Dokorder 7700 - Page 19

2-5
LEVEL
METER
CALIBRATION
a. Specification
0 dB
of the
level
meter scale.
b. Adjustment
Adjust
the
semi-fixed
resistors
VR-108
and
VR-208'
c.
Reference
Refer
to
Fig.6-1.
d.
Test
tape,
special
tools
and
instruments
required
Signal
generator and
VTVM.
e. Test
point
Connect
the
VTVM
to the
line
output
jacks.
f
.
Mode
of
switch
(1)
Monitor
SW-SOU
RCE.
(2)
P.B.
level
controls-MAx,
Record
level
controls-MAX'
g.
Procedure
(1)
Connect
the
signal
generator
to
the
line
input
jacks,
and
apply
a
7OO
Hz signal
of
-20
dB
to the
line
i n
puts.
(2)
After
the
above
connection
is completed,
adjust
the
semi-fixed
resistors
VR-108
and
VR-208
on the
AMP
pC
Board
(pCM-446),
so
that,
when
the
line
output
level
is
0
dB
10.5
dB, the
level
meter
mav
indicate
0
dB.
h. Note
Since
the
level
meter
may
give
an
incorrect
reading
when
the
tape
deck
is
placed
horizontally
or
in a
slanted
position, be sure
to
undertake
the
adjustment
with the
tape
deck
placed
vertically'
2.6
BIAS
FREOUENCY
Specif
ication
130
KHz
11
KHz
Adjustment
Adjust
the oscillator
coil
L-40'l
(1139).
Reference
Refer
to
Fig. 6
1.
d. Test
tape,
special
tools
and
instruments
required
Frequency
counter
e.
Test
point
Connect
the
frequency
counter
across
the
test
points
TP-4 and
TP-5'
f
.
Mode
of
switch
(1)
Record
SW-ON
(button
in).
(2)
P.B. level
controls-MlN,
Record
level
controls-MlN'
g.
Procedure
(
1
)
After
the
above
connection
is completed,
load
the
blank
tape
on the
deck
and
push
the
record
button
and
play
button
simultaneously
to
enter
the
record
mode,
then
push
the
pause
button
to
stop
tape
travel'
(2)
Adjust
the
bias
oscillator
coil
L-401
on
the
Bias
PC Board
(PCM-413),
so
that
the
bias
oscillator
frequency
may
be
130
KHz
11
KHz.
h. Note
Connect
the
O lead
of
the
frequency
counter
to the
test
point
TP-4,
and its
O lead to
the test
point
TP-S.
b
b
a.
16