Teac A-3340 - OVERALL SIGNAL-TO-NOISE RATIO; ERASE EFFICIENCY MEASUREMENT

OVERALL
SIGNAL
TO
NOISE
RATLO——————OOOOOOOOOOOOOOO
i)
ERASE EFFICIENCY
nN.
5.
6.
nu
IMPORTANT
Clean
and
demagnetize
the
heads
before
proceeding.
It
is
ex-
tremely
important
that
all
tests
described
in
the
proceeding
paragraphs
have
been
completed
and
that
all
controls
adjusted
are left unalterd.
Thread
a
record
test
tape
(Scotch
203)
on
the
unit.
Remove
the
AF
oscillator
from
the
LINE
IN
jacks.
Place
the
unit
in
the
RECORD
mode
with
no
signal
applied.
BIAS
switch
in
HIGH
position.
NOTE
Noise
readings,
when
taken
while
recording,
may
be
affected
by
the
bias
signal
which
could
be
leakings
through.
It
is
therefore
good
practice
to
rewind
the
no
signal
recorded
section
and
take
the
noise
reading
during
playback.
Note
the
point
on
the
index
counter
where
recording
begins.
-
Rewind
the
tape
and
play
it
back.
The
noise
level
as
indicated
on
the
level
meter
should
be
-56
dB
or
less.
(See
figure
7-5
Computation
Section.)
NOTE
Bias,
erase
and
playback
amplifier
noise
are
all
included
in
this
measurement.
All
frequencies
between
40
Hz
and
15
kHz
are
measured
un-
weighted.
NOTE
To
measure
erase
efficiency,
a
1
kHz
band
pass
filter
(TEAC M 204 CL filter) must be used.
Due
to
the
high
level
of
this
signal,
it
is
recommended
that
only
a
short
recording
be
made
(approximately
30
seconds)
to
prevent
damage
to
the
VU
meter.
.
Apply
a
1
kHz
signal
at
0
dB
to
the
LINE
IN
jacks.
Place
the
unit
in
record
mode
and
record
this.
signal.
Rewind
the
recording
to
the
beginning
and
remove
the
AF
oscil-
lator
from
the
LINE
IN
jacks.
:
Place
the
unit
in
RECORD
mode
and
record
over
this
portion
of
tape
again.
;
Rewind
the
tape
to
the
starting
point
and
connect
a
level
meter
to
the
OUTPUT
jack,
through
the
1
kHz
band
pass
filter.
Play
the
erased
portion
of
the
tape.
7.
The
level
meter
should
indicate
-60
dB
or
less.