Kenwood KRC-279RA User manual

CASSETTE RECEIVER
KRC-15RG
SERVICE MANUAL © 2000-10 PRINTED IN KOREA
B51-7684-00 (K) 2161
KRC-179RA/RG/RYA/RYG
KRC-25RA/RG
ANTENNA ADAPTOR
(T90-0523-05)
(Except KRC-281RG)
KRC-279RA/RG/RYA/RYG
KRC-281RG
KRC-279R
CD/MD-CHANGER CONTROL
KRC-25R
CD/MD-CHANGER CONTROL
KRC-15R KRC-179R
KRC-281R
CD/MD-CHANGER CONTROL
KRC-15RG (E) KRC-179RA/RG/RYA/RYG (E)
KRC-25RA/RG (E)
PLASTIC CABINET ASSY
(A02-1486-13)
LEVER
(D10-3031-04) x2
MOUNTING HARDWARE ASSY
(J21-9491-13)
DC CORD
(E30-xxxx-xx)
(Refer to the parts list.)
STAY
(J54-0606-04)
SCREW SET
(N99-1610-15)
(KRC-281RG only)
SCREW SET
(N99-1632-05)
(KRC-281RG only)
AUD
123456
CLK
ATT
SRC
PWR
OFF
SCAN RDM REP T.C/D.SCN M.RDM
LOUD
DISC
HIGH POWER
40Wx40Wx 4
MENU
FM
AM
FF REW
PR OG
VOL ADJ NAME SETTI
PTY
AUD
123456
CLK
ATT
SRC
PWR
OFF
SCAN RDM REP T.C/D.SCN M.RDM
LOUD
DISC
HIGH POWER
40Wx40Wx 4
MENU
FM
AM
FF REW
PR OG
VOL ADJ NAME SETTI
PTY
AUD
123456
CLK
ATT
SRC
PWR
OFF
SCAN RDM REP T.C/D.SCN M.RDM
LOUD
DISC
HIGH POWER
40Wx40Wx 4
MENU
FM
AM
FF REW
PR OG
VOL ADJ NAME SETTI
PTY
AUD
123456
CLK
ATT
SRC
PWR
OFF
T.CALL
LOUD
HIGH POWER
40Wx40Wx 4
MENU
FM
AM
FF REW
PR OG
VOL ADJTI
PTY
AUD
123456
CLK
ATT
SRC
PWR
OFF
T.C/ALL
LOUD
HIGH POWER
40Wx40Wx 4
MENU
FM
AM
FF REW
PR OG
VOL ADJTI
PTY
KRC-279RA/RG/RYA/RYG (E)
KRC-281RG (M)
(KRC-281RG only)
40%

KRC-15R,179R,25R,279R,281R
2
CONTENTS / BLOCK DIAGRAM
CONTENTS / BLOCK DIAGRAM...............................2
COMPONENT DESCRIPTION...................................3
MICROCOMPUTER'S TERMINAL DESCRIPTION ...4
TEST MODE...............................................................6
ADJUSTMENT............................................................7
PARTS DESCRIPTIONS............................................8
PC BOARD.................................................................9
SCHEMATIC DIAGRAM...........................................13
EXPLODED VIEW....................................................18
PARTS LIST .............................................................21
SPECIFICATIONS......................................Back cover
CONTENTS
BLOCK DIAGRAM
IC1
KEY
PAN 5V
MUTE
B.U. DET. B.U.
ACC
P-CONT.
MUTE PRE
POWER IC
EQ. AMP.
CH ISO AMP NC/MPX/ E-VOL.
CD/MD CHANGER
FRONT Lch
FRONT Rch
REAR Lch
REAR Rch
J2
LCD DRIVER
LCD
ME1
MAIN
CASSETTE MECHA.
IC5
1 Lch 2 Rch PRE OUT
IC2
IC4
IC3
SP OUT
REAR
J4
PAN IN SW
ACC DET.
P-CONT.
J2
J5
IC1
FRONT-END
J1
FM+B
Q201
AM+B
Q203
AM BPF
FM BPF
C154,R206 C153,R207
Q320
Q450,451
Q49 Q50 Q350,351,370
Q53
SW 5V
Q54-57
8V
Q58-61
ILLUMI. B.U. 5V
Q51,52
SYSTEM u-COM
S1
S2 S3
RST SW
Q301
D1-15
PL1,2
ANT.
TEL MUTE
DECODER RDS
IC7
Q501,502
MP SW
40W
RST IC
RST
IC6
ED1
FM ANT AM ANT
RF GND
FM+B AM+B
OSC GND OSC GND OSC GND
VT
PLL +B
IFC OUT
SDA
SCL
DIG GND
IF1+B
IF1 GND
S-METER
IF2 GND
SD
FM+B
P.ON
ACC DET
B.U. DET
SCL
MUTE
SDA
P CON
PANEL
RESET
L CLK
L DATA S
L DATA L
FWD/REV
MOTOR
CH CON
DATA H
DATA C
REQ H
REQ C
CH CLK
Rch COM Lch
MP IN AM MPX
OUT RR
OUT LR
OUT RF
Rch
LEVEL SCL SDA
OUT LF
Rch
STBY MUTE
Rch Lch
T-MUTE
FWD
REV
B.U.5V
8V
B.U.
CH RST
S MUTE
8
5
10
B.U.5V
AM+B
VDD 5V
PACK IN
L RES
PHONE
CH MUTE
BEEP
SVR
AMP. STBY
SVR AC GND (BEEP)
Lch Lch
Rch
Lch
1200mV
TAPE :1681mV CD/MD-CH :3529mV AM :772mV FM :1339mV
8V
RF GND
OSC GND
IF2 +B
AUDIO OUT
8V
S-METER SD PLL-SCL PLL-SDA
M1
HD1
L/R
55.6mV
B.U.5V
SW5V
8V
B.U.5V
AM: 170mV FM: 213mV
TAPE
PACK IN
(FF/REW)
AMP. MUTE
FF/REW
B.U.5V
R QUAL R CLK R DATA
SW5V
MP OUT QUAL
AFC
NOISE
B.U.5V
ILLUMI.
L CE
(X13)
M
KRC-15R,179R,25R,279R,281R (E,M)
A1
TEL DET
D380
5V
R205

3
KRC-15R,179R,25R,279R,281R
COMPONENT DESCRIPTION
REF No. FUNCTION OPERATION
IC1 SYSTEM µ-COM Controls the unit.
IC2 E-VOLUME Controls the volume and selects source.
IC3 MUTE LOGIC Controls the mute output.
IC4 POWER AMPLIFIER For the speaker output.
IC5 EQUALIZER AMPLIFIER For the cassette tape's signal.
IC6 RESET Resets the power.
IC7 RDS DECODER Decodes the radio data.
Q49 ACC DETECTION SW Outputs "H" during the ACC off.
Q50 BACK-UP DETECTION SW Outputs "H" when the back-up voltage is under 9.2V.
Q51,52 BACK-UP 5V DRIVER Works when back-up current exists.
Q53 P.ON 5V SW Works during the power on.
Q54,55 8V SW Works during the power on.
Q56,57 8V DRIVER Works during the power on.
Q58,59 ILLUMI +B SW Works during the power on.
Q60,61 ILLUMI +B DRIVER Works during the power on.
Q150 E-VOL MUTE SW Works when the back-up current is detected
or the changer mute works or system µ-com mute works.
Q151 SVR FORCED DISCHARGE SW Works when the amplifier mute works.
Q153 PRE OUT MUTE SW Works when the back-up current is detected
or the changer mute works or system µ-com mute works.
Q201 FM +B SW Works during FM mode.
Q203 AM +B SW Works during AM mode.
Q260 MOTOR +B SW Works during the tape mode.
Q261 MOTOR +B DRIVER Works when Q206 works.
Q301 CD-CH RESET SW Works when the power is reset and the reset SW works.
Q320 PANEL 5V SW Works when the back-up current exists and the panel
is attached on the unit.
Q350 P.CON DRIVER SW Does not work during the power off and the ALL OFF.
Q351 P.CON PROTECTION SW Works when the P.CON is short-circuited on the GND.
Q352 P.CON PROTECTION INHIBIT SW Inhibits the protection SW in a moment during the P.CON on.
Q353 P.CON DRIVER SW Does not work during the power off and the ALL OFF.
Q450,451 PRE OUT MUTE SW Works when the back-up current is detected
or the changer mute works or system µ-com mute works.
Q500 AUDIO OUTPUT BUFFER For RDS decoder.
Q501,502 AFC TIME CONSTANT SW Works during receiving FM signal.
Q503 NOISE BUFFER For noise level detection.
SYNTHESIZER UNIT (X14-656x-xx)

KRC-15R,179R,25R,279R,281R
4
MICROCOMPUTER'S TERMINAL DESCRIPTION
PORT No. PORT NAME I/O FUNCTION OPERATING CONDITION
1 PANEL I Panel detection. "L" : Panel exists.
2 L CE O LCD driver chip enable. -
3 L RES O LCD driver reset. -
4 AVSS - GND. -
5 R DATA I RDS data. -
6 R QUAL I RDS receiving. -
7 AVREF 1 - Reference voltage. -
8 IC2 SEL 1 I Selector. "L" : Normally.
9 IC2 SEL 0 I Selector. "L" : Normally.
10 - - - -
11 L DATA L I LCD driver communication data. -
12 L DATA S O LCD driver communication data. -
13 L CLK O LCD driver communication clock. -
14,15 - - - -
16 DATA C I Changer communication data. -
17 DATA H O Changer communication data. -
18 CH CLK I Changer communication clock. -
19-26 - - - -
27 MOTOR O Cassette tape motor SW. -
28 FF/REW I Cassette tape FF/REW detection. "L" : FF or REW works.
29-31 - - - -
32 SD I Signal detection. "H" : Signal exists.
"L" : Signal does not exist.
33 VSS 1 - GND. -
34 - - - -
35 PLL CLK O Front-end communication clock. -
36 PLL DATA I/O Front-end communication data. -
37 AM +B O AM power supply SW. -
38 FM +B O FM power supply SW. -
39 IC2 DATA I/O E-volume communication data. -
40 IC2 CLK O E-volume communication clock. -
(X14-) IC1 : µ-COM

KRC-15R,179R,25R,279R,281R
5
MICROCOMPUTER'S TERMINAL DESCRIPTION
PORT No. PORT NAME I/O FUNCTION OPERATING CONDITION
41 AFC O FM noise detection / Time constant SW. -
42 MUTE O Mute control. -
43 AMP MUTE O Power amplifier mute. -
44 - - - -
45 CH CNT O Changer control. -
46 REQ H O Changer request. -
47 - - - -
48 SVR O SVR control. -
49 AMP STBY O Power amplifier stand-by. -
50 BEEP O Buzzer signal output. -
51,52 - - - -
53 P.CONT O Power control SW. -
54 ACC DET I ACC detection. -
55 B.U. DET I Back-up detection. -
56 P.ON O Power SW. -
57 ILLUMI O Illumination SW. -
58 FWD/REV I Cassette mechanism FWD/REV detection. -
59 - - - -
60 RESET I System reset signal input. -
61 SEL 1 I Destination SW. -
62 R CLK I RDS clock. -
63 REQ C I Changer request. -
64 PACK IN I Cassette tape pack-in detection. -
65 KEY-REQ I Key signal input detection. -
66 SEL 0 I Destination SW. -
67 VSS 0 - GND. -
68 VDD 1 - 5V power supply. -
69 X2 - Main system clock. -
70 X1 I Main system clock. -
71 IC - GND. -
72 - - - -
73 XT1 - 5V power supply. -
74 VDD 0 - 5V power supply. -
75 AVREF 0 I A/D converter reference voltage. -
76 S METER I S-meter detection. "H" : S-meter exists.
"L" : S-meter does not exist.
77 PHONE I - Navigation mute : 2.5V or more.
Telephone mute : 1V or less.
78 NOISE I FM noise detection. -
79 AV CONT O A/D converter reference voltage. -
80 - - - -
(X14-) IC1 : µ-COM