BIAS CURRENT AND BIAS OSCILLATION FREQUEN-
CY ADJUSTMENT OF RECORD AMPLIFIER
(See Figure 5-l) SW7 is not used for model
Connect VTVM between the test point
(or
and ground.
2. Connect the vertical input terminal of oscilloscope to
the VTVM and its horizontal input terminal to CR
oscillator.
3. Apply the signal
from the CR oscillator to the
unit, and push the tape selector switch SW4.
4. Place the unit in record mode and adjust bias oscillation
coil
so that the bias oscillation frequency is
while watching Lissajous’ figure on the oscillo-
scope.
5. Push tape selector switch
6. Adjust semi-variable resistor VR301
so that
VTVM indicates 70
7. Make sure the indicated value of VTVM varies according
to each position of tape selector switch as tabulated
below.
n
ERASE VOLTAGE CHECK
(See Figure 5-2)
Connect VTVM between test point
and
2. Connect oscilloscope to the output terminal of VTVM,
3. Push the tape selector switch SW6.
4. Place the unit in record mode, then see that VTVM is
value 210
n
RECORD/PLAYBACK HEAD AZIMUTH ADJUSTMENT
(See Figure 5-3)
Connect VTVM between the test point TP103 (or
TP203) and ground.
2. Push the tape selector switch SW4 and set the Dolby
switch SW3 at off position.
3. Put a test tape
MTT-114,
250
-10
recorded) into the unit and play it.
4. Adjust the head azimuth adjusting screw so that the
indicated value of VTVM reaches the maximum and a
difference in phase becomes as small as possible.
PLAYBACK FREQUENCY CHARACTERISTIC CHECK
(See Figure 5-4)
1. Connect VTVM to the line output socket.
2. Push the tape selector switch SW4 and set the Dolby
switch SW3 at off position.
3. Put a test tape (TEAC,
12.5
40 Hz, 250
-10
recorded) into the unit
and play it.
4. See that VTVM is showing the deviation of two different
input signals (40
and 12.5
against the 1
input, as tabulated below.
Posit ion
Switch
Indicated value
I
normal
Push SW4
37
Fe
Push SW7
Push SW5
41
52
Figure
Figure 5-2
Figure 5-3
Test Tape
W ith 40 Hz input
Deviation against 1
input
shown by VTVM
W ith 12.5
input
-3
to 4
I
Figure 5-4
