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DUI. Various Pressures
1. Pinch roller pressure
* Tie a string onto the pinch roller shaft as shown in figure 7.
|)
Capstan
Pressure
©
Roller
2. FWD
roller pressure
* Normal pressure is 600 - 1000 gr.
J25).
Fig. 7
Spring
(126)
Spring
(J26)
Lever
(J21)
Fig. 8
3. Left and right idler adjustment
* Pull the PLAY
pressure idler as shown in figure 9. Examine
the left idler pressure when the unit is set for ordinary winding
to the right; examine the right idler pressure when it is set to
Motor
Pulley
Fry wheel
Fig. 9
O
run to the left.
I. Bias Oscillator Frequency
OSCILLOSCOPE
AF oscillator
Fig. 10
As shown in figure above, connect a 10 ohm resistor in series with
the ground lead wire of the Record/Playback head.
Connect the vertical input of the oscilloscope across this resistor;
connect
the horizontal
input of the oscilloscope
to the output
terminal
of the
Audio
Frequency
Oscillator
(A.F.
Oscillator).
With this unit set to RECORD
mode and connected
as above, a
lissajous figure will appear on the oscilloscope.
Standard frequency is 80K Hz +5k Hz.
It is only necessary to measure one channel.
If the frequency is not
within the above range, change OSC
coil or C102 (0.003 mfd.).
Bias current 1.0 mA.
Proper bias is necessary
for optimum
recording.
Adjust the bias
oscillator frequency as described above. Bias current
during the
recording
is measured
at both
ends
of the connected
resistors.
Adjustment
is made by the semifixed CT-1, CT-2, so the voltage
will be 10 mV onan AC
VIVM.
Recording bias current is 1.0 mA
(voltage across the 10 ohm re-
sistor: 1.0mA x 10-8 x 10=0.01 V).
II. Gain Balance Adjustment
1. Connect an audio signal generator to the MIC jack of channel 2
and feed lk Hz 0.4 mV signal. Use an attenuator as shown below.
ATTENUATOR
600
ohm
Rocord
mode
. Operate the unit in Record position.
. Connect the VITVM across R93.
. Read the VITVM indication.
. Reconnect the VITVM across R43.
UW
& Why
n
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