Teac A-4300SX - Bias Adjustment

RECORD PERFORMANCE
8-14 BIAS TRAP ADJUSTMENT
OUTPUTSW ...........- TAPE
RECORD MODE (L, R) SW .... ON
BIAS and EQSW .......----- 1
Select REC PAUSE mode
1. Remove all input signals.
2.
Connect
a
VTVM
or
oscilloscope
from
ground
to
the
junction
of
L-302
and
C-314
(L-ch)
and
from
ground
to
the
junction
of
L-304
and
C-329
(R-ch).
See
Fig.
8-8.
3.
Adjust
L-302
(L-ch)
and
L-304
(R-ch)
for
minimum
reading
on
scope
or
VTVM.
Use Plastic alignment tool.
Test Point
T-719
Fig. 8-8 Bias Trap Test Point
8-15 BIAS LEAKAGE CHECK
4. With Output control and Line controls at any positions
Bias Leakage should be following value at OUTPUT
jacks,
Spec. —40 dB (7.75 mV).
Check both the SOURCE and the TAPE position.
8-16 RECORD HEAD AZIMUTH ADJ.
Tape SPEEDSW...... 3-3/4 ips (9.5 cm)
NOTE: The effect of turning the azimuth screw will reg-
ister on the VTVM. A slight delay will be noticed.
Therefore, the screw must be rotated slightly with
a pause to see the effect.
~Fine Adjustment—
5. Connect a VTVM to the OUTPUT jack and an AF oscil-
lator to the LINE IN jack.
Set the oscillator to 10 kHz at —18 dB (97 mV).
6. Begin recording (Depress REC and PLAY buttons).
7. While recording, adjust the azimuth screw for maximum
reading on the VTVM.
NOTE: It is absolutely essential to accomplish the above
adjustment before performing the following adj. to
avoid phase errors greater than 45°.
8.
Sweep
the
oscillator
frequency
from
50
Hz
to
10
kHz
(for
7-1/2
ips),
50
Hz
to
7.5
kHz
(for
3-3/4
ips)
and
check
that
phase
difference
between
channel
is
45°
or
less.
9. Secure the screw with insulating locking paint.
OSCILLOSCOPE
OSCILLATOR
Ee AMPL sP
LINE INL? (L)OUTPUT
DECK
Lins] under TEST im
Fig. 8-9 Test Connection for Recording Check
8-17 BIAS ADJUSTMENT
Be
sure
the
Bias
Trap
has
been
adjusted
per
section
8-14
before
proceeding.
10.
Apply
7
kHz
signal
at
—18
dB
(97
mV)
to
the
LINE
IN
jacks.
11.
While
recording
on
the
YTT-8003
Test
Tape,
adjust
capacitor
VC-401/VC-402
for
peak
reading
on
the
VTVM,
then
turn
the
capacitor
clockwise
until
a
de-
crease
of
2.5
dB
“over-bias”
from
the
peak
is
obtained.
BIAS and EQSW .............. 2
12.
Apply
400
Hz
signal
at
—18
dB
(97
mV)
to
the
LINE
IN
jacks.
13.
While
recording
on
the
YTT-8023
Test
Tape,
adjust
VR-
401
(both
chan.)
for
an
Over-Bias
of
0.5
dB
from
the
peak.
—> OUT
— => BIAS
T- 712
Bias Limits Chart
17