Dual C 822 Serviceanleitung Seite 7

r
DUAL
C
822-electrical alignemnt
Necessary instruments and tost cassett€s
2 millivoltmeters
AF oscillator
oscilloscope
frequency counter
test cassette
4OO
Hz
-
20
dB,
l0
kHz
-
20 dB
test cassette
400
Hz
Dolby
level
2oo mwb/m
test
cassette
Cr reference medium section
(e. g. BASF
chrome
dioxide,
C 60)
.1
test cassette Fe
reference medium section
(e.
g. BASF
super
LH,
C
6O)
1
test
cassette
Fe-Cr reference medium section
(e. g. Sony
Fe Cr Duad,
C
60)
.i
test
cassette
metal reference medium section
(e.
g.
Scotch Metafine
C
46)
.
General notes
The magnetic
head
and
all ferrous
components
which
come
into
contact
with the tape must be magnetized.
Readjustment must
be
carried
out
in
the
sequence
stated.
The L
101
and L
101
'
multiplex
f
ilters are set
precisely at the factory
and must
not
be
readjusted.
Playback
Magn€tic head adjustment
Remove the
screws 11
on the
f
ront trimplate.
Remove the cassette
com-
partment frame by
presslng
it
in at the side, insert the test cassette
(sec-
tion determined
for
gop
adjustment)
10 kHz
-20
dB.
Connect
the millivoltmeters
to
outputs L and
R (cinch connectors
).lf
only one
millivoltmeter
is
available, switch
the outputs in
parallel.
Fe,
)
Using
the adjustment screw
to the left of the
magnetic head, adjust
for
maximum voltage.
After
alignment.
lock the adjusting screw
in position
using locking com
pound.
Note:
lf the outputs
are
arranged in paral
lel,
secondary
peaks
wi
ll
occur. ln this
case,
adjust
for the
main
peak.
The difference between channel L and channel
R
at
1O
kHz
(S
aA.
Playback
level
lnsert
test cassette,400 Hz
Dolby
level
Fe,
Dolby:
On, MPX:
Off
,
ln each
case,
set
580 mV
+
0.25
dB
for track
1 using
VR 103 at cinch
output
L
for track 2
using
VR
1
03'at
cinch
output
R
Playback
frequency
lnsert test cassette, 400 Hz
-
20 dB, 10 kHz
-
20
dB
Fe, {Dolby: Off
,
MPX:
Off
)
}
Both
level components
of
the
test
cassette
should
have
the
same
output
voltage
at outputs
L
and
R-
lf
a voltage rise
is
determined in
the
case
of
the
10
kHz-20d8
level
in
relationtothe40OHz-20dB
level ,connec-
tions J
1
and
J
2 or J 1'and
J
2'
must be
disconnected.
lf
the
10
k{z
-
2O
dB level is lower than the 400 Hz
-
20
dB
level
,
connections J
'1
and
J
2
or J 1'
and J
2'
must be
connected.
The output
voltage
at outputs
L
and R must
be
between +4 and
-
3 dB
at
1
0 kHz,
referred
to
the 400 Hz
-20
dB
level (corresponds to
reference
point
O
dB).
.t
VU
meter
Fe, record,
Dolby: On
)
Connect
the
AF
oscillator
to the
input and
the millivoltmeter (AC)
to
the
output. Set modulation controls VR 101 and VR
1O1
' to fully
clockwise
position.
Set
the AF oscillator
to 400
Hz
and
adjust
the input
signal
at the
cas-
sette deck
in
order
to
obtain
a
reading
of
580
mV at outputs L
and
R.
Using
VR
104 and VR
.104'respectively,
set
the VU
meter
left
channel
and
the VU
meter
right
channel
to
+3 dB modulation.
Background
noise
Screen
the
amplifier
and ensure
that the
magnetic
head
is
free
of
hum.
Fe, pause,
)
Background noise at outputs
Land
R
3 mV maximum
measured
with
a
20 Hz filter (e. g. Sennheiser
FO 55, curve 22O Hz
-
3 dB)
with
rms
rectif
ication
of
meter.
HF generator
Met,
record, >
Connect the freq uency counter between test
poi nt
D
and grou nd and then
adjust
the
core of the oscillator coi
I
(L 301
)
to obtai
n a readi ng
of
105 kHz.
Connect
the millivoltmeter
(AC)
to
test point
D
and
ground. The
vol-
tage
drop
at
R 301 should be
greater than
150
mV.
HF
wave
traps
Connect
the millivoltmeter
(AC)
or oscilloscopeto R 143 {left
channel)
or
R
143'{right
channel) and,
usingcoil
L 1O3or
L
103',setto minimum
HF voltage.
HF
magnetic bias
I
nsert test cassette, Cr reference medium section,
Cr, record,
A
millivoltmeter lAC) may
be
connected
between test
point
E
(left
chan-
nel)
or
E'
(right
channel)
a
nd
grou
nd
for
basic
ad
justment.
Using V
R
1
05
or VR
'105', set
a
voltage
of 70
mV.
Depending upon
the
setting of
the tape
selector
switch, the following
voltages
will
result:
Fe
Approx.
Cr
FeCr
Approx.
Met
Tolerance
10.5
dB
42mV--4.5d8
70mV=
5dB
53mV=-2.5d8
1'l
1mV=+
4dB
Precise
alignment must be performed
as
follows:
Record
400
Hz
and 10 kHz
with
25 dB (VU meter) (with
Cr
reference
medium section). Compare the
levels
during playback.
lf the levelof both
frequencies
is
not uniform, correct
HF
bias.
Track
1
(left
channel)
is
adjusted
using
VR
105
and
frack2 (right
channel) using VR
105'.
Decrmsed HF =
treble
emphasis.
lncreased HF
=
treble
de emphasis.
lnsert test cassette, Fe reference medium section
(BASF super LH,
C 60)
Fe, record,
)
Record 400 Hz and 10 kHz
with
-
20
dB (VU
meter) .
lf
a
voltage
rise
of
the 10
kHz
level
in relation
to
the
400
Hz level
is
determined during
playback, connect
J 7. Otherwise,
i.
e. in the
case
of
a
voltage drop,
dis-
connect resistor R
3O8.
lnsert test
cassette,
metal
reference
medium section
(Scotch Metafine
c
46)
MET. record.
)
Record
400
Hz
and 10
kHz
with
25
dB (VU
meter)" Comparethe
le-
vels
during playback.
lf
a voltage rise
of
the 10
kHz
level in relation
to
the 400 Hz
level
is
determined, connect
J 8. Otherwiese,disconnect
R
31
4.
Record
level
lnsert test
cassette, Cr reference medium section
Cr, record,
Dolby: On,
)
Record 400 Hz
with 0 dB (VU
meter)
andthencheck the playback
level
at the VU
meters.
Using
VR
102 (VU
meter
left)
and
VR 102'(VU
meterright) ,adjust
the
recordlng current
so
that the playback
level
= record level.
(Approxima-
tely
4'l
0
mV should be measured at
cinch outputs
L
and R).
lnsert test cassette, Fe reference medium section
Fe, record,
Dolby: On,
)
Record 40o
Hz
with 0 dB (VU
meter) and
then
check
the playback
level
at the
VU
meters.
lf
the playback level
is higher, connect J
3
(R
132) and J 3'
\132'J.
I't
the
output
level is lower, disconnect resistor
R
134
or
R 134'.
FeCr,
I
nsert cassette
(e. g.
Sony,
ferrichrome)
FeCr, record, Dolby:
On, )
Record
400
Hz
with 0
dB (VU
meter) and
then
check
the playback
level
at the VU meters.
lf
the
payback
level
is
higher,
connect J
4
or
J 4'
.
lf theoutput
level
is
lower,disconnect R 131
or
R
131
'.
lnsert MET
cassette
(
e.
g. Scotch Metafine)
MET,
record,
Dolby: On,
)
Record
400
Hz
with 0 dB (VU
meter) and then
check
the playback
level
at the VU
meters.
lf
the
Playback level is higher.
connmt J
5
or
J
5'. lf
the output level
is
lower, disconnect R 121 or R 127'.
Overall
frequency
response
The overall frequency
response
for
all types of tape must lie within the
specif ied tolerances in accordance
with DIN 45
50O, Sheet
4. Recording
is
carried
out at
a
level
of
approximatelV
-26
dB
as
indicated on
the
VU
meters.
?