JVC D-M3 - Page 11

D-M3 A/B/C/E/J/U
[III] Electrical adjustment location
Main Amp. P.W. Board (parts ass’y side view)
(Turning in the direction the arrow increases the levels)
vR102 /
[>
L
Playback
equalizer
A
adj.
VR202
[>-R
veR201 VR101
—.
Recording level adj. R A U a
RL
VR252 VR
= VR151 Playback level
adj.
Bias current
adj.
VRI52. VRIS3
Front
Fig. 18
[IV] Electrical circuit adjustment procedure
In the steps maked by an asterisk (*), adjustment should be Adjustment should be performed in the order of steps 1, 2,
performed, however, only checking is sufficient with steps 3,... Perform this adjustment with the NR switch set to
other than those. OFF.
Adjusting Standard Beavers
point value
Adjusting . Play back the OA-L212 Reference tape This adjustment becomes necessary
playback (1 kHz) with the tape select switch set 201 (0.3 V) when a change in playback level results
level to the SF/NORM position. (for example, due to head replacement).
2. Adjust VR101 and VR201 until the
LINE OUT becomes about —8 dBs.
(When using the OA-L211 reference
tape, LINE OUT levels become
— 13 dBs.)
2*
|
Checking
1
.(Metal
tape
—2.4
cm/s)
VR153
Reference
This
checking
should
be
performed
for
record/
Record
1
kHz,
50Hz
and
12.5
kHz
253
frequency;
normal
tape
and
for
both
right
and
left
playback
signals
at
an
input
level
of
OdB
to}
(Metal)
1
kHz
channels.
frequency
—
20
cB.
1.
Bias
current
adjustment
for
a
micro
response
Play
back
the
tape.
VR152
0+3
dB
cassette
deck
should
generally
be
Check
to
see
that
the
50
Hz
and
252
at
50
Hz
performed
referring
to
the
record/
12.5
kHz
signal
output
deviations
fall
|
(Normal)
playback
frequency
response.
This
is
within
the
standard
range,
using
the
0+4
dB
because
the
frequency
response
of
a
1
kHz
signal
output
as
a
reference.
at
12.5
kHz
cassette
deck
depends
more
greatly
2
.{(Normal
tape
—
2.4
cm/s)
(Metal)
upon
the
bias
current
than
does
that
Record
1
kHz,
50
Hz
and
8
kHz
signals
of
an
open
reel
deck.
The
current
in
the
same
manner
as
in
the
above.
0+4
dB
measuring
method
described
left
is
Playback
the
tape.
Check
the
same
at
8
kHz
an alternative
one.
manner
as
in
the
above.
(Normal)
2.
If
the
bias
current
is
not
properly
ad-
justed,
the
record
and
playback
Increase
in
high
frequencies
characteristics
become
as
shown
(with
a small
bias
current)
left.
$s
Es
2
Optimum
level
a
2
Decrease
in
high
frequencies
(with
a
larger
bias
current)
50
Hz
1 kHz
12.5
kHz
Frequency (Hz)
a |
= No. 4213