JVC CD-1770 Service Manual

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

JVC CD-1770 Specifications

General

Brand	JVC
Model	CD-1770
Category	Cassette Player
Language	English