Sharp VC-2300G Serviceanleitung Seite 73

ADJUSTMENT OF TIMER CIRCUIT
®@ Checking of Clock Frequency
1. Connect frequency counter to pin 40 of 15001.
2. Check that one clock is emitted at the intervals of
0.99994sec to 1.00006sec.
ADJUSTMENT OF AUDIO CIRCUIT
Adjustment of Playback Level
. Play an alignment tape (with 1kHz signal recorded).
. Connect VTVM to the line output.
. Adjust R609 to attain the output level of - 5+1dB.
EE Level Adjustment
. Apply signal of 1kHz, -20dB to the audio line input
terminal.
. Connect VTVM to the audio line output terminal.
. Ground TP-601.
. Adjust R621 so that the output level is - 5+0.5db.
Bias Trap/Bias Current Adjustment
. Put the unit in RECRD mode: short-circuit the audio
input terminal.
2. Connect VTVM to both ends of the resistor of the
audio head P.W.B.
3. Adjust L605 (bias trap coil) so that VTVM reading is
maximum; then turn L605 to right (as viewed from the
rear) by 90° from that position.
4. Adjust R625 so that the bias current is 340+20uA
(3.4£0.2mV read on VTVM).
5. In AUDIO DUB mode, adjust L605 (dummy coil) so
that the VITVM indicates the same value (280 to 340A)
as that in RECORD mode.
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Figure 105.
@ Bias Leakage Checking
. Put the unit in RECORD mode: short-circuit the audio
input terminal.
. Connect VTVM to the line output terminal.
. Bias leakage must be less than - 20dB.
Checking of Erase Oscillation Frequency and Erase Voltage
. Put the unit in RECORD mode: no input signal is
needed.
. Connect a frequency counter to TP-604.
. Adjust L604 so that the counter reads 73+5kHz.
. Connect an osciloscope to TP-604.
. The oscillation voltage must be more than 90Vp-p.
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@ Playback Equalizer Adjustment
Connect VTVM to the line output terminal.
1. Using an audio signal generator, apply sine wave signal of
~35dB to the audio input terminal.
2. Record 400Hz and 5kHz signals for a few seconds,
respectively.
3. Reproduce such recorded signals. Adjust R608 so that
the output of 5kHz signal is -0.5dB (on VTVM) in level
as compared with that of 400Hz signal.
4. Once again check the play output by using an alignment
tape.
®@ Record Level Checking
Connect VTVM to the line output terminal.
1. Using an audio signal generator, apply signal of 1kHz,
~20dB to the unit, and record and play it back.
2. Then check that the play output level is - 5+3dB.
3. Apply the same signal as in Adjustment of playback level
to the unit which is set in AUDIO DUB mode, and record
and play it back.