JVC CD-1770 User manual

MODEL
CD-1770/A/B/C/E
STEREO CASSETTE DECK
No. 4144
May 1976

Contents
Page
Specifications ........ 0.2... ccc ccc 2
F@atu res cannes cese dere: a eta eae aeeeg aeie we ecwree ea Beas 3
Controls and Connections ............0000000e008 3
Main Parts Removing..............2000eeeeeees 4
Enclosure Assembly ..........000cc ce eeeeues 4
Electrical Parts 2.5.02. ic uiweeeke dew en's 6 5
Mechanical Parts ..............0000 cece eeees 6
Main Adjustments ........... 2.00 c eee eee eens 7
Trouble Shooting Guide .............. 00 eee eeee 12
Maintenance .......... 2... cc cece eee eee ees 13
Block Diagram... 0.2... ... ccc eee eens 14
Specifications
Type Stereo cassette deck
Track system 4-track, 2-channel
Cassettes C-30, C-60, C-90
Frequency response :
Signal-to-Noise ratio :
Effect of Super
ANRS
Improvement of
S/N :
Improvement of fre-
quency response :
Imrpovement of
distortion
Wow and flutter
Crosstalk
Harmonic distortion :
Bias z
Chrome *1 20 — 18,000Hz
(Nominal)
30 — 16,000Hz
(Typical)
Regular *2 20 — 17,000Hz
(Nominal)
30 — 15,000Hz
(Typical)
Supasses DIN 45500
*1 TP-18 or Equivalent
*2 QP-12 or Equivalent
56dB(JIS) The S/N is improved by
5dB at 1kHz and by
10dB above 5kHz with
ANRS on
62dB with ANRS
(DIN45500 weighted)
(normal tape)
the same as with ANRS
OVU recording; 6dB at 10kHz
+5VU recording; 12dB at 10kHz
OVU recording; 3% less at 10kHz
0.05% (WRMS)
0.18% (DIN45500)
65dB
1.2% (normal tape)
AC bias (95kHz)
Page
Wiring S622 Hit eta bt aioe Se aie te 15
Standard Schematic Diagram...............20005 16
Circuit Board Parts ............02 cece eee eeeee 18
Main Amp Circuit Board. ........... 0000 cca ee 18
ANRS Circuit Board ...............00000euee 22
Switch Circuit Board .......... 00000 e ences 24
Mechanical Component ..............00000eeeas 26
Enclosure Ass’y and Electrical Parts
except Circuit Board Parts .............0.0000. 32
ACCOSSOFICS 65 a oie cisie-bhe aWewcs ainate o Pree che ates 34
Pack ing 220i esavaretag ates GA ato iis Ge ahs Ae a 35
Erasure AC erasure
Heads Recording/playback
Motor
Tape speed
Recording time
Fast forward time
Rewind time
Semiconductors
Input jacks
Output jacks
Power requirement
Power consumption :
= Sen-Alloy head
Erasure = Ferrite head
Frequency control DC servomotor
4.8cm/sec
2 x 30 minutes with C-60 cassette
75sec with C-60 cassette
75sec with C-60 cassette
6 ICs
40 transistors
2 SCR and 30 diodes
MIC jack x 2
Max. sensitivity 0.2mV
Matching impedance 6002
Input jack x 2
Min, input level 78mV
Input impedance 1002
Output jack x 2
Output level 0~ 0.5V
Output impedance 10k
Matching load impedance 6.8ka
or more
Headphone jack x 1
Output level 0.3mV
Matching impedance 6.8k9 or more
AC 120V, 60Hz (CD-1770/C)
AC 240V, 50Hz (CD-1770A/B)
AC 220V, 50Hz (CD-1770E)
30W
Dimensions Width 16-1/2"' (420mm)
Height 3-1/2’ ( 88mm)
Depth 10-7/8”" (277mm)
Weight 12.1 Ibs (5.5 kg)
Design and specifications are subject to change without notice.
CD-1770/A/B/C/E a ee m
No. 4144

Features
SEN-ALLOY head. Mixing facility.
Built-in ANRS (U.S. Pat. 375 7254 and 376 9612) and Wow flutter show high class mechanism.
Super
ANRS.
Frequency
controlled
servomotor.
Multi-point
peak
level
indicators.
Full
auto-stop.
Timer recording and playback. Tape amount indicator.
Controls and Connections
COS)
@ ©
®
DM OM DDBDAOM ®
Fig. 1
Fig. 2
Left-[L]
1
Left
channel
tevel
meter
[LEFT]
19
MIC-REC
{evel
controls
[MIC/DIN]
(
2:
ht-[R]
2
PEAK
level
indicators
oats
3.
Right
channel
level
meter
[RIGHT]
20
~LINE-REC
level
controls
[LINE]
(
Right-[R]
:
me
indicator
sires
21
Memory
counter
with
reset
button
[COUNTER]
S
indicator
[ANRS]
22
Playback
level
control
6
Super
ANRS
indicator
23.
REC
button
:
ees
aus
rae
24
REW
button
[REW
<<
]
Sheet
25
Playback
button
[PLAY/REC
>
]
We
rece
iit
26
Fast
forward
button
[FF
PP
]
e
Lie.
a
Rica
27.
STOP
button
[STOP
@
]
bes
a
pene
me
28
Pause
button
[PAUSE
4
|
13
Left
channel
microphone
jack
[MIC-L]
29
Right
channel
LINE
OUT
ferninal
:
3
:
30.
~—_
Left
channel
LINE
OUT
terminal
14 ~~ Right channel microphone jack [MIC-R]
15
Headphone
jack
[PHONES]
31.
DIN
socket
[REC/PB]
16
Bena
oe
Si
32
Right
channel
LINE
IN
terminal
ae
33
Left
channel
LINE
IN
terminal
17
ANRS
switch
34
Memory
switch
18
Super
ANRS
switch
z
CD-1770/A/B/C/E
i Rts No. 4144

Main Parts Removing
This
cassette
deck
which
features
a
compact
design
and
high
performance
uses
minuature-sized
parts
which
are
closely
arranged.
Use
special
care
when servicing
it.
Enclosure Assembly
Arrow is shown procedure to
Insert and push remove the cassette lid.
in 4 holes by
small stick. ar
& wer TAC, Cassette *@)
Power switch
knob
Cassette door 1, Press the eject button, then the
cassette door loading upward.
2. Remove the cassette door by pressing
it under side.
Slide volume knobs Pull off it upward.
4Power switch knob
the bracket.
4Eject knob
. Remove the rope on eject knob.
4Select knobs . Remove 2 screws fastening the switch @)
C. board. (EQ & BIAS)
. Remove SW. C. board with it’s
bracket.
. Pull out the select knobs to outer or
inner of the top cabinet.
Remove 6 screws fastening the top cabi-
net, after removing the head cover,
cassette door, botton cover and wood
CD-1770/A/B/C/E
No. 4144 ar oe
e It canbe removed for it’s cleaning
or replacing with other parts un-
removing.
e When replace the cassette door,
insert by pressing it under side,
then one or other side of cassette
door by full locked.
When remove the bottom cover, can
be removed the wood cabinet at as
same.
After removing the bottom cover
only, can be adjusted semi-fixed
resistors (VU meter gain, peak level
and playback gain) on main amp
C. board.
Remove 6 screws fastening the bottom
cover.
When replace the knob, insert knobs
guide plate in score hole of top cabi-
Insert and push in 4 holes near the
power switch by small stick, then can
be removed off the power switch knob.
1. Remove 1 tapping screw fastening
2 earth lugs can be removed as same
the front panel.
cabinet.

Note:
When you remove or replace the cassette lid, be careful not to scratch A position on the front panel.
1. To remove
You have to pull out the cassette lid at direction (2)
pushing down it at direction
scratch on the front panel (A) by your fingers.
2. To replace
@)and controling for not
Fig. 4
At the first, have the cassette lid as same way to
remove. Next, insert holder of it as equal right and left
sides.
At the same time, control for not scratch as same way to
remove, and push in to locking the cassette lid.
(The first push in left side, next, right side.)
not full opening
gv
2 Bae
half opening
2)
When you remove the cassette lid,
open at half mode.
CD-1770/A/B/C/E
No. 4144

Electrical Parts
ANRS C. board
Power switch
Slide volume
Fig. 5
Remove electrical parts after removing the bottom cover.
Main amp Remove 3 tapping screws fastening the
circuit board ass’y main amp circuit board.
ANRS circuit board Remove 2 screws fastening the ANRS Q)
ass’y C. board
Switch circuit board 1. Remove 2 tapping screws fastening Remove switch circuit board ass’y
ass'y the bracket for switch C. board ass’y. after removing the bracket for it.
2. Remove 4 screws fastening the Bias
SW C. board (2 p.c.s) and the EQ SW
C. board (2p.c.s)
©
. Remove 2 screws fastening the trans.
bracket.
2. Remove 2 screws fastening the trans-
former
3. Disconnect it’s wires.
Power transformer
Remove the Mic jacks ass’y after remov-
ing the front panel.
Remove 1 screw fastening the Mic jacks
ass'y.
Mic jacks ass’y
Remove the front panel and the main
amp C. board ass’y.
MIC/DIN level controls..... 4screws
LINE level controls........... 4screws
Playback level control ..... 2screws
Slide level controls
CD-1770/A/B/C/E
No. 4144 GS

Mechanical Parts
Motor circuit board Motor @) @ Motor Capstan belt
tA t
rs it =
= lp
te}
°
fe}
Take up disc
= 0
ce}
ra
©
CSM
i
vi
©
=A
arm ass'y ol
Be careful not to stain the belt.
When replace the motor, replace it’s
circuit board as same time.
Be careful no to stain the belt.
When replace the flywheel, don’t
forget to insert a nylon washer to
it’s shaft.
Fig. 6
Mecha-ass’y Remove the cassette cover, head cover
and bottom cover. @
chassis.
Motor . Remove the take up belt.
. Remove the capstan belt.
. Disconnect 2 wires of motor circuit
board ass’y.
. Remove 3 screws and 3 washers fasten- Q)
ing the motor.
Pinch roller arm assy 1. Remove “E” ring holding the pinch @)
roller arm ass’y.
Take up disc . Remove the counter belt.
. Remove “E” ring holding the take up
disc.
. Pull off the disc from the shaft.
Supply disc 1. Remove “E” ring holding the supply 6)
2. Pull off the disc from the shaft.
Remove 4 screws fastening the macha-
Flywheel . Remove the take up belt.
. Remove the capstan belt.
. Remove 2 screws fastening the fly-
wheel holder.
. Pull off the flywheel.
. Remove spring on the arm ass’y.
disc.
NOTE; Don't dirty, slippery and undue run-out the capstan belt and counter belt.
CD-1770/A/H/C/E
ay a No. 4144

Main Adjustments
Electrical Adjustment
Equipment and measuring instruments used for adjustment. AUDIO Freq. OSC
1.
V.T.V.M.
(measuring
AC
in
millivolt)
N
cas
ATTENUATOR
2. Audio-frequency oscillator | Jeep)
(range: 50—20kHz and output OdB with impedance 60022) ae By aS, i 60002
DVO"
3. Attenuator BOIS:
4. Reference tapes for REC/PB pease
TS-1 (OP-12, C521V) — normal tape by @
TS-2 (TP-18, C401R) — chrome tape ouTPUT LINE IN
5. Reference tapes for playback
VTT-664 (1kHz 16mM)
VTT-666 (400Hz 22mM)
6. Resistors
1002 (for measurement of the bias current)
6002 (for attenuator matching)
INPUT
LINE OUT
Fig. 7
When you adjust following item, we recommend to you to keep doing step No.
CA
1 Level meter . Set the deck in the record mode. (Main amp The angle of meter deflection
Input 1KHz signals (about 10dBs) from C. board has been factory adjusted, but
LINE IN jacks and adjust LINE IN TAA313201) should be adjusted when parts
volume control so that LINE OUT are are replaced.
-8dBs.
3. Adjust semi-fixed resistors R146 and VR103,203 When adjust the level meter,
246 in this condition it obtain zero don’t use a headphone.
VU meter reading.
2 Peak level
. Set as same mode at step(1) and adjust (Main amp
semi-fixed resistor R506 so that the C. board
“0” indicator is lighting and no light- TAA313201)
ing at -1dB from step(1) with atten- R506
uator.
2. Adjust semi-fixed resistor R508 so that
the ‘’-5” indicator is lighting at -5dB
from step(1) with attenuator.
3. Adjust semi-fixed resistor R510 so that
the ““-10” indicator is lighting at -10dB
from step(1) with attenuator and no
lighting at -11dB from step(1) with
attenuator.
4. Adjust semi-fixed resistor R504 so that
the “+3” indicator is lighting at +3dB
from step(1) and no lighting at +2dB
from step(1) with attenuator.
5. Adjust semi-fixed resistor R502 so that
the “+6” indicator is lighting at +5dB
from step(1) with attenuator.
3 Playback . Set equalizer switch at normal and (Main amp . Adjust playback sensitivity
sensitivity playback reference tape VT T-664. C. board) when heads are replaced.
Adjust semi-fixed resistors R115(L) R115,215 2. Make this adjustment after
making sure level meter
deflection angle is correct.
and R215(R) so that level meters indi-
cate zero VU (about 0.3V at LINE
OUT).
2. Playback reference tape VTT-666 and
check that the VU meter indicate CAL.
CD-1770/A/B/C/E
No. 4144 2ghe

4 Bias
current
1. Adjust bias current when
heads or other parts are
replaced.
2. Use the highclass V.T.V.M.
for high frequency re-
sponse.
3. After the bias current
adjustment, check the fre-
quency response at 10kHz
signals.
(Main amp
C. board)
1.
Insert
a
1002
resistor
into
the
ground
side
wiring
of
the
head
and
connect
the
V.T.V.M.
across
the
resistor,
and
set
the
BIAS
SW
at
chrome
or
normal.
First
adjust
for
chrome
tape,
then
for
normal
tape.
2.
After
the
deck
correct
the
head
wires,
input
the
standard
level
of
1kHz
sig-
nals
to
use
reference
tape,
and
measure
REC/PB
frequency
response
at
10kHz.
3. Adjust semi-fixed resistors R604,704
(chrome) 605,705(normal) so that the
10kHz frequency response does be-
chrome
come
+10dBs.
R604
,704
Repeat
the
recording
and
playback
so
normal
that
10kHz
signals
become
correct
fre-
R605,705
quency response.
Level over at 10kHz compared with
1kHz — bias current less
Level less at 10kHz compared with
1kHz — bias current over
5
Recording
1.
Set
the
deck
in
the
record
mode.
(Main
amp
.
This
adjustment
is
necessa-
signal
2.
Input
the
1kHz
(-—10dBs)signals
to
C.
board)
ry
when
heads
are
replaced.
current
LINE
IN
jacks
and
adjust
the
recording
2.
Make
this
adjustment
after
level control so that the VU meters
adjusting steps(1) through
indicate
zero
VU.
(4)
3.
Playback
the
tape,
adjust
the
semi-fixed
chrome
3.
Check
the
frequency
re-
resistors
R606,706(chrome)
R607,707
R606,706
sponse
at
10kHz
after
this
(normal)
so
that
the
VU
meters
indi-
normal
adjustment.
cate
zero
VU.
R607,707
4.
Set
EO
and
BIAS
switches
according to type of tape
used.
R324 ,424
(REC
GAIN)
R338,438
(DC
BIAS)
R325,425
(CONT
GAIN)
R312,412
(PB GAIN)
6
ANRS
.
Disconnect
'‘D”’
connector
of
bias
oscil-
circuit
lator
so
that
oscillator
does
not
operate.
2. Set the deck in the record mode.
3. Input 1kHz —10dBs signals from LINE
IN jacks adjust the recording volume
controls so that the voltage across
LINE OUT is —5dBs.
4. Turn R325 and R425 (CONT GAIN)
and R338 and R438 (DC BIAS) in the
direction opposite to the marking.
5. Adjust R324 and R424 so that level
does not change when ANRS is turned
on and off, and turn on ANRS.
6. Input 1kHz, —50dBs signals from
LINE IN.
Adjust R338 and R438 so that voltage
across LINE OUT is —-39.5dBs.
7. Input 5kHz —30dBs signals from
LINE IN.
Adjust R325 and R425 so that voltage
across LINE OUT is —21.5dBs.
8. Repeat steps(5) through (7).
9. Turn ANRS switch is “Super” position
when input 10kHz -10dBs signals from
LINE IN.
Check output levels are -11dBs +2dB.
10. Connect receptable of bias oscillator
disconnected in step (1).
11. Play reference tape VTT-664 and adjust
R312 and R412 so that level does not
change when ANRS is turned on and off.
CD-1770/A/B/C/E
No. 4144

Mechanical Adjustment and Repairs
a
REC/PB head 1. Turn the adjustment screws ((A)and screws If either of the record/play-
(Azimuth ) so that measure ‘’a” is 3.5mm. back head and the erase head
inclination) 2. Insert screws in the spring and shown low performance be-
unfasten it on the head panel. cause of wear, broken wire of
3. Fasten the screw(D) on the head excessive magnetization, it
panel. should be replaced.
4. Fasten the screw (C). If necessary, adjust playback
5. Turn the adjustment screw(D)so that sensitivity, REC bias current,
the head is horizontal. and bias trap.
6. Playback the test tape C-120 (front (Screw (A) and(B) are head
cutted cassette) and turn the adjust- inclination adjustment.
ment screws ().6) and(D) so that Screw is head azimuth
the test tape move running to no adjustment.
touch the tape guide tip (upper or Screw(C)is fixed.)
under side). If checking is difficult, cut
1)When the test tape uncorrect touch- front upper side (near E head,
ing at upper side of tape guide, REC/PB head and capstan) of
loose the adjustment screws and the cassette C-120 by a cutter
to move the head position at knife, etc, then easy check it.
under side.
2)When the test tape uncorrect touch-
ing at under side of tape guide
fasten the adjustment screws (A)and
(B)to move the head position at
upper side.
7. Insert the cord plug into the LINE
OUT jack (or REC/PB), and connect
the other end of the cord to a
V.T.V.M. (vacuum tube voltmeter}.
8. Play the azimuth adjustment test tape
(e.g. JVC’s VTT-653, 10kHz).
9. Turn the azimuth screw so that
the output will become maximum.
10. If output of left and right channels
unbalance level, turn the adjustment
screws (A) and for correct the head
Position.
1) If output of right_channel less level
loose the screw and fasten the
screw(B).
2) If output of left channel less level,
fasten the screw and loose the
screw(B).
11. After this adjustment, the screw(B)
should be locked with a bond.
head panel
tape guide
—=— (upper side)
tape
tape
tape guide
(under side)
<_
After replacement, adjust the
head height position.
Playback the test tape C-120 (front
cutted cassette), and turn the adjust-
ment screw so that the test tape
move running to no touch the tape
guide tip (up or under side).
1)When the test tape uncorrect touch-
ing, at under side of tape guide, loose
the screw ;
2)When the test tape uncorrect touch-
ing, at under side of tape guide, fasten
screw (F).
Erasing head
(height)
tape guide
~=—(upper side)
tape
tape
el tape guide
(under side)
CD-1770/A/B/C/E
No. 4144 — 10 —