Sharp GF-780H

®
CIRCUIT ADJUSTIVIENT (AUDIO SECTION)
Figure 12-1 BIAS OSCILLATION FREQUENCY
Oscilloscope
Oscilloscope
External
Speaker Jack
E.V.
Unit
Playback
Mode
Record/Playback
Mod
Record
Mode
Unit
Erase .
-~ BIij
GND.
Figure 12-2 ERASE CURRENT
Record
Mode
E.V.: ELECTRONIC VOLTMETER
e
~
E.V.
Unit
!1000hm tl~
[D
~
Frequency
Counter
I
I
-
DID
GND.
SETTING
o Dolby NR Switch: off
POSITION
.. Dubbing Spood: Normal
OF SWITCH
.. Graphic Equalizer Control: Center
AND KNOB
OIl Volume control: Maximum
o Function selector switch: Tape
e Tape selector switch: Normal
.. Beat cancel switch: 13
ADJUST·
ITEM
INPUT
MENT
REMARKS (CHECK)
POINT
BIAS
(13: 105 ± 3 kHz)
OSCILLATION -- -- (A: -9 ±0.5 kHz!
FREQUENCY
(C: -3 ±0.5 kHz)
ERASE
--
--
(Normal: 45 mV)
CURRENT
DECK 1 Test tape L: VR101 Normal: 580 mV
PLAYBACK MTT-l50 R: VR102
SENSITIVITY
DECK2
Test tape
L: VR103
Normal: 580 mV
PLAYBACK MTT-l50 R: VR104
SENSITIVITY
RECORD/
Non-
L: VR307
1. Adjust the CR os-
PLAYBACK recorded R: VR308
cillator so that the
SENSITIVITY tape electronic voltmeter
(MTT-502) reads 200 mV.
400 Hz, 2. Playback the normal
-14 dB
tape recorded and
(1 V=OdB)
adjust the semi-
variable resistor so
that the electronic
voltmeter reads
200mV.
NOTE:
1. Before checking
the bias oscillation frequency, connect
a resistor (100 ohm) between the record/playback head
and
earth.
2. Before checking the erase current, connect a resistor
(1 ohm) between the erase head and earth.
Figure
12-3 PLAYBACK AMPLIFIER SENSITIVITY
--
I-----'~..".?I Non-
Recorded
Tape
MTT-502
Unit
Unit
Line Output Playback Mode
E. V.
@
Low Frequency
Oscillator
VR30~
VR307
VRI03
'~VRI04
VRIOI
19
@ VRI02
Figure 12-5 ADJUSTMENT POINT
Figure 12-4 RECORD/PLAYBACK SENSITIVITY
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