Teac A-5500 - Bias Adjustment

SPECIFIED INPUT LEVEL SET
Wes
8.
BIAS TRAP ADJUSTMENT
ue WG
BIAS
ON PWNE
Apply
a
400
Hz
signal
at
-8
dB
to
the
LINE
IN
jacks.
Adjust
the
LINE
control
for
-8
dB
at
the
OUTPUT
jacks.
NOTE:
Do
not
disturb
the
Specified
Input
Level
position
of
these
controls
until
the
remaining
checks
and
adjustments
are
completed.
The
difference
between
the
channels
must
not
exceed
+2
dB
as
in-
dicated
on
the
Test-Set.
Adjust
VR-451/452
(L-ch/R-ch)
for
iden-
tical
level.
NOTE:
The
bias
trap
tank
circuit
keeps
the
bias
signal
from
reaching
the
record
and
monitor
amplifier
and
under
normal
"no
signal"
conditions,
voltage
should
not
be
present
at
the
OUTPUT
jacks.
.
Place
MONITOR
switch
SOURCE
position,
BIAS
switch
HIGH,
and
RECORD
MODE
switch
to
"ON".
Place
control
switches
for the
REC
"PAUSE"
mode.
Connect
a
VIVM
or
oscilloscope
across
the
RECORD
PC
Board
Test
point
and
ground.
.
Adjust
L-503/504
for
minimum
reading,
using
non-inductive
driver.
Change
the
MONITOR
switch
to
TAPE
position.
Adjust
L-651/652
for
minimum
bias
leakage
reading
at
the
OUTPUT
jacks.
spec.
-40
dB
or
less
NOTE:
This
procedure
is
simplified
using
the
PC
Board
Extender
board
(foil
side).
ADJUSTMENT
NOTE:
Adjust
bias
traps
(above)
before
proceeding.
The
follow-
ing
adjustments
are
made
only
at
9.5
cm+3-3/4
Tape
speed.
The
bias
oscillator
frequency
is
100
kHz
(+5
kHz).
.
Thread
record
Test
Tape
YIT-8003
or
equivalent
tape
on
the
unit.
.
Place
RECORD
BIAS
switch
HIGH,
EQ
switch
HIGH
position.
.
Place
MONITOR
switch
in
the
TAPE
position.
.
Apply
7
kHz
signals
at
-18
dB
to
the
LINE
IN
jacks.
.
Adjust
capacitor
VC-551/552
for
a
peak
on
the
Test-Set,
then
turn
the
capacitor
clockwise
until
a
decrease
of
2,5
dB
from
the
peak
is
obtained.