JVC KD-A77 A User manual

JVC
MODEL
KD-A77 A/B/C/E/J/U
STEREO CASSETTE DECK
No. 4186
September 1979

KD-A77A/8/C/E/J/U
r-
Contents
Specifications
.........................................................
2
Features
..................................................................
3
Controls and Connections
..........................................
3
Main Parts Location
...................................................
4
Maintenance
............................................................
4
New
Technique
......................................................
5
Removal
of
the Main Parts
..........................................
6
Main
Adjustments
...................................................
10
Block Diagram
......................................................
16
IntegrantCircuit
......................................................
18
Standard Schematic Diagram
of
KD-A
77
Amplifier
circuit
................................................
19
Mecha. control
circuit
..........................................
20
Wiring
Connection
(1
)
of
KD-A77
..............................
21
Specifications
Type
Track
system
Tape speed
Frequency response
OVU
Metal
tape
SA/Cr02
tape
-20VU
Metal
tape
SA/Cr02
tape
*
1
*2
SF/Normal tape
*
3
SIN ratio
Stereo cassette
deck
4-track,
2-channel
1-7/8
inch/sec
(4.8
cm/sec)
25-12500Hz
±3dB(Typical)
25
-
8000Hz
± 3dB(Typical)
15-20000Hz
25
-1
8000Hz
± 3dB(Typical)
15-20000Hz
25-
1
8000Hz
± 3dB(Typical)
15-19000Hz
25-17000Hz
±3dB(Typical)
Surpases DIN
45
500
60dB (from peak level, weighted,
Metal tape)
The SIN is improved by 5dB
at
1kHz and by
10dB
above 5kHz
with
ANRS on.
(DIN
45
500
weighted)
Effect
of
Super ANRS : (normal tape)
Improvement
of
SIN : the same
as
with
ANRS
Improvement
of
frequency response
:
OVU
recording; 6dB
at
10kHz
+
5VU recording; 12dB at 10kHz
Improvement
of
distortion
Wow
and
flutter
Crosstalk
Hormonic
distortion
Bias
Erasure
Heads
No.4186
OVU
recording;
3% or less
at
10kHz
+
5VU recoridng;
3% or less at 10kHz
0.04%
(WRMS),
0.14%
(DIN
45
500)
65dB
(1
kHz)
K3;
0.4%,
THD:
1.0%
(metal tape, 1kHz OVU)
AC bias
(85kHz)
AC erasure
(85kHz)
3 heads
SEN
ALLOY head
for
recording,
SEN
ALLOY X
cut
type
for
playback and
two-gap
SEN
ALLOY head
for
erasure
Wiring Connection (2)
of
KD-A77
..............................
22
Enclosure
Ass'y
and Electrical Parts
...........................
25
Enclosure
Ass'y
and Electrical Parts List
..................
23
Mechanical Components Parts
.................................
26
Mechanical
Components
Parts List
........................
28
Printed Wiring Board Parts
Main
Amp.
P.W. Board Parts
....................................
33
PowerSupply P.W. Board Parts
.................................
34
Main
Amp.
P.
W.B
Parts List
.................................
30
Power
Supply P.W.B Parts List
..............................
35
Other
P.W.B Parts
...................................................
37
Other
P.
W.B
Parts List
.......................................
39
Packing
......................................................
Back cover
Accessories
................................................
Back cover
Motors
Fast
forward
time
Rewind
time
Semiconductors
Input terminals
Output
terminals
Power requirement
Power consumption
Dimensions
Weight
FG
type
DC
servo
motor
(for
Capstan)
DC
motor
(for
Reel)
85
sec.
with
C-60
cassette
85
sec.
with
C-60
cassette
18 ICs,
49
transistors,
59
diodes,
14
LEDs
Mic jack x
2,
Max. sensitivity;
0.2mV
(-72dBs)
Matching impedance;
6000-10kO
Input jack x
2,
Min. input level;
80mV
(-20dBs)
Input impedance;
100kO
Output
jack x
2,
Output
level;
0-300mV
Output
impedance; 6kO
Matching impedance:
50kO or more
Phones jack x 1,
Output
level;
0-0.5mW/SO
Matching
impedance:
80-1
kO
AC
120V,
60Hz
(KD-AnCW
AC
240/220/120V,
50/60Z
(KD-A
n
A/B/E)
AC
240/220/120/1
OOV,
50/60Hz
(KD-A77U)
36W
17-3/4"
(450
mm) W
4-3/4"
(120
mm) H
12-7/16"
(316mm)D
18.3
Ibs
(8.3
kg)
Note:
*
1 ... SCOTCH METAFINE or Equivalent
*
2 ... TDK SA or Equivalent
*
3 ... MAXELL
UD
or Equivalent
Design and specifications are subject
to
change
without
notice.
- 2 -

Features
1. 3 SA (SEN-ALLOY) heads
Combined
SA (SEN-ALLOY) record/play (X-cut type)
heads make possible record monitoring. The erase
head is a 2-gap head also made
from SA (SEN-ALLOY).
2. Two-motor ID (independent Drive) mechanism
This mechanism incorporates a
newly developed Back
Tension
system which gives improved tape contact
with the head.
3. Self-illuminated buttons for full logic mechanical
operation (excluding STOP or REC-MUTE modes.)
4. Three position Metal-Tape-Compatible tape select
switch.
METAL -FeCr _ SA/Cr02
NORM
(Automatic switching between SA/Cr02 and NORM)
5. The
REC MUTE button is at the right side of the
mechanical operation buttons.
KD-An A/B/C/E/J/U
6. ANRS which reduces tape hiss to an inaudible level
and Super ANRS
which improves linearity at high fre-
quencies are incorporated.
7. MEMORY/AUTO REW switch
8. Recording equalizer switch
9. Timer standby capability for automatic recording or
playback using an
AC timer.
10. Geared and oil-damped cassette holder.
11. New Metal-Tape-Compatible multi-peak level in-
dicators (+ 9dB, + 6dB, + 3dB, -2dB, - 7dB).
together with back-lit VU meters with the expanded
coverage
from + 7VU to - 20VU, make level observa-
tion easier.
12. OUTPUT volume (for LINE and HEADPHONES use)
13. Remote control terminal (for the optional remote con-
trol unit -R-30E).
Controls and Connections
2 3 4 5 6
10 11 12
14 15 16 17 18
19
20
21
==
==
==
==
==
==
==
==
==
==
r-
==
. .
==
'-
1. VU meters and Multi-point peak level indicators
2. INPUT LEVEL control
3. TAPE indicators
4. ANRS/Super ANRS indicators
5. Cassette holder
6. MEMORY/AUTO REW switch
7. Tape counter/counter reset button
8. EJECT button
9. TIMER STANDBY switch
10. PHONES jack
11. MIC jacks
12. INPUT SELECT switch
13. ANRS switch
14. TAPE SELECT switch
15. REC EQ switch
1 6. OUTPUT LEVEL control
n
LJ
•
22
23 24
[f]
r~:f
~1 r
-[ ~ I
17. MONITOR switch
18. Cassette Operation buttons
~~ REW (rewind) button
~~ FF (fast forward) button
~ PLAY button
• STOP button
o REC (record) button
11 PAUSE button
REC MUTE button
19. POWER switch
20. Power cord
21. Voltage select switch (KD-A 77 A/B/E/U)
22. REMOTE CONTROL socket
23. LINE IN (REC) terminals
24. LINE OUT (PLAY) terminals
- 3 -
No.4186

KD-A77 A/B/C/E/J/U
Main Parts Location 2 3 4 5 6
7
9
"-------- 8
11 12 13
(Mechanical parts)
1. Front panel assembly 1. Switch holder (U
2. DC solenoid for playback 2. Supply reel ass'y
3. Reel motor 3. Idler ass'y
4. Geared and oil-damped brake ass'y 4. Reel motor ass'y
5. Variable resistor (INPUT LEVEL control) 5. Take-up reel ass'y
6. Meter cover 6. Switch holder (R)
7. LED P.W. Board ass'y 7. Connecting wire (for play solenoid)
8. Hall element P.W. Board ass'y 8. Capstan
9. Power switch 9. Slide base ass'y
10. Power transformer 10. Stad with pad (for back tension)
11. Remote control socket (DIN socket) 11. Erase head
12. Pin jacks ass'y 12. Combined SA (SEN-ALLOY) record/play heads
13. Mecha. control P.W. Board ass'y 13. Pinch roller ass'y
Other mechanical parts are the same as location of model KD-A6:
Please refer to the service manual 0 KD-A6 A/B/C/E/J/U (No. 4179 -page 4).
Maintenance
To get long, trouble-free service, maintenance is important.
Do not forget cleaning and demagnetizing.
Cleaning
After long, the heads and tape part -capstan, pinch roller,
etc. - will become dirty with dust or magnetize particles.
Dirty heads cause imperfect erasing or high frequency
drop-off. A dirty capstan and pinch roller will cause
unstable tape speed, leading to increased wow and flutter.
Always keep them clean by following the procedure below.
1. Heads
1) Push the EJECT button to open the cassette holder.
2) Push up the transparent cover to remove it.
3) Use the head cleaning stick to wipe the surface where
the tape comes into contact with the head.
(it is effective to moisten the cotton with alcohol.)
2. Pinch roller and capstan
Close
the cassette holder with its transparent cover remov-
ed. Press
the tape detection pin inside the cassette com-
partment and set the deck in the playback mode. Insert the
cleaning stick into the hole on the right side at the bottom
of the cassette holder and clean the pinch roller and
oop"an. ~~:,"'h "",,
~.~
Cleaning stick
No.
4186
- 4 -
3. Cleaning the cabinet and panel
Wipe the cabinet and panel clean with a soft cloth dipped in
a neutral cleaner. Do
not use thinner, benzine, alcohol or
other strong solvents, as these will cause damage to the
surface finish of the cabient and panel.
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 inceased,
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 of 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 (1 2").
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 screwdriver
for example) near the head as this will increase noise.
Oiling
Feed one or
two drops of machine oil to pinch roller shaft
once or twice a year under normal conditions of use.
Avoid oiling them excessively, or rotation may become ir-
regular because
of oil splashes.

New Technique
Combination SA heads for recording and playback (Fig. Al
Due to its high recording density, Metal Tape requires
recording and
playback heads that are made of materials
having a greater maximum magnetic flux density than con-
ventional ferrite or permalloy. The combined
record/playback heads, newly developed for the KD-A 77,
both employ SA (Sen-Alloy) to ensure high performance.
The SA head has advantages over conventional heads in
various fields
such as fewer core loss, greater gap ac-
curacy, better wear and corrosion resistance. However,
its biggest feature is its high maximum magnetic flux densi-
ty. Because of this, the SA head can bring the most out of
the superior performance of Metal Tape. This is especially
true for its extended frequency response at high frequen-
cies;
something that has never been possible to realize with
usual cassette tapes.
The playback head incorporates a unique X-cut core struc-
ture to improve the characteristics of the low frequency
range. With ordinary core configurations, playback output
is subject to peaks and dips in the low frequency range as
shown in Fig. B. This is called the "contour effect". :this
effect is caused by interference between the length of the
tape-to-head contact area and the wavelength of the recor-
ding frequency. With the X-cut design the core is cut
diagonally to enable the tape to leave the head, not abrupt-
ly, but with a gradually lessening contact area.
The result is, as shown in the diagram, reduction of the
contour effect. (Fig. C)
Configuration of record/playback combination SA heads
CD SA recording head
® 4/lm gaps
® 1/lm gaps
Fig. A
® X-cut SA playback head
® SA chips
® Shield plate
rJ) Zinc die-casting head base
- 5 -
KD-A77 A/B/C/E/J/U
Comparison between characteristics of conventional cut
core and X-cut core
c
onventlona
I h d . h
ea Wit
standard core constructi on
in
~
-.
QJ
>
~
...
:J
B-
:J
0
-11
16
10
@~
I
:J
/
~
/
/,1./
Usign standard curre
/ I I I I I
,
nt recorded tape
10 .0 70 100 100 .00
Frequence (Hz)
Fig. B
X -cut core construction
in
:9
a;
>
~
...
:J
Cl.
...
:J
0
11
16
10 t--off----+ Using standard current recorded tape
I I I
10 .0 70 100 100 .00
Frequence (Hz)
Fig. C
Note: SA (Sen-Alloy) is a trademark of JVC.
No.4186

KD-An A/B/C/E/J/U
Removal of the Main Parts
This cassette deck which features a compact design and high performance uses miniature sized parts which are closely ar-
ranged.
Take special care
when servicing it.
.11
Q
~
~--~.
~~~;;;;;:;;.;...f='.
Lever knobs
Screws
(Top view)
Screws
(Bottom view)
Screw
Screws
Screw
l'
Enclosure assembly
1. Cassette door .....
Push the EJECT button to open the cassette door. Slide
it upwards (approx. 5 mm) to unlock its pawls, and
remove it to frontward.
2. Lever knobs (INPUT SELECT, ANRS, TAPE SELECT,
MONITOR) and level control knobs (INPUT LEVEL - L
and
R, OUTPUT LEVEL and REC EQ)
Pull them to frontward
3. Top cover .....
Remove 6 screws fastening the top cover.
4. Bottom cover
Remove 7
screws fastening the bottom cover.
5. Front plate assembly
1) Remove 5
screws (3 screws on upper side and 2
screws on bottom side) fastening the front plate
assembly
2) Remove TAPE & ANRS indicators wires socket.
When adjusting or replacing REC/PB heads or Erase
head .....
1) Remove the wires of the control switches from the
wire clamp and 2 wire sockets after having removed
the top cover.
2) Remove 2
screws positioned below the control swit-
ches (on the bottom of the deck) and pull the control
section
forwards -no need of removing the front
panel assembly.
Front Caution
No.
4186
- 6 -
When assembling the control switch assembly to the
front panel, do in the order of the numbers as below as
not to damage the front panel.
1) Wrap the sharp edges of the front panel with vinyl
tape, etc.
2) Insert the control switch assembly in the front panel.
3) Remove the vinyl tape.
4) Fasten 2 screws for the control switch assembly.

Gear frame ass'y ,CD
P.W.B holder
® Push
Screws
Screws
(Bottom view)
- 7 -
KD-A77 A/B/C/E/J/U
Door brake and its related parts
1. Gear frame ass'y ..... Remove 2 screws CD.
2. Brake arm and tire ..... Remove the E-ring and torsion
spring ®.
3. Spur gear and brake drum ..... Remove the E-ring, and
spring
@.
4. Rack plate ..... Remove the screw and the collar @.
5. Brake lever ass'y ..... Remove the E-ring @.
Electrical parts
1. Power supply P.W.B. parts assembly.
1) Remove a pawls of P.W.B. holder in the order of the
numbers in the illustration arrow mark.
2) Remove 3
screws fastening the P.W. Board.
3) Open the P.W.B to upper side.
2. Main amp P.W.B parts assembly
1) Remove 4
screws fastening the main amp. P.W.
Board (on
the bottom side).
2) Remove 4 screws fastening the lever switches on the
front bracket.
3) Remove 5 washers and 5 nuts fastening the
PHONES, MIC-L, MIC-R jacks and REC EO, OUTPUT
LEVEL control shafts.
No.4186

KD-A 77 A/B/C/EIJ/U
~ckPlate
Screws -----,rl-I~rv I
(Top view)
Screws
Power switch
Screws
Screws
(for door brake
related parts)
tIP_--_Screw
(Right side)
No_4186 - 8 -
3. Power switch
1) Remove the lock plate CID holding the remote bar.
2) Remove a
screw ® fastening the power switch
bracket.
3) Remote 2 screws (j) fastening the power switch.
4. Power transformer
Remove the 2 screws and 2 washers fastening the
power transformer.
Removal of the mechanical assembly
1. Remove a screw fastening the arm of gear-oil damper
(Left side of the cassette holder), and Remove 2 screws
fastening the gear frame ass'y to Remove door brake
related parts.
2. Remove 5 screws fastening the mechanical bracket to
the amp. chassis (Right - 2 p.c.S, Left - 3 p.c.s).
3. Remove a screw fastening the counter bracket to the
front bracket.

(Top view) Screws
..
(Front view)
(Rear view)
- 9 -
KO-An A!B!C!E!J!U
4. Remove 2 screws fastening the joint bracket to the front
panel (upper side).
Removal of the mechanical parts
1. REC/PB head .....
Remove the screw CD for head adjustment.
Remove the screw CV.
2. Erase head .....
Remove the screw ®.
Remove the screw ®
3. Pinch roller arm ass'y :.... Remove the E-ring @.
4. Supply reel disc ..... Pull out the reel stopper @.
5. Take-up disc ..... Pull out the reel stopper (j) .
Remove the counter belt.
Note:
1) Remove the reel disc stoppers with a piece of sheet
metal inserted between the reel disc and the stopper.
2) Be careful not to stain the counter belt.
6. Reel
motor ..... Remove the 3 screws ® fastening the
reel motor.
7. Capstan motor .....
1) Remove the screw ® fastening the rubber stopper.
2) Remove its motor belt.
3)
Turn the motor counter clockwise and pull it for
removal.
Note:
When replacing the motor, check the following items.
1) Is the motor placed in the correct position?
(Don't deflect the motor at mounting it.)
2) Does
the capstan belt run in the center of the motor
pulley?
3) Does
the capstan belt run in the center of the flywheel?
No.4186

K D-A 77 AIBICIEI J/u
Main Adjustments
[I] Equipment and measuring instruments used for adjustment
1. Electrical adjustment
1) Electronic
voltmeter
2) Audio frequency oscillator
(range; 50 - 20kHz and output OdB with impedance
600fl)
3) Attenuator
4) Standard tapes for RECIPB
Maxell UD -
SF tape (for normal) }
TDK SA - SA tape (for Cr02) or equivalent
SCOTCH METAFINE - Metal tape
5) Reference tapes for playback (JVC Test Tape)
VTT-658 (for head azimuth adj.)
VTT-656 (for motor speed, wow flutter adj.)
VTT-664 (for Reference level 1kHz)
TMT-6002N (for playback frequency response)
6) Resistors
1
oon (for measurement of the bias current)
600n (for attenuator matching)
2. Mechanical adjustment
1) Gauge
for checking the head position.
2)
Torque gauge.
3) Blank tape (C-120) for tape running checker.
[11] Mechanical adjustment
Head adjustment
KO-A77
Back-tension pad Pad
(attached to the cassette) Tape
Clearance (A)
1. After installing the specified parts in the appropriate
positions:
A. Snug screw CD gently, then back off about two
turns. This makes the heads nearly horizontal.
B. Snug screw @ gently, then back off about one turn.
This will roughly position the tape in the center of the
tape path.
For
tightening screw @" use a home make screwdriver,
filed down to the specifications shown below. The same
screwdriver can be used to tighten screw (1).
Screwdriver
Pinch roller
Combination head
2. Make sure that the moving part of the erase head
assembly
moves smoothly around the pivot of screw @
and also confirm that there is enough clearance (A) in
the play mode.
3.
Next, make an operational adjustment. Load a C-1 20
cassette and adjust the height of the erase head by turn-
ing screw @. Watching that the tape does not curl at
the guides of both the combination and erase heads is
indication
of proper adjustment.
Correct
-1 Tape guide
t-Tape
Incorrect
f
Tap€ guide --, Tape guide
Tape l
__ ' _~-- Tape
No.4186
-10 -

KD-A77 A/B/C/E/J/U
Item Adjustment
Adjusting Standard
Remarks
point value
Adjusting Connect a speed meter to the LINE Semi-
3000Hz
If the speed meter functions as a wow
motor speed
OUT
terminals. Play back the fixed
and flutter meter, also, connect the
VTT-656 test tape.
resistor deck to the INPUT terminals of the
Adjust the semi-fixed resistor on the on the meter.
motor P.W. board until the reading of motor
the speed meter
is
3000Hz. P.w.
board
Checking play- Employ a
torque testing
cassette
40-70 If the standard torque is not obtained,
back torque tape for the checking, or remove the
gr-cm
replace the take-up disc assembly.
cassette cover
and use a
torque
gauge.
Checking fast
Measure the torque in the fast for- More If the standard torque is not obtained,
forward torque
ward mode in the same manner as in than perform the following.
the above. 70 gr-cm 1. Clean the capstan belt, the idler cir-
cumference, the motor pulley, the
take-up reel disc circumference,
the flywheel circumference, etc.
2. Replace the belt and idler.
Checking re- Measure
the torque in the rewind More If the standard torque is not obtained,
wind torque mode in the same manner as in the than clean the capstan belt, idler, motor
above. 70 gr-cm pulley, flywheel circumference, rewin-
ding idler circumference, left reel disc
circumference, etc.
Checking wow
Connect a wow and flutter meter to
If the reading becomes moving value
and flutter
the LINE OUT terminals. even
if conforming to the standard, a
Play
back the VTT-656 test tape. re-claim may be raised. Repairs are
Check to see if the reading of the
necessary.
meter is within 0.04% (WRMS).
[Ill] Repair of wow flutter
If wow and flutter increase, check the following points.
If there is defect in revolving parts, the wow and flutter
generated will increase in proportion to the number of
revolutions.
Play a 3000Hz test tape, and defective part can be
detected from the sound.
Section Trouble Repair
Capstan and
flywheel
Capstan shaft has excessive run-out Replace flywheel.
Flywheel turns heavily. Clean the capstan shaft and the groove in the
(shaft seisure,
thrust
play, etc.) flywheel.
Apply oil to the metal position.
Replace the capstan assembly.
Pinch roller Rough
rotation (Deformation scrat- Replace pinch roller, or pinch roller spring.
ches, or dust) Clean
the pinch roller or apply oil to the rotary
The angular position of the pinch roller shaft.
is
not correct. Adjust the pinch roller so that it is parallel with
The pinch roller pressure is not correct. the capstan shaft.
Replace
the pinch roller spring.
Belt Belt has undue run-out. Clean
the belt.
Belt is dirty or slippery. Replace the belt.
Back tension Back tension
is irregular, or back ten- Replace back tension spring (under supply disc).
sion is too strong.
Motor
Motor shaft has undue run-out. Replace motor.
Motor pulley is oily and dusty. Clean motor pulley.
Damping gear oil
Oil employed -Torque grease specified by JVC (KANTO KASEI GP-608)
Applying method - Apply in both concaved sections as shown in the figure.
-11-

K D-A 77 A/B/C/E/ J/U
[IV] Adjustment Location of Electrical Circuit
No.4186
Power Supply P.W. Board
Front
l]-R
'~' _1 .,,' '" m ... om"'''''" ',,""'m,m _
U L (Turning in the direction of the arrow Increases the deflection angles.)
t
VR302 VR801
(3-R
VR701
For playback level adjustment.
\G-L
(Turning In the direction of the arrow increases the playback levels.)
VR803
11 _____ L _ For playback frequency response adjustment
,,~ (Turning In the direction of the arrow Increases the signal current)
VR703Rtl
Q-
L For ANRS adjustment at playback mode
_ __# '-----------.J (Turning In the direction of the arrow Increases the ANRS gains.)
Main P. W Board
VRAOl
VR501
T.;-L VR601 GL
For recoridng level adjustment. ·0 ~ Rl
T.P-R
(Turning in the direction of the arrow in-
creases
the recording levels.)
1
Front
L ] For ANAS adjustment at recording mode.
(Turning in the direction of the arrow increases the ANRS gains.)
VRBOl
(eR
VR504 VR502 VR503
((~((~G- L Jero, t-For bias CUrrent adjustment.
(Turning in the direction of the arrOw in-
QQ G-
v: creases
the bias current value.1
VR604 VR602 603 r
I LL'::=~==rNORM~
I R I IJ
L I METAL
R---~
In nl
n n
~12~

KD-A 77 A/B/C/E/ J/U
[V] Electrical circuit adjustment procedure
In the steps marked by an asterisk (*), adjustment should be performed, however, only checking is sufficient with steps
other than those.
Adjustment should be performed in the order of steps 1, 2, 3 .....
Perform these adjustments with the ANRS switch set to OFF and with the OUTPUT level control set max.
Step Item
1* Adjusting
2*
3*
4*
playback
level
Adjusting
playback
frequency
response
Adjusting
VU
meter
sensitivity
Adjustment
record/
playback
frequency
response
Adjustment
1. Play back the VTT-664 Reference
tape
(1 kHz) with Tape select
switch set to the NORMAL posi-
tion.
2. Adjust VR701 and VR801 until the
LINE OUT becomes about -8dBs.
Play back
test tape, TMT-6002N
for following againstment.
1) Adjust VR702, 802 so that 10kHz
signal and 1kHz signal gains be-
come
flat response.
1 .Set
the cassette deck to its source
mode.
2
.Apply a 1kHz, approx. -10dBs
signal to the LINE IN terminals.
3.
Adjust the recording level controls
until
the signal is available at
-8dBs at the LINE OUT terminals.
4. Adjust VR302 and VR402 until the
VU meters deflect to O.
Record 1kHz, 50Hz and 12.5kHz sig-
nals at an input level of OVU - 20dB.
Play back the tape.
Check to see that the 50Hz and
12.5kHz signal output deviations fall
within the standard range, using the
1kHz signal output as a reference. (It
is basically desirable
that the 1kHz,
50Hz and 12.5KHz signal outputs are
the same.
Adjust VR502 amd VR602 (for a nor-
mal tape), VR503 and VR603 (for a
chrome tape),
VR504 and VR604
(for a metal tape) until the indicated
deviation
of the 12.5kHz signal out-
put from the 1kHz signal output be-
comes
O.
Adjusting
point
VR701
801
VR702
802
VR302
402
For normal
tape:
VR502
602
For chrome
tape:
VR503
603
For Metal
tape:
VR504
604
-13 -
Standard
value
-8dBs
(0.3V)
Reference
frequency;
1kHz
0±2dB
at 10kHz
OVU
Reference
frequency;
1kHz
0±3dB
at 50Hz
0±3dB
at
12.5kHz
Ol
:s
Q)
<n
J
c:
0
C.
<n
Q)
er:
50Hz
Remarks
This
adjustment becomes necessary
when a change in playback level
results (for example, due
to head
replacement).
Perform
the adjustment when the
parts are replaced.
1. Bias current
adjustment for a
cassette deck should generally
be performed referring to the
record/playback frequency re-
sponse. This is because the fre-
quency response of a cassette
deck depends more greatly upon
the bias current than does that of
an open reel deck.
The current measuring
method
described below is an alternative
one.
2. If
the bias current is not properly
adjusted,
the record and play-
back characteristics become as
shown below.
Increase in high frequencies
Iwith a small bias current)
>t\
/1\' Optimum level
Decrease in
high frequencies
Iwith a larger bias current)
1kHz
12.5kHz
Frequency 1Hz)
No.4186

I(D-A77 A/B/C/E/J/U
Step
5
6
7
8
Item
Adjusting
recording
level
Checking
record/
playback
signal
distortion
Checking
signal
to
noise ratio
in recor-
ding/play-
back
Checking
erasing
coefficient
Adjustment
1.
Apply a 1kHz, approx. -10dBs
signal to the LINE IN terminals. Ad-
just the recording level controls
until the signal is available
at
-8dBs at the LINE OUT terminals.
2. After checking to see if the VU
meters
point to 0, record the signal
applied
to both left and right chan-
nels using a normal tape.
3. Play back the recorded part.
Perform the recording signal ad-
justment with VR501 and VR601
so
that the VU meters deflect to O.
1. Record a 1kHz signal so that OUT-
PUT level become -
8dBs and VU
meters
deflect to O.
2. Play back the recorded part. Check
the
output with a distortion meter
to see if the value conforms to the
standard value.
1. Record a 1kHz, OVU signal.
Stop the input by disconnecting
from the terminal to perform non-
signal recording.
2. Play back the recorded part.
Measure the OVU recording
output
and the non-signal recording out-
put for comparison using an elec-
tronic voltmeter.
Check to see if the value conforms
to the standard value.
1.
Apply a 1kHz signal to the LINE IN
terminals.
Adjust the recording level controls
until the VU meters
deflect to O.
2. Perform recording with the signal
enhanced
by 20dB.
3. Erase a part of the recording.
4. Measure the output difference bet-
ween the erased part and non-
erased part
to compare with an
electronic
voltmeter.
Adjusting Standard
point value
VR501 0 VU
601
Normal tape:
Less
than 2.5%
Cr02 tape:
Less
than 3%
Metal tape
Less
than 2%
Normal tape:
More
than 42dB
Chrome tape:
More than 42dB
More than 65dB
Remarks
The level
difference between left
and right channels for normal tape,
chrome tape and metal tape should
be less
than 1dB (1 VU). Perform the
adjustment using a normal tape,
level difference
between recording
and playback
for Cr02 and metal
tapes should be less
than 1. 5dB,
and
that between left and right
channels should also be less than
1dB.
Be sure to perform this adjustment
following bias current and recording
level adjustments.
Apply an output (- 72dBs) to the
MIC terminals with the recording
level controls set
to maximum so
that the VU meters deflect to O.
For the measuring, connect a band
pass
filter between the deck and the
electronic voltmeter.
/
Input
(1 kHz OVU
+20dBi
I rBand pass
I filter
Tape deckh
(recording
erasingi
Electronic I
voltmeter
Used test tape; Metal tape
9 Adjustment the Super ANRS circuit
(Super ANRS circuit for recording mode)
1. Remove the bias-cut connector on the main P.W. board to stop the bias oscillation.
2. Fully turn the semi-fixed resistors VRA01, B01 in the opposite direction of the arrow shown on the P.W. board.
(If
they have been roughly adjusted, there is no need to turn them.)
3. Set the MONITOR switch of the deck to SOURCE position with ANRS switch set to OFF.
4. Apply a 1kHz, -1 OdBs signal to the LINE IN terminals.
Adjust the INPUT LEVEL control until the output at test points, TP-L and TP-R are -5.5dBs. (Be sure not to
move the INPUT LEVEL control positions during this adjustment.) and then the OUTPUT level is approx. -5dBs.
(Corresponding
to + 3VU on the VU meters.)
5. Decrease the input signal to 40dB (its signal become - 50dBs) with an attenuator. (The output at the test point
is -45.5dB.)
6. Adjust the VRA01 (for left channel) and the VRB01 (for right channel) with ANRS switch set to ON until the out-
puts at the test points are -39.8dBs.
(The output difference is 5.7dB with ANRS switch set to ON from OFF.)
7. Check
to see if the output at test points is - 22dB ± 1dB with the input 5kHz, - 30dBs signal. (Its signal adjust
to 20dB with an attenuator.)
(The output difference with ANRS switch set to ON from OFF is 3.5dB ± 1dB)
-14 -

KD-A77 A!B!C!E!J!U
Step
Adjustment
8. Check to see if the test point output difference between that with ANRS switch set to ON and that set to OFF is
less than ±
O. 5dB, with the input a 1kHz, -1 OdBs signal. (its signal adjust to 20dB with an attenuator.)
9. Set ANRS
switch to SUPER from OFF when input 10kHz signal to LINE IN. Check LINE OUT level so that it
become from - 5.5dBs to -11. 5dBs ± 1dB.
(Super ANRS
circuit for playback mode)
10. Apply the Oscillation signal with connecting a condenser (1 JLF) to test points TP-L and TP-R for playback mode.
I
~ C:ndenser (~~~~)
OSC 8L-_---iAttenuator I ~ = ~~:=::=~ AN~r~uit
7'7 'TT
11. Fully turn the semi-fixed resistors VR703, 803 in the direction of the arrow shown on the P.W. board. (If they
have been roughly adjusted, there is no need to turn them.)
12. Set the deck to playback mode with ANRS switch set to OFF. (Use the non-tape cassette.)
13. Apply a 1kHz signal to the LINE IN terminals.
Adjust an attenuator until the LINE OUT levels become -5dBs. (This level is caliblation point.)
14. Adjust the input signal to 34.3dB with an attenuator, and then LINE OUT level become -39.3dBs.
15. Adjust the VR703 (for left channel) and the VR803 (for right channel) with ANRS switch set to ON until the
LINE OUT levels become -45dBs. (The output difference is 5.7dB with ANRS swith to ON from OFF.)
16. Apply 5kHz signal with the ANRS switch set to OFF.
Adjust an attenuator so that LINE OUT level become - 21. 5dB.
17. Check to see if the LINE OUT level is - 25dBs ± 1dB with ANRS switch set to ON from OFF.
18. Apply 1kHz signal of caliblation level with the ANRS switch set to ON fro,m OFF, check to see if the LINE OUT
level is less than -5dBs ±
O. 5dB.
19. Set the ANRS switch to SUPER, apply 10kHz signal to the LINE IN terminals.
Adjust an attenuator so that LINE OUT level become check to see if the LINE OUT level is -5dB ± 1dB with
ANRS switch set to OFF.
20. Play back the reference tape VTT-664 and check output level so that it less than ± 1dB when ANRS switch set
to ON from OFF.
21. To operate the bias oscillation, insert +B wire connector of the bias circuit.
Wiring Supplementary (refer to page 21 and 22)
-15-
O.M.F. Resistors
(R39 and R40)
No.4186

z
~
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~
00
Ol
Super ANRS Circuit
IC GOI TATOO0351- 01
~ 21 ~~~61
81 11 I
18
1
_evel ~~
IC 911
J
AdJ
UPC4558C
Boost Amp
LI NE IN
'Z~)'I
ANRS
I Switch
I
ON t oOFF
Input Se lect Super ANRS
CircUit
0;
MicroPhon~J SWitch
"Y---- 2SC1344 n
1 (E,F) I
le AOI TATOO0351-01
1
Control Switch
~--------,>UlO
.-
23
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Multi -Peak Le lA:! I Multi Peak Level
Indicator
EE
2 IC912
LBI416
Output Level
Control
Circuit
LINE OUT
~_ Head phone
UPC4557CI ?
Headphone Amp ,
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FF
REW
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REC
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REC
Mem
SHP
Switch
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xy Switch
-OFF -PLAY
i~~
I
1
Rec Proof SW
1
Play
Play Play
Play Solenoid
~j
I1IC2-1
IC3-1 ~~IC3-2
IC4-1
Play .1 Cassette
XI 2SC
Solenoid SW
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P:::~llri':k: ~
Pause
I1
IC2
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IC3-4 I X22SC C
To Amp
~~
58R31CCIj
Brake
I PLAY Vcc 16
Fast Deloy Fast
FF
Solenoid
2
15
IC2-6 ~y IC2-5 ~~ IC6-2j
~:IS4-~~ I
lc
3 STOP FF 14
X 2 C Brake
FF FAST -1162 Solenoid
4.. MErvo REW
13
~
Rew
5 REW PLAY
~ IC6-
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l"=- t--
6 PAUSE 11
Rec -
7 F't>lJSE 10
: IC2-4
REW REC
[g To
8 GND AR
~
Pause
Pause
Amp
H IC2-4 ~
Solenoid
..
X4
Pause I
2SC{~f
Solenoid
Counter Merrory
Fo" Sto~
ReelMotor Drive
HalllC
IC5-2 ~ ~IC6-1
IC5-1
X6,XI12SC456R3(CO
L--
1~~C458
~
Xl, X9)2SD468 (B,C)
[fel
-PGlal)
Play Stop
XIO
~ Motor
r-i
IC6
-4 ~
X 8 2SC 1162 (B,C)
4'""' ~
Start
011
RD62E
IC5-4 J-r1'C5-3
F To Amp I
I
~wer Supply Circuit
'v
5V To Mecha Cor
To LED
nlC;lf; 17
IXB 2SA 715 (B.C) I ?III
AC
To Amp
IC I M54410P
IC 2 HD7404P
IC 3 HD7400P
IC4 HD7400P
IC5
HD7400P
IC6 HD7403P
pstan
Motor
rol
s:
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n
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Cl
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m
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--
C

KO-A77 A/B/C/E/ J/U
Integrant Circuit
IC A01, B01
G01,H01
TAT000351-01 Super ANRS cirucit IC C01
J01
(Top view)
242'" 222'2'C"g 18 '7 '6 !~.4·3
Lnnnnn
)
aSuPt'rA~~F<S
w u U I U L.J
I 2 3 4 ~ 6 7 8 9 10 I' 12
(Top view)
AM PlIFIER No 2
,---- _-,--I __
NON
OUT INV
Vc,, PUT INPUT
8 6 5
UPC4558C ANRS control amp. circuit
Equivalent circuit (1/2)
Vcc+O--~-~-~""",-",-,
INV
INPU'r
NON -INV o--t--t--i-
INPUT
~
Y.-+~OUT PUT
IC901 UPC4557C Headpone amp.
Top
view is the same as
UPC4558C.
IC903 LB1416
Multi-peak level circuit
(Top view)
OUT 05 04 03 02
~[] Q I11
() ~( LB 1416
~-~3~ATTO"'~~
IN IN IN Ro Vret Ro GNO
(Mecha. control)
OUT NOr-. Vec
pu, INV
iNPUT
'------- ,,---~
AM PLIf'IER No I
Equivalent circuit is the same as UPC4558C except R8 only.
Equivalent
circuit
OUT GNO
05
04 03 02
IC1 M54410P See the service manual of KO-85A/B/C/E/J/U (No. 4165 -page 7).
No.4186
IC3,4,5 HP7400P
(Top view)
IC2
14 vcc
lJ r
Equivalent circuit (1/4)
.----~---r----o .'cr
130
y
L-.,~ _____ -+- ____ --<> CND
H07404P 1
H07403P f See the service manual of KO-A7 A/B/C/E/J/U (No. 4185 -page 17)
IC6
-18-
01

KD-A77A/B/C/E/J/U
Standard Schematic Diagram of KD-A 77 (Amplifier circuit)
A
B
c
D
E
F
G
L - C H
R- CH
L I NE
OJT
1 N
I
, VMWI528
RI02
33K
RI04
rSOK
18K
2
X 701
2SC 1344(E,F)
7.3 R96f rSK
IC911
UPC4558C
3
X702
2SC458PG(C,O)
Roh
4
PB EQ.Adj.
0911
., INPUTLEVEL _Input Level Control
(_...w'::':"T <WE"A3A-054F (on the front panel)
TAT0003SI-OI
5
ANRS Adj
XGO I
2SD468(B,C)
6
IC JOI
UPC4558C
7
X301
2 SC458A (c,O)
Meter G
8
X 911
2SA 844 (C;ol
A from
MECHA CON
c
X912
2SC458PGCC,O)
9
X303
2SD468/a,C)
-
le 912
Roh
eN-AS
L
rr~~~~~~*RAI~5 ~~~~~~~~~~X~7--
[gJ
~
2
X~2 X SOl
2SC458PG(CPJ 250468 (B,C)
8-{J---.'W'-+t:
;;
~
,.
~
NOTE
Recording Level Adj.
X904
2 5C458 PG(C,O)
IC~2
UPQ4066C
470 25D468(I:\C)
XS02 XS03
2SCI344(E,F) 2SC 458 (C,O) Output Level
Adj.
(on the front panel)
VSK5D24-211
- eN AZ
R915 rOK X905,XOO6
2SC 1685(S}
REC HEAD
VGH0425 -3QI-OA
R 1/2 CN-A 3 ERASE HEAD
R75
270
10
I METAL
er 0"
I SUPER
.J
ANRS
from MECHA CON I§]
CN- A4
-2
1-7
076,77
SL8-26URIN
075,78
SLB-26GGIN
ALL VOLTAGES ARE MEASURED BY YTYM WITHOUT I NPUT SIGNAL AT STOP MODE - Diode-
- Transistor-
;~ cMM0904I4-0A
I 2 Automatic CrOzSelect P. W B
f[iiiJl (M_NORM)
UNLESS OTHERWISE SPECifiED ALL RESISTORS ARE 1/4 W,:t 5% CARBON FlESISTORS
AND ALL CAPACITORS ARE 50Y FIXED CERAMIC CAPACITORS OR SOY MYLAR CAPACITORS u
~ QSPOO29-001
b1w~d
UF UNFLAMABLE CARBON RESISTOR
'MF METAL FILM RESISTOR
t:wIF OXIDED METAL
FILM RESISTOR
\_LL !:20% LON LEAK CURRENT ELECTROLYTIC CAPACITOR
P.P POLYPROPYLENE CAPACITOR Blue line
shows the signal at playback.
LN LOW NOISE CARBON RESISTOR Red line
shows the signal at recording and + B circuits.
parts are safety assurance parts. When replacing those parts, make sure to use the specified one.
,PS POLYSTYRENE CAPACITOR
'Ta TANTALUM SOLID ELECTROLYTIC CAPACITOR
-19 -
No.4186

KO-An A/B/C/E/J/U
Standard Schematic Diagram of KD-A 77
(Mecha. control circuit)
A
B
c
D
E
F
G
REMOTE CONECTQR
OMC 0888 -008
- Diode
CN-5
2
r
01005
To Amp §1
CN-B
01
tA~Et-~~~J--+~
REC
01003
o 5
01006
FF
IREW
01007
CN-9
8 IPLAY
STOP
IFF
5 fEW
4 "'~
4
31"EC
o 2
REC
liE
VSTO~OOI:J
CONTROl SW ASS'Y
TIMER SW
C REC~6~l!O~~~O;)
rv:W4~
-
riMER sw PW B I 0
L
I
r-
CN-8
I 4 •
I 6
I
N-
CN-5
3A
lA
2A
3
53
44 RI5270
4 RIG 270
52
RI? 330
@
!f
-g
44 R44 270
'"''
44 R45270
Cl
0.001
C2 oml
C3
C4 0001
C5 0001
C6
0001
07 IN34A
DB
09
IN34A
IN34A
r- ;:.. -, I
Ir o~ ____ _
3 8
ME~ORY
sw pws
I:
28
4
R36 100 <NI ~
IC I
M 54410P
"
C23 IOtll6V
5
--
IC2 HD7404P
IC 2
PLAY
IC3 H0740QP
IC 3
D61N34A
R23
IK
6
R26
56
+C 16
looop
63V
02
152076
7
IC4 HD7400P
03) RB
IN34A IK
X7
2SD468(B,C)
RIO
4,7K
X8
2SC 1162 (B,C)
8
XI
2SCII62(B,C)
R4
270
To Amp
A 8 E
I!
.rl .-t~I~---{~--------------------------------r--------------t----------------t---~-----x~s--------------~2~SC~~8~ X9
v _ 2SC45BPG(C,O) (C,DJ 250468 (8,C) '-------------------------H-t---"
9
I
,
t
I"
·32
126
30
• 27
126
125
I
19
,I!"
• 18
278 I 12
1 "
~W4~ .J ~================================================================~+=t===~
~~~~ftRS~~~8ME~Coorn~8L~ ~--------------------------------------------~X~D~----~X~I~I-----X=12~----+H---------+~-+~~
CN-M4
4
CN-M3
4
CN-M2
PL3
CN-MI
MEMORY sw
0852301-101
(STOP- OFF-PLAY)
- - - - .. 2SD468(B,C) 25C458PG 2SC458PG.(C_",,0'-l) H-t------+--' I ToAmp rrg
(e,O) r
F To Amp I 53 ~'o~~
L!" 022
I
IOEI
'F'Jld)~77/C/Ji-/U"--'==~ ____ H
97 :
10
Ni j:::::".
QSPOO29-001
L _ J '~:;;;:::,
'-VM=S
HOLE IC PW B
IH
PL I
I m 1606-00A
~711
1J.l50V
.,.
lOjJ H
DM603
IOEI-8
~MW~9 ~ vGP0201-005
TERMINAL ,P'NB
I TISA
98
~ ~ '~""'I' RESISTOR PW B
0: 31
PW B
L
F2(KD-A77/C/J/U wlthou1F2}
- --
XI4
2SC 458PG (C,D)
XIS
2SC 458PG (C,D) _...1
- Transistor-
NOTE
No.4186
-- 20-
ALL VOLTAGES ARE MEASURED BY VTVM WITHOUT INPUT SIGNAL AT STOP MODE
UNLESS OTHERWISE SPECIFIED ALL RESISTORS ARE 1/4W.t5% CARBON RESISTORS
AND
ALL CAPACITORS ARE SOV FIXEO CERAMIC CAPACITORS OR 50V MYLAR CAPACITORS
,UF UNFLAMABLE CARBCtIi RESISTOR
MF METAL FILM RESISTOR
{)M7 0 XIDEO METAL FILM RESISTOR
1_1." !20% LOW LEAK CURRENT ELECTROLYTIC CAPACITOR
PP) POlYPRQPYLENE CAPACITOR
,PS; POLYSTYRENE CAPACITOR
"T_(v TANTAUJM SOLID ELECTROLYTIC CAPACITOR
"I,.~_ lOW NOISE CARBON RESISTOR
Red lines show +B circuits.
parts are safety assurance parts. When replacing those parts,
make sure to use the specified one.