Kenwood KRC-444D User manual

KRC-444D/L
KENWOOD
SERVICE MANUAL
©1986-7 PRINTED IN JAPAN
BS1-3008-00 (O) 1068
Knob (Button) Panel ass‘y * Knob (Button) Handle ass’y
(K27-1645-04) x2 {A20-) (K27-1651-04) (KO01-0078-03)
|
Knob (Button) | Knob (Button) | Knob (Button)
(K27-1364-04) (K27-1652-04) (K29-2582-04)
i | |
Knob (Button) | Knob (Button) | Knob (Button)
1
Knob
Knob
(Button)
|
|
(K29-0440
-03)
|
(K29-2415-04)
|
(K29-2445-04)
|
{K29-2416-04))
(K29-2442-04)
x6
!
|
|
Knob
(Button)
Knob
(Button)
_
Knob
(Button)
Knob
(Button)
(K29-2583-04) (K29-2443-04)
(K29-2444-04)
(IK29-2583-04)
x2
Metallic cabinet ass’y
{A01-1430-13)
Cord with connector
: (E30 -1497-05)
* Refer to parts list on page 27,
Photo is KRC-444D.

KRC-444D/L
DISASSEMBLY FOR REPAIR
. Remove three screws retaining the top cover (@).
. Remove the top cover in the directions of arrows C2) ).
. Remove five screws retaining the bottom cover (@).
. Remove the bottom cover in the directions of arrows
(@).
BWN-
5. Remove volume knob (@).
. Remove eject and FF. REW. knob (@).
7. Remove four screws retaining the handle with a hexagon
wrench ‘@ ).
8. Remove the front panel in the directions of arrows
(©).
oO
9. Remove two screws retaining the mechanism ass’y C9) ).
10. Extract the connectors (CN1, 5) of the synthesizer
unit (X14-1952-70) (QD).
11. Remove the mechanism ass‘y in the directions of
arrows ().

KRC-444D/L
DISASSEMBLY FOR REPAIR
12. Extract the connectors (CN2, 3) of the S.D.K. unit
(X13-5432-70), remove the synthesizer unit (X14
-1952-70) in the directions of arrows (® ).
13. Remove the grounding terminal of the synthesizer
unit (X14-1952-70) ( ®).
14. Extract the connectors (CN1, 4, 6) of the synthesizer
unit (X14-1952-70) (Q)).
15. Extract the flexible PC board from the connector
(CN7) of the synthesizer unit (X14-1952-70) in the
directions of arrows (® ).
16. Remove two screws the shassis ( @%).
17. Resolder the synthesizer unit (X14-1952-70) foil side
and shassis ( @ ).
18. Resolder the tuner unit (X05-3182-70) and_ shassis
(®).
19. Remove four screws retaining the front shassis (@).
20. Remove volume nut (@ ).
21. Remove four screws retaining the synthesizer unit
(X14-1952-70) ( @)).
22. Extract the synthesizer unit (X14-1952-70) of the
shassis in the directions of arrows (@® ).
REMOVING THE POWER IC (X14-1952-70) (1C4)
1. Remove twe screws retaining the shassis (@).
2. Remove |C4 from the synthesizer unit (X14-1952-70)
foil side (@).
3. Extract IC4 (X14-1952-70) in the directions of arrows
(©).

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KRC-444D/L
CIRCUIT DESCRIPTION
Description of Components
TUNER UNIT (X05-3182-70)
Component Use/Function Operation/condition/compatibility
FM IF Detection
Noise Canceller
MPX
LOCAL/DX SW
IF Gain
ANRC Buff.
CRSC Driver
S.D.K. UNIT (X13-5432-70)
Component Use/ Function Operation/condition/compatibility
1C1 ve TAPE EQ AMP
IC2 SK DECORDER
IC3 DK DECORDER
Qi METAL Select OFF when METAL mode.
Q2 DK AMP DK signal (125Hz) AMP.
Q3 DK AMP GAIN Select ON when DK mode (Amp gain of Q2 turns high.) 17mV—50mV (TP1)
04 Buffer Inverter ON when DK mode.
Q5 125Hz VCO STOP ON when SDK mode. (VCO stops when SDK is OFF.)
Signal (TAPE/RADIO) Select ON when TAPE mode. (OFF when a signal is interrupting.)
Signal (TAPE/RADIO) Select ON when DK mode.
SYNTHESIZER UNIT (X14-2952-70)
Operation/condition/compatibility
IC1 Controller
1C2,1C3
POWER AMP
ICS PRE-OUT AMP
Q1,Q2 9V AVR
FM Power supply Select
SDK Power supply Select
ON when FM/SDK mode.
ON when SDK mode.
Q6,Q7 AM (MW/LW) Power supply Select ON when AM (MW/LW) mode.
Q8,Q9 MW Power supply Select ON when MW mode.
Q11,Q12 Mute Drive ON when pu-processor Mute, Mech Mute mode.
Q13,014 TAPE Power supply select ON when tape is loading.
5V AVR
ACC OFF Mute Drive
Microprocessor CE SW
Buffer AMP
LOUD SW
LOUD SW
Q25 Muting
Q26 Muting
VOL UP
SK STOP
MONO SW
Q31 SD (Station Detector)
BAND Select SW
BAND Select SW
Mute SW
ST IND Prohibit Release
Q15
Q16
017,Q18
Q21 ,Q22
OFF when Acc signal is down.
ON when Power SW is ON (CE terminal turns Low to High.)
ON when LOUD SW is ON. (L ch)
ON when LOUD SW is ON. (R ch)
ON when Muting. (L ch)
ON when Muting. (R ch)
OFF when VOL UP mode.
ON when SK IND lit on.
ON when MONO SW is ON.
ON when SEEK STOP mode.
ON when Micro-processor BAND 1 terminal is ‘““H’’.
ON when Micro-processor BAND 2 terminal is ‘’H’’.
OFF when Micro-processor Mute signal is output.
ON when SDK mode.
Q39 BAND Key Prohibit SW ON when TAPE mode.
041 ,Q42 LPF (FM/MW)
043,044 LPF (LW)
ON when FM/MW mode. {OFF when LW mode.)
OFF when FM/MW mode. (ON when LW mode.)
ON when FM/MW mode. (OFF when LW mode.)
ON when AM (MW/LW) mode.
LPF SW
LPF SW
LPF SW
MONDO Display Prohibit
O46
Q47
048,049

KRC-444D/L
CIRCUIT DESCRIPTION
AND-GATE For CPU Key Matrix
Operation Description
A 1} B PIN 7 -—- GND (OV)
B
PIN
14
----
Vpp
(SV)
Vpp (5V)
* 2 on a
GND (OV)
Synthesizer Unit .-Com: u.PD 1708G
FUNCTION OUTLINE
Receiving frequency, Channel spacing, Reference frequency, Intermediate frequency
FM band
Frequency range Channel spacing
87.50~ 108.0 MHz * 50kHz
CPU Key Matrix Operation
The source clock from the CPU is input to A-input via the
AND-GATE at any time to apply the control signal to B-
input.
When the signal is input to B-input, the output Q goes
high and input as the CPU key input. When the B-input is
low level, output Q is always low. Output Q is synchro-
nized with input A.
Reference frequency Intermediate frequency
12.5 kHz 10,700
“MANUAL 25 kHz
AM band
Frequency range Channel spacing
Reference frequency Intermediate frequency
522~-1611 kHz 9 kHz
9 kHz 450 kHz
153 ~281 kHz " 9kHz
* MANUAL 1 kHz
Tuning Function
(1)
(2)
Auto Tuning (Sawtooth wave mode)
Seek Up: Once a station is tuned, it is held tuned.
Manual Tuning (Sawtooth wave mode)
Manual Up/Down: Frequency is advanced up or
down in steps by pressing the
push switch.
Pressing for a half second or
more advances it up or down
continuously until the switch is
released.
Preset Memory Recall
6 stations on each FM, MW. and LW band can be
preset independently with the 6 buttons. The last sta-
tion is stored in memory for each band when power is
turned off.
1 kHz 450 kHz
Tape Function
1) Tape running indicator
2) METAL control
Radio Function
1) MONO contro!
Other Functions
1) LOUDNESS control

KRC-444D/L
CIRCUIT DESCRIPTION
TERMINAL DESCRIPTION
Terminal Configuration (Top View)
aot [Jj 26
4c]
fT
CCt~—“‘CLSS
420 [ee DG:
43L Px)
440 sy)
450 uPD1708G-637-00 [2
46 CJ (TOP VIEW) [20
47 Pot—“;i‘*
480 TB
fo 17
p16
TS
P14
7 8 9
10 11 12 13
1
KS,
(PB,)
29
BANDZ/N.R
30
METAL-LOC
31 LOUDNESS
2
3
[Pin No.
este
p 2 |
| 3
a
is
20
ae
| 12 |
| 13 |
rie
ie
4
5
7
1
1
1
1
1
1
7
KS,/K, (PA,)
KS,/K, (PA,)
2
4
| 18 |
| 19
| 20 |
p24
| 23
KS, (PB,)
KS, (PB,)
* Not used.

Pin description
KRC-444D/L
CIRCUIT DESCRIPTION
Pin Name
Description
LCD segment signal
LCD segment signal output pin (1/2 duty, 1/2 bias LCD should be used. Frame
frequency: 100 Hz, Drive voltage: VDD)
LCD common signal
LCD common signal output pin
Power input
Device power supply pins
During device operation, 5 V + 10% voltage is supplied via these pins. Either of them
can be used for supplying the power individually. The rising time of VDD should be less
than 500 ms (0 to 4.5 V). When the rising time is too long, or when the VDD is not
lowered completely to O V and then raised to 4.5 V from the voltage lower than the
operating rate, the diode switch condition for initialization is not read out correctly. In
such cases, use the CE pin so that the diode switch status can be read out for
initialization.
FM VCO input
This pin inputs the FM station output signal.
Since it incorporates the AC amp, cut the DC signal with the capacitor.
AM VCO input
This pin inputs the AM station output signal.
Since it incorporates the AC amp, cut the DC signal with the capacitor.
Ground
Connect to the ground terminal of the set.
Error Out
Charge pump output of the phase detector consisting of PLL. When the frequency
divided by the oscillating frequency is higher than the reference frequency, these pins
output high level signals, and when it is lower than the reference frequency, they go
low. When the frequency (divided by the oscillating frequency) is coincided with the
reference frequency, it enters into the floating status.
AF MUTE
Chip Enable
Crystal resonator
This pin is used to input the selected signal from the device. When operating the-PLL
section, this pin goes high, and when the PLL section is stopped, it goes low. When at
low level, the display goes off. However, a low level signal below 134 ys or high level
signal is not accepted.
Connectors of the crystal resonator.
Connect the 4.5 MHz crystal resonator.
Mute Out
This pin outputs the muting signal to eliminate shock noise when the PLL is unlocked
and pop noise when switching between Tape and Radio, and is active low.
(CMOS output)
For timing details, refer to the AF Mute Out Timing Chart. When the CE pinis low, this
pin is active low.
Band Out
FM/MW switching output pin
FM: High
MW: Low
When the MODE switch is set to ‘1"’ (Tape mode), this pin is low.
When the SDK is provided, follow the SDK section.
Key return signal source and
Key return signal input
This becomes the source of key return signal to read out the diode matrix for
initialization only when the power is turned on for the first time (rising time of VDD) or
when the set is returned from the back-up condition (CE: Low to High).
Then, this inputs the key return signal for the key matrix. Insert the pull-down resistor.
(CMOS input /output)
Key return signal source and
Key return signal input
This becomes the source of the key return signal to read out the diode matrix for
initialization only when the power is turned on for the first time (VDD rising time) or
when returning from the back-up condition (CE goes high from low).
Then, this inputs the key return signal for the key matrix. Insert the pull-down resistor.
(CMOS input /output)
Key return signal input
This pin inputs the key return signal for the key matrix. Insert the pull-down resistor.
(CMOS input)
Key return signal source
This pin outputs the key return signal for the key matrix.
Since the synchronous current is greatly lowered because of its configuration, the
reverse-current prevention diode will be not necessary for the key source side.
(CMOS output)
METAL/DX/LOC LOC Out
{In radio mode: DX/Local On/Off output pin
When “LOC” is displayed on the LCD panel, high level signal is output. When it is not lit,
low level signal is output. (When the power is turned on, low level status is initialized.)
In tape mode: METAL On/Off output pin
When “METAL” is displayed on the LCD panel, low levet signal is output. When it is not
lit, high level signal is output. On initialization when the tape power is turned on, high
level is output.

KRC-444D/
CIRCUIT DESCRIPTION
Symbol Pin Name
Description
LOUDNESS output pin
When “LOUD” is displayed on the LCD panel, low level signal is output. When it is not
lit, high level signal is output.
When the power is turned on first (VDD rising time), low level signal is output.
LOUDNESS Loudness Out
(CMOS output)
DOLBY output pin
When “DOLBY” is displayed on the LCD panel, high level signal is output. When it is not
lit, low level signal is output.
On initialization when the power is turned on, low level is output.
BAND2/NR
When Band A is “0” or “1” and the NR selector is “1”, this
functions as the NR on/off output pin. When “NR” is dis-
played on the LCD panel, high level signal is output.
When it is not lit, low level signal is output.
This pin can be operated in the TAPE/RADIO mode.
On initialization when the power is turned on, this pin is at
low level.
When BAND A is “0”, “1” and the NR selector is “0”, this
function as the WIDE-ADV on/off output pin.
@ Inthe Radio mode:
This functions as the WIDE on/off output pin.
When “WIDE” is displayed on the LCD panel, high level
signal is output, and when it is not lit, low level is
output.
@ Inthe Tape mode:
This functions as the ADV on/off output pin.
When
“ADV"
is
displayed
on
the
LCD
panel,
high
level
signal is output, while it is not lit, low level is output.
On
initialization
when
the
power
is
turned
on
first,
it
is
at low level.
When BAND
A
is
“0”
and
the
NR
selector
is
0”
(SDK
oper-
ation
is
normal
only
when
in
this
status),
and
BAND
B
is
“1"" this pin functions as the BAND 2 output. BAND 2 be-
comes
the
band
switching
output
port
in
combination
with BAND 1.
Output

KRC-444D/L
CIRCUIT DESCRIPTION
1. KEY MATRIX CONFIGURATION
1-1. Key Matrix Layout
KSg (28)
KSg (25)
KS, (20)
REeaN oN Ree N
SK
The SS in the SSS shows the pin no.
SS
LL] : Momentary switch SS : Diode matrix (closed/opened by diode)
SS
P
YZ : Alternate switch or transistor switch | : Open
LLL
1-2. Switch Connection 1-3. Key Matrix Connection
Momentary switch Alternate switch
Kn
uPD1708G-637-00 KSo
a
KSm KSm
Diode matrix or open Transistor switch
Vop
KSm—
el
: Momentary switch
i
: Alternate switch or
transistor switch
: Diode matrix
tk}