JVC KD-A66 User manual

MODEL
KD-A66 A/B/C/E/J/U
STEREO
CASSETTE
DECK
No. 4193
June 1980

No. 4193
KD-A66A/B/C/E/J/U |
Contents
Page
Specifications... 0... ee es 2
FOQtUFOS ape cnt id ean erate bos ah A a ei ee ea ea ee 3
Controls and Connections... ......-----00 ee ee eee 3
Main Parts Location... ...... 2.002: eee ee eee 4
Description on New Technology. ..........--+-+---- 5
Maintenance. ....... 00 eee eee eee ee eee 10
Removal of the Main Parts ......-...0202000000 10
Main Adjustments ........ 200002 eee eee ee ee 13
Block Diagram 2.0... et 20
Instruction of ICs 2... ee ee 22
Standard Schematic Diagram
(Main Amp Circuit)... ....0..0 0000. eee eee 23
(Mechanical Control Circuit)... .........2005. 24
(Computer Circuit)... 2... 2.0.00 ce eee oe tess 25
Specifications
Type : Component stereo cassette deck
Track system : 4-track, 2-channel
Tape speed : 1-7/8 inch/sec (4.8 cm/sec)
Frequency response :
(-20 VU recording)
Metal tape *1 515 — 18,000Hz
25 — 16,000Hz (+3dB)
SA/Chrome tape “2 15— 18,000Hz
25 — 16,000Hz (+3dB)
SF/Normal tape *~3 15 — 17,000Hz
25 — 15,000Hz (+3dB)
(O VU recording)
Metal tape
SA/Chrome tape
SF/Normal tape
25 — 12,500Hz (+3dB)
25 —.8,000Hz (+3dB)
25 —8,000Hz (+3dB)
Frequency response when using the
computer B.E.S.T. tuning system
(~20 VU recording)
Metal tape
SA/Chrome tape
SF/Normal tape
40 — 12,500Hz (+1dB)
40 — 12,500Hz (+1dB)
40 — 12,500Hz (+1dB)
Those values are almost the same for
all types of tapes when the computer
B.E.S.T. tuning system is used.
Note: *1..... SCOTCH METAFINE or Equivalent
AD, TDK SA or Equivalent
Ec ie MAXELL UD or Equivalent
S/N ratio : 60dB (from peak level, weighted,
Metal tape)
The S/N is improved by 5dB at 1 kHz
and by 10dB above 5kHz with ANRS
on.
(DIN 45 500 weighted)
Effect of Super ANRS :
(Normal tape) Improvement of S/N:
the same as with ANRS
Improvement of frequency response:
0 VU recording; 6dB at 10kHz
+5 VU recording; 12dB at 10kHz
Improvement of distortion:
0 VU recording; 3% or less at 10KHz
+5 VU recording; 3% or less at
10kHz
Wow and flutter : 0.04% (WRMS),
0.14% (DIN 45 500)
Page
Wiring. (1): (3) sins ON BS ee ea ee ae VS 26 ~28
Enclosure Assembly and Electrical Parts List ...... 30
Enclosure Assembly and Electrical Parts ........... 33
Mechanical Component Parts.............0.005- 34
Mechanical Component Parts List.............- 35
Main Amp P.W. Board Parts... ..... 2.000002 ee 37
Computer P.W.B., Mechanical Control P.W.B........ 38
Main Amp P.W. Board Parts List............... 39
Computer P.W. Board Parts List..............4. 42
Mecha Control P.W. Board Parts... ..........0055 45
Mecha Control P.W. Board Parts List............- 46
Other P.W. Board Parts... 0... 0. cee ee es 47
Other P.W. Board Parts List.......-....000005 48
Packing, Packing Material List, Accessories.......... 49
: 65dB (1kHz)
K3;0.4%, THD; 1.0%
(metal tape, 1kHz OVU)
Crosstalk
Harmonic distortion :
Bias : AC bias
Erasure : AC erasure
Heads : 2SA (Sen-Alloy) heads
X-cut head for recording and playback
2-Gap head for erasing
: Electronic governed DC motor (for
Capstan)
DC motor (for Reel)
: 85 sec. with C-60 cassette
: 85 sec. with C-60 cassette
: 18 ICs, 77 transistors, 1 FET
52 diodes, 12 LEDs
Motors
Fast forward time
Rewind time
Semiconductors
Input terminals
Mic jack x 2 ; Max. sensitivity; 0.2mV (-72dBs)
Matching impedance;
6002. ~ 10k92
Input jack x 2; Min. input level; 80mV (-20cBs)
Input impedance; 100kQ
Output terminals
Output jack x 2. ; Output level; 0 ~ 500mV
Output impedance; 5kQ2
Phones jack x 1; Output level; 0 ~ 0.5mV
Matching impedance;
BQ ~ 1kQ
: AC 240V, 50Hz (KD-A66A)
AC 120V, 60Hz
(KD-A66C/J)
AC 240/220/120V, 50/60Hz
(KD-A66B/E)
AC 240/220/120/100V,
50/60Hz (KD-A66U)
Power consumption : 30W
Power requirement
Dimensions : 17-3/4''(450mm)W
4-5/8" (118mm)H
13” (331mm)D
(with feet, buttons, switches)
Weight : 17.4 Ibs (7.9 kg)
Design and specifications subject to change without notice.

Features
1.
Controls and Connections
» @
0
12)
®
. X-cut SA (SEN-ALLOY)
Built-in computer B.E.S.T. Tuning System for auto-
matic adjustment of Bias, Equalization and Sensitivity
of Tape.
. Metal tape compatibility having 4 tape select positions.
. Full-logic control operation with 2 motor ID (Inde-
pendent Drive) mechanism.
record/play head for an
improved frequency response over Permalloy yet as
durable as ferrite.
_ SA (SEN-ALLOY) erase head for perfect compatibility
with Metal Tape.
. LED indication for cassette operation buttons (REC,
PLAY, PAUSE) light for the respective operation mode
so as to make checking easier.
oe 989
10.
11.
12.
KD-A66A/B/C/E/J/U
ANRS, and Super ANRS for.decreasing hiss-noise and
improving linearity at high frequency.
. 5 LED multi-peak level indicators for easy check of the
recording level.
Continuous TIMER STAND-BY mechanism for record-
ing when you are not at home using the REC-OFF-
PLAY select switch.
REC MUTE button for making a non-recorded section
on the tape program.
Memory switch for listening to the same program
repeatedly. ;
Remote control terminal (R-50E optional)
(Cramer Stance || PHONES)
cca) ce hd
POWER switch
VU meter (left channel)
VU meter (right channel)
@ Indicators (see to page 4)
@8E268 6600000
Computer START button
Computer PRESET button
Cassette holder
Tape COUNTER/counter reset button
MEMORY/AUTO REW switch
TIMER STANDBY switch
Headphone jack [PHONES]
Microphone jack (Left channel) [MIC-L]
Microphone jack (right channel) [MIC-R]
ANRS switch
TAPE SELECT switch
INPUT LEVEL controls
forward knob — left channel
rearward knob — right channel
7]
®
8066 e
®
OUTPUT LEVEL control
Cassette operation button
<< > REW (Rewind) button
>> FF (fast-forward) button
> PLAY button
a STOP button
Oo REC (recording) button
«© =~ PAUSE button
REC MUTE button
EJECT button
Voltage selector (KD-A66B/C/E/J/U)
Remote control socket
LINE IN terminals
LINE OUT terminals.
Power cord
No. 4193

KD-A66A/B/C/E/J/U
Indicators
No. 4193
Super ANRS indicator
(The LED lights when super ANRS or ANRS is ON)
ANRS indicator
RUN (wink)/READY (glow) indicator
ERROR (wink)/PRESET (glow) indicator
Multi-peak level indicator
@OS0 ©
@ Front panel assembly
@ DC solenoid
® Reel motor
@ Output level control
© Input level contro!
@ VU meter (right channel)
@ VU meter (left channel)
@ Meter cover
@ Remote bar (for power switch)
@ Computer P.W. Board assembly
@® Power switch
@® Power transformer
® Power supply integrant circuit P.W.B assembly
@® Remote control socket
@® Pin jack assembly
(Mechanical parts)
® Switch holder (left switch)
@ Supply reel assembly
@® Idler assembly
@® Ree! motor pully
@ Take-up reel assembly
@ Connector wire (for slide base)
@ Counter belt
@® Slide base assembly
@ Erase head
@® REC/PB head
@ Pinch roller assembly
@ Capstan

KD-A66A/B/C/E/J/U
Description on New Technology
Computer B.E.S.T. System
Introduction
The B.E.S.T. (Bias Equalizer Sensitivity Tuning) system
which is employed in the KD-A66 is basically the same as
the preceding KD-A8 version and has also been provided
with various improvements for an enhanced performance.
The B.E.S.T. system employs a microcomputer for the
purpose of setting the proper optimum bias current and
sensitivity for tape.
1. Bias
As seen in Fig. 1 (the relationship between distortion
rate and bias current at the 1 kHz to 7 kHz signals), the
output level decreases when a larger bias current is ap-
plied. In this case especially, the 7 kHz signal is sharply
attenuated.
Further, when the bias current is decreased, the three-
dimensional distortion increases. Accordingly, the bias
current is an important factor for determining the
frequency response and the distortion rate.
It is therefore desirable that an optimum bias current
is set for each tape.
— Bias current (uA)
200 300 400 500 600 700 800
o
=z
D 1KHz
hi
2
Qa i]
t=
3 i
O 10F '
T Set bias current value
; T7KHz
a3 |
&
2 64 \
£ \ '
c °F vot Third harmonic distor-
S44 ar tion at 333 Hz
es. Xe (250mW/level)
- | NU
2 f----4---¥, Third harmonic distor-
QO 24 o’
are Se tion at 1 kHz
Toa S160 mWitevel) Fig. 1
2. Equalizer
As seen in Fig. 2 (with each tape having its optimum
bias current set), this bias current is determined by tak-
ing into account the high-band molecular character-
istic and distortion rate of the particular tape. Equali-
zation level must then be set to obtain a flat molecular
START
16sec
16sec
Far:
l2sec
REC-* Blank Marker
Approx. |.2sec
Point to which the tape is rewound
Marker
Point to which the tape is rewound
Bias sweep spot signal
\
characteristic corresponding to that bias current.
Until now, the equalization level has been determined
by ear and an accurate tuning can only be performed
by experience.
With this tuning system, the equalization level is auto-
matically set by a microcomputer.
Frequency Distribution
o
mo}
Ovseeeee
denotes
the
type
of
the
tape.
3
5 6 | NORM CrOs Fe-Cr
ax STD. UD STD. SA STD Duad
3 6 4 | (MAXCE) (10.4) (SONY)
eS
a8
2
3 o : 20
o = 0 8 - Boece to
£
fo}
2
sseecee
eeco00o
oo
ng Ss eo
t Zo o800000 :
= $ -4 oe °
Fis
x §
xo °
es
1
:
Fig.
2
Sensitivity
In tapes, the recording and reproduction levels do not
necessarily coincide with each other. The difference
between the recording and reproduction levels appears
as a beat in the frequency response of a noise reduction
circuit such as the ANRS circuit, the Super ANRS
circuit, etc.
In this tuning system, the difference between these
levels is limited within 1 dB.
Features:
1. Automatic setting of the optimum bias current for
the tape.
2. Automatic setting of the level difference to within
+1 dB, in the case of 10 kHz high-band frequency
which tends to differ between the recording and
reproduction levels.
3. Automatic setting of the tape sensitivity to within
a +1 dB error by the ANRS circuit.
4. For tapes which cannot be automatically adjusted,
its sensitivity is indicated, thus permitting normal
recording in the state in which respective values
have been preset.
Frequency characteristic sensitivity
sweep spot signal
L6sec \1.2sec Marker Approx. |.5sec
Play REC — Blank
~+— REW
STOP
(the
tape
is
rewound
to
the
vicinity
ii
WIA
of its starting position.) PLAY —
-
.
END
+
REW
Fig.
3
No. 4193

KD-A66A/B/C/E/J/U
Operation
The operation is described in accordance with Fig. 3 (opera-
tional timing chart).
1.
No. 4193
Press the START button.
At this time, the READY LED in the display section
flickers, indicating that the computer is in operation.
The tape is rapidly fed at 1.6 sec to avoid the use of
the leader tape section.
The recorder enters the recording mode.
In this mode, a blank recording (no-signal recording) is
performed for 2.8 sec to stabilize the mechanical and
electrical systems. Subsequently, two marker signals
and eight pairs of 1 and 7 kHz test signals are recorded.
At this time, the bias current is varied 8 steps every 60
msec by +10% to -30% more than the preset value.
(The bias current, equalization level and tape sensitivi-
ty values are preset, each determined by using a stand-
ard tape.) (Fig. 4)
Preset value
Bias
current
8
step
bias
current
variations
ome
Markers
ms 1kHz 7 kHz 1 kHz
AN NK
Ae
Pe Z
Tone &
ABBHHEE
Anew e eG
ZEZeZceZes J
Markers
ze
—— 1kHz 7 kHz
1121314415 |6|7
60 msec
NY
ON
NNN
REC
Set point
Fig. 4
The tape is rewound to return to the position at the
1.6 sec lapse point from the beginning of the previous
blank recording.
Data on the tape is reproduced, and the reproduction
levels of the 1 and 7 kHz test signals are compared in
order to properly determine their coinciding step.
The microcomputer detects these coincident steps.
At this time, the recorder initiates recording and per-
forms a blank recording for 2.8 sec. Subsequently, the
recorder records the markers, and enters the 12.5 kHz
signal recording state after recording the 1 kHz refer-
ence level, and increasingly varies the equalization level
of the right channel by 8 steps very 60 msec.
Further, after recording the 1 kHz reference signal of
the left channel, the recorder increasingly varies the
equalization level. Next, to adjust the tape sensitivity,
the recorder increasingly varies the 1 kHz recording
level by 8 steps every 60 msec. The difference between
the smallest and largest levels is +4 dB. (Fig. 5)
As shown in Fig. 2, the tape is rewound to the position
at the 1.5 sec lapse from the beginning of recording;
see item 6.
Right equalizer Left equalizer Tape sensitivity
Markers
tight equalizer Left equalizer
Markers
aire! Set point
The recorder enters the reproduction mode, and the
microcomputer first compares the reproduction levels
of the 1 kHz reference signal and the 12.5 kHz signal
of the right channel.
In recording, since the 12.5 kHz signal is increasingly
varied by the right equalizer, its reproduction level will
coincide with that of the 1 kHz reference signal. Sub-
sequent to storing this coincident point, the same
operation is also performed on the left channel.
Next, the tape sensitivity is adjusted. Prior to this, the
recorder stores the reproduction level of the 1 kHz
reference signal of the right channel during recording
(item 6), and during reproducing, seeks its coincident
point with the 8-step level varied tape sensitivity adjust-
ing signal.
Is the
SERVICE switch at thé
OFF position?
Setting of preset vaiues and
auto set values
's the
START switch at the
ON position?
Setting of frequency response
sensitivity
in this
ror the first?
Rewinding the tape to
its starting position
Setting of auto set values |
Fig. 6

9. Upon completion of tuning the equalizer and the tape
sensitivity (item 8), the tape is rewound to return to
the position as described in item 1. Then, the flickering
READY LED lights continuously.
The above-mentioned operation is shown in Fig. 6.
The basic operation is as previously described. In addition,
the microcomputer is provided for the functioning of the
tape deck.
Upon application of power, the microcomputer is auto-
matically reset, thus resulting in a temporary stoppage of all
output.
SERVICE switch
This switch is used to adjust the tape deck.
The microcomputer with 7 adjustment program checks the
generation of the test signals, the variation of the bias cur-
rent, the variation of the equalization level, the variation of
the tape sensitivity, the operation of the electronic mecha-
nism, and the like.
When the SERVICE switch is at the OFF position, the
microcomputer confirms that the B.E.S.T. system is func-
tioning. At this time, the microcomputer emits those auto
set values when the B.E.S.T. system completes operation
and emits the preset values even if an error occurs during
the operation. Thus, even when the auto setting of the res-
pective values is impossible, normal recording is possible
since the preset values are emitted.
Subsequently, the microcomputer waits for the START
switch to be pressed. When this switch is pressed, the micro-
computer sets bias current, equalization level and tape sen-
sitivity values.
In this process, when auto setting is impossible, the micro-
computer returns to the bias setting mode to re-tune. At
this time, when an error recurs, the red PRESET LED flick-
ers and the preset values are emitted.
In addition, irrespective of presence or absence of error, the
tape is rewound to its starting position. As a result of this,
the tape is effectively used. In normal auto setting of the
respective values, the rewinding time is about 25 sec.
Operating Principle of Respective Sections
KD-A66A/B/C/E/J/U
1. Setting of bias current
Fig. 7 represents the bias current varying circuit em-
ployed in the KD-A66.
The bias oscillation circuit consisting of transistors
X701 and X702 supplies current to the erase head and
also activates the bias amplifier consisting of transistors
X703 and X704. As the supply voltage for this bias
amplifier is changed in 8 steps by a control signal from
the microcomputer, the bias current is changed in 8
stpes.
When the binary control signal from pins 2, 3 and 4 of
microcomputer (ICKO1) is applied to IC701 which
includes 8 electronic ON/OFF switches of 8 circuits,
any one circuit alone is turned on. At this point, the
base current passes across a specific one of transistors
X709 — X716 turning it on.
Concerning transistor X708 which controls the supply
voltage for the bias amplifier, its base voltage is deter-
mined by a divided voltage by R728 and the associated
collector resistance of X709 to X716.
The bias oscillation circuit, which is turned on/off by
the BMUTE signal from pin 304 on the computer
circuit board, is also turned on/off by the NSTOP
signal (the control signal of the brake and solenoid)
from pin 512 on the same board when stopping the
bias oscillator circuit operation during the PAUSE
mode.
+VCCRI
TO HEAD
Equalization level
change-over signal
Tape sensitivity
change-over signal
Fig. 8
2. Setting of equalization level and tape sensitivity Fig. 8
represents the recording amplifier section employed in
the KD-A66.
The input signal is attenuated by resistor RO and any
of resistors R1 — R16 and entered into the specific
transistor. At this time, a tape sensitivity select signal
emitted from the microcomputer causes the respective
resistor in the group of R1 — R16 to be grounded, thus
determining the attenuation level. The select signal is
transmitted in the form of 4 binary bits and converted
into decimal bits. In addition, a CMOS IC incorporat-
ing analog switches is used in the select switch unit to
protect the audio signal against distortion. This select
switch unit permits the change in recording level of +4
dB.
No. 4193

KD-A66A/B/C/E/J/U
No. 4193
The LC resonance peaking circuit mounted in parallel
with the emitter resistor of the recording amplifier
transistor boosts the high frequency of the recording
amplifier transistor. With a normal tape, the output
level of a 10 kHz signal is higher by about 9 dB than
that of a 1 kHz signal.
To avoid this problem, the selection of the capacitor in
the peaking circuit is performed to vary the compensa-
tion of high frequencies. In this case, the microcom-
puter emits a 3 binary bit signal, decodes it in 8 steps
and switches the appropriate analog switch in the
CMOS IC. Thus, the recording level is selected in the
range of +4 dB.
Fig. 9
Peak hold A/D converting circuit
In the KD-A66, a 12.5 KHz frequency is selected as the
equalizer tuning frequency to improve high band
frequency response. In a cassette tape deck with high
frequencies, the changes in levels such as are caused by
dropout, etc. are enlarged due to the base material of
the cassette tape and/or the wound state of the cassette
tape. If the optimim state is decided by the reproduc-
tion level such as in the B.E.S.T. system, this level
change causes incorrect setting of the respective values.
To avoid this problem in the KD-A66, a peak hold A/D
converter has been developed by the combination of a
peak hold circuit and a charge/discharge: circuit.
The peak hold A/D converting circuit permits stable
level detection even against high frequency dropout.
Block diagram is shown in Fig. 9 and timing chart in
Fig. 10.
The input signal is classified into a left or right channel
signal in IC801 by the Lch signal from the microcom-
puter, amplified by 1C802A and entered into the peak
hold circuit consisting of 1C802B, C802, D802 and
X805, which in turn detects the negative component of
the input signal accumulating at capacitor C802.
In the KD-A66, upon completion of the 40 msec oper-
ation of the peak hold circuit, $3 and S4 in 1C801 are
turned on by the ADC signal from the microcomputer.
Since $3 functions to apply +5V to the positive input
side of 1C802B, the output of 1C802B is clipped to
+5V and the loop in the peak hold circuit is opened by
diode D802.
At the same time S4 is turned on and capacitor C802 is
charged from the constant current source I1. Since a
constant current is supplied to this capacitor, the volt-
age in it linearly increases in the form of V=I1 x Time/c
+ Vo (initia! voltage).
Since capacitor C802 has been supplied with the
negative component of the input signal, when the volt-
age in it rises with the constant current charge, IC803A
detects the moment that this voltage exceeds OV, and
transmits that detection signal as an ADT signal to the
microcomputer.
The microcomputer measures the time from when the
40 msec peak hold operation is completed to when the
above voltage exceeds OV, to measure the signal level.
Fig. 10 is the timing chart. Here the input signal is sub-
ject to peak holding during the 40 msec period and
the constant current discharge is performed and the state
of OV excess is shown. AD1 is a normal signal, but this
indicates that stable measuring is possible should level
change (decrease) occur halfway as in AD2 and AD3.
WN A
ADC Teal fea AD3 ]
x805 —— :
+ <--| ae /
ft |
|
Marker signal detection
When recording while tuning the bias current, equaliza-
tion level and tape sensitivity, marker signals first enter
as shown in Figs 4 and 5. A 40 msec signal of 1 kHz
+50 dB is recorded two time as the marker signals with
a 40 msec blank between.
In the B.E.S.T. system, when the tape is rewound after
recording the test signals, it returns to its starting posi-
tion while counting the pulses from the tape counter.
This counting is not as accurate as when locating a 60
msec signal. For more accurate counting, the deck
waits for the said marker signals to appear in the repro-
duction state after rewinding the tape.
After the input signal is amplified by 1C802A in Fig. 9,
it is compared with -0.5V of IC803B in Fig. 5.
When this signal is entered, the output from IC803B is
inverted from +5V to -5V, thus transmitting the arrival
of the marker signals to the microcomputer.
After detecting the marker signals, the microcomputer
chekcs their pattern to discriminate the test signals,
thereby preventing faulty operation due to external
noise and ensuring accurate signal location.

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Fig. 11
Microcomputer
In the KD-A66, the tuning function is controlled by
the 42-pin LSI microcomputer which stores instructions
of about 2000 steps and processes normal instructions
at 10 msec. The connection diagram is shown in Fig.
11. In addition, its incorporated timer controls the
timing of the entire deck. The process is performed in
the P-channel MOSFET and the output is used in the
form of an open drain type pull-down.
The clock circuit stably operates because it consists of
an LC resonance circuit. Since the microcomputer is
provided with an interruption function, the pulse from
the tape counter is counted with interruption.
Auto-stop
The rotation pulse signal from the Hall IC is waveform
rectified and differentiated at its leading and trailing
edges. Then, the monostabie multiple circuit generates
a pulse of about 20 msec which is in turn applied to
the interrupt terminal INT of the microcomputer.
The microcomputer detects the tape position by the
rotation pulse signal and also generates an auto-stop
signal if no signal is applied for 1.5 sec or more.
Auto-rewind circuit
In the KD-A66, when an auto-stop signal is emitted
from the microcomputer (ICKOI) at the tape end
during playback or record, the tape is automatically re-
wound to the beginning and the deck enters the PLAY
or STOP mode by switching the MEMORY switch
(SW55)}.
KD-A66A/B/C/E/J/U
If the tape counter displays “999” halfway, since the
deck also enters the PLAY or STOP mode, the data in
the tape can be repeatedly reproduced between “‘0°’
and ‘‘999’’. To describe this operation, the MEMORY
switch (SW55) is set in the PLAY mode. AT first, when
an auto-stop signal is emitted from the microcomputer
at the tape end during playback, transistor XKO6 goes
on, thus lowering the voltage at the auto termina! (pin
5) of mechanism contro! 1C51. At this time, the auto-
rewind instruction is emitted from 1C51.
When the tape is rewound to the beginning by this
instruction, the auto-stop instruction is emitted from
pin 12 of the microcomputer. Likewise, when the volt-
age at the AUTO terminal (pin 5) of I1C51 is lowered,
the PLAY instruction is automatically emitted from
the microcomputer.
Next, to describe this operation, the MEMORY switch
is set in the STOP mode, At first, when an auto-stop
signal is emitted from the microcomputer at the tape
end during playback, transistor XKO6 goes on, thus
lowering the voltage at the said AUTO terminal. At this
time, the auto-rewind instruction is emitted from 1051.
When the tape is rewound to the beginning by this
instruction, the auto-stop instruction is emitted from
pin 12 of the microcomputer. However, since the base
voltage of tansistor X63 is kept to about 1V during the
REW instruciton, the emitter voltage of transistor X63
is lowered to 0.2V when transistor XKO6 goes on. At
the same time, transistor X63 goes on and functions to
pull the STOP terminal (pin 1) of 1C51, thus entering
the deck into the STOP mode.
In addition, with the MEMORY switch in the OFF
state, the auto-stop signal from the microcomputer,
when transistor XKO6 goes on, passes across diode D63
and also functions to pull the STOP terminal (pin 1) of
1C51, thus entering the deck into the STOP mode.
Since the MEMORY STOP/PLAY function can be per-
formed even during the auto-rewind operation by the
auto-rewind circuit, the data in the tape can be re-
peatedly reproduced between ‘999” in the tape
counter and the tape end.
XKO6 4 [_ VMwis37-001v |
STOP] R38
No. 4193

KD-A66A/B/C/E/J/U
Maintenance
To get long, trouble-free service, maintenance is important.
Do not forget cleaning and demagnetizing.
Cleaning
After
Jong
use,
the
heads
and
tape
part
—
capstan,
pinch
roller,
etc.
—
will
become
dirty
with
dust
or
magnetic
parti-
cles.
Dirty
heads
cause
imperfect
erasing
or
high
frequency
drop-off.
A
dirty
capstan
and
pinch
roller
will
cause
un-
stable
tape
speed,
leading
to
increased
wow
and
flutter.
Always
keep
them
clean
by
following
the
procedure
below.
1. Heads
1)
Push
Eject
button
to
open
the
cassette
holder.
2) Use the head cleaning stick-provided to wipe the sur-
face where the tape comes into contact with the head.
(It is effective to moisten the cotton with alcohol.)
2. Pinch roller and capstan
Do the same method as heads.
3. Cabinet
When
the
cabinet
becomes
dirty,
wipe
it
with
a
soft
cloth
soaked
with
a
neutral
cleaning
solution
of
a
polishing
cloth.
*
Do
not
use
thinner
or
benzine.
Demagnetizing
The
heads
are
made
from
a
material
resistant
to
magnetiza-
tion
but
after
long
use
they
may
become
magnetized.
A
magnet
brought
into
their
vicinity
can
magnetize
the
heads,
causing
excess
noise.
If
noise
seems
to
have
increased,
demagnetize
the
heads
with
a
head
demagnetizer
through
the
following
procedure.
1. Turn the POWER switch OFF.
2. Wrap the tip of the demagnetizer with vinyl tape or
soft cloth so as not to damage the head surface. Switch
on the demagnetizer and bring it close to the head.
3. Move the tip of the demagnetizer slowly first to the
left and right, then up and down in front of the head.
Gradually move it away from the head and switch it
off at a distance of more than 30 cm (12”).
4. The erase head need not be demagnetized. The capstan
shaft and tape guide should be demagnetized in the
same way as the record/playback head.
Do not bring a magnetized metallic object (a screw-
driver, for example) near the head as this will increase
noise.
No. 4193
Removal of the Main
Parts
Observe
care
in
handling
the
parts
since
the
parts
are
small
in
size
and
the
distance
between
them
are
short
due
to
a
deck
design
aimed
mainly
at
compactness
and
high
per-
formance.
ENCLOSURE ASSEMBLY PARTS
@.
Cassette
door...
.Depress
the
EJECT
button
to
open
the
cassette
door
Slide
off
the
cassette
door
upwards
(about
5
mm)
to
unlock
its
pawls
of
both
sides.
Remove
the
cassette
door
forward.
Eject button
Fig. 13
@
Topcover......
Remove
4
screws
fastening
the
top
cover.
Control
knobs
(INPUT
LEVEL,
OUTPUT
LEVEL)
and
Lever Knobs (ANRS, TAPE SELECT)
otalGeiah © wl edn Bees Pull off them forward.
Screws
Fig. 14
Lever knobs Control knobs
@ Bottomcover....Remove 5. screws fastening the
bottom cover.
@ Mecha. control switches assembly .....
(When adjusting or replacing REC/PB heads or Erase
head)
Remove 3 screws positioned below the mecha. control
switches (on the bottom of the deck) and pull the
control section forwards — no need of removing the
front panel assembly.
@ Front plate assembly .....
1) Remove a screw fastening the bracket to mechanical
assembly.