Akai 1730-SS

Vil. AMPLIFIER ADJUSTMENT
<i Oscillator Circuit
Recording Head
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OSCILLOSCOPE
AUDIO
FREQUENCY
OSCILLATOR
Fig. 1
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BIAS OSCILLATOR 5
1. RECORDING BIAS FREQUENCY 2. RECORDING BIAS VOLTAGE
ADJUSTMENT (Fig. 1) ADJUSTMENT (Fig. 2)
a. Install a resistor of 10 or 50 Ohms in series with the Connect a V.T.V.M. to point (A) to (D) and adjust the
Recording Head and connect the Vertical Input recording bias voltage by turning Variable Capacitor
Terminal of the Oscilloscope to points (a) and (b). C505, 6, 7, 8 (50 to 70 PF) until it reads between AC 15
b. Feed ina sine wave signal from an Audio Frequency and 20 Volts. (The voltage of tracks 3-2 should be very
Oscillator to the Horizontal Input of the Oscil- slightly higher than that of tracks 1-4).
loscope and tune the Dial of the Audio Frequency Note: There is no way of adjusting the erasing bias
Oscillator until the Oscilloscope displays a circular voltage, but the correct bias voltage is between AC
or linear pattern. 63 and 66 Volts.
c. <A reading of 100 KHz +5 KHz (4-Ch operation),
indicates that the Recording Bias Frequency is
correct.
d. If incorrect, it can be adjusted by inserting another
condenser (C509) value 5600PF.
14