. Drift off frequency after warm-up. Replace C212 and C213 with 1% caps.

C29

R232

R232 2u2

2u2

1K5

R371KR37 1K

R381KR38 1K

D71

D71 1N60

1N60 C27

C27

D70

2n2

IS1588

C78

C78 10n

10n

R871KR87

D65

R86

IS1588

IS1588 47K

47K

D23

IS1588

R83

R83 100K

100K

R85

C711nC71

560K

TP3TP3

R89

R84

C69

10K

68K

68K 2n2

2n2

TP4TP4

R124

R124 10K

10K

C104

0.47u

TR23

2SC945

C2081nC208

C102

C102 4n7

4n7

R125

R123

56K

10K

C105

10n

R1211KR121

8.0 VDC IN AM MODE

10K

L33

C1301pC130

C131

100u

10p

R1951KR195

D45

D45 1N60

1N60

TR42

2SC945

R1941KR194

R228

D63

560R

IS1588

C173

10u

R88

R88 3K3

3K3

TR19

2SC945

R911KR91 1K

R126

R126 10K

10K

TR24

2SC945

2SA733

TR34

2SC1675

SSB ALC

VR11

C132

10K

4n7

SSB ALC PRE-SET

R225

R225 100K

100K

C1741uC174

VR105KVR10

AM POWER

R196

R196 4K7

4K7

ADJUST VR10 IN AM MODE FOR

5.60 VDC AT THE EMITTER OF TR41.

TR25

C107

R159

10n

18K

C75

C75 47n

47n

TR47

TR47 2SA733

2SA733

C72

C72 33u

33u

C74

C74 47u

47u

C108

0.47u

D59

IS1588

On some early models C18 is 47u change to 330u at 16 volt

C18

C18 47u

47u

R161

R161 10K

10K

IS1588

R160

8K2

TX + 8.0 vdc

TR12

TR12 2SC945

2SC945

R41

R41 2K2

2K2

VR31KVR3 R40

R40

1K 5K6

5K6

SQUELCH PRE-SET

TR19 B = 1.30 VDC E = 0.70 VDC C = 5.60 VDC All voltages ± 2%

R901KR90

R91

2K7

C73

C73 22u

22u

MIKE AUDIO

D60

IS1588

R128

15K

R129

33K

R1271MR127

C109

10u

D42

LOCK DETECTOR LINE (HI = LOCKED, LOW = UNLOCKED)

C230

0.47u

0.47u TR53

TR53

2SC945

R226

47K

C175

C175 470u

470u

R2081RR208 1R

C177

C177 100n

100n

TR13

2SA733

R421KR42 1K

D11

IS1588

D501 and VR501 Not fitted on early models

TR26

2SC945

D501

AMC

IS1588

R131

R130

10K

1K5

MB3756 PIN OUT PIN 1 = ALWAYS 8.0 vdc 100mA

PIN 2 = SUPPLY 13.8 vdc PIN 3 = VREF 8.0 VDC 100 mA PIN 4 = GROUND PIN 5 = RX/TX CONTROL PIN 6 = RX 8.0 vdc 100 mA PIN 7 = NC PIN 8 = TX 8.0 vdc 200 mA All voltages ± 3%

VOLTAGE REGULATOR WITH RX/TX CONTROL

IC4

MB3756

37124

C133

C134

10u

ALWAYS 8.00 VOLTSALWAYS 8.00 VOLTS

13.8 VDC

On early models C181 is 10u I change this to 1000u at 16 volt.

R2581MR258

C181 1000uC181 1000u

C232 2u2C232 2u2

C176

IC6

47u

AF AMP

TA7222AP

R197

2 345

3K3

R198

C1781nC178

68R

C180

C179

4u7

22u

150K

D67

IS1588

D66

IS1588

R235

R235 15K

15K

R132

R132 10K

10K

VR5011KVR501

AM AMC

C136

47n

89 7

TR48

2SA733

VR15KVR1 5K

AM S/METER PRE-SET

RX + 8.0 vdc

R133

R133 47K

47K

TR27

2SA733

PA AUDIO SWITCH

C110

10n

AM AUDIO IN CB MODE PA AUDIO IN PA MODE

TR35

2SC945

R162

3K3

D44

R164

1N4003

560R

D43

IS1588

C135

0.47u

NOTE:

Filter cap C181 can be any size from 100u to 2200u at 16 volt it all comes down to what you can physically mount on the PCB. The higher the capacitance the better the filtering.

C183

C183 100n

100n

C182

R227

22n

3K9

R134

3K3

IS1588

13.8 VDC

AF BUFFER

VR25KVR2

SSB S/METER PRE-SET

D61

TF147T1TF147

C172

C172 1000u

1000u

R201

R201 3K3

3K3

R202

R202 22K

22K

TR45

2SC458

R200

R199

6K8

680R

USB

S403-1

MODE

LSB

ANL

OFF

NB/ANL

S405-2

NB/ANL SWITCH

LOW HI

S407

C77

R93

100n

22K

C76

C76 47n

47n

R165

R165 1K5

1K5

C188

D55

1N4003

47n

L49

LD077

C1701nC170

C171

C171 4n7

4n7

C166

C166 4n7

4n7

C167

4n7

C168

4n7

C169

4n7

C187

C187 100n

100n

C186

C186 220u

220u

C1851nC185

S407 TONE

TONE

VR403

10K

VOLUME

VR4051KVR405

DYANMIKE

J404

J404 L404

L404

MIKE SOCKET

1u8

AUDIO

1234

RXGND

C4071nC407

C4051nC405

S404-1

S404-1 CB/PA

CB/PA

S402

ON/OFF

LD013

Size Document Number Rev

Cobra 148 GTL.SCH PCB Number PC - 412

Date: Sheet of

Date: Sheet

L401

C140

22n

L402

C403

C4021nC402

10n

S404-2

S404-2 CB/PA

CB/PA

C4031nC403

J403

DC 13.8 VOLTS

J401PAJ401 PA

J402

EXT SPEAKER

RX LINE

SPEAKER

11Tuesday, January 22, 2008

SP401

1.2