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GF-7850H(D)
SETTING
POSITION
OF SWITCH
AND KNOB
@ Volume control: Maximum
e@ Balance control: Center
e@ Graphic equalizer control: Center
e@ Power/function selector switch: (') /Tape
e Tape selector switch: Normat
e Beat cancel switch: A
BIAS
OSCILLATION
FREQUENCY
REMARKS (CHECK)
A: 85 kHz +4 kHz
(B: 88 kHz + 4 kHz)
(C: 80 kHz t 4 kHz)
BIAS
CURRENT
ERASE
CURRENT
PLAYBACK
SENSITIVITY
RECORD/
PLAYBACK
SENSITIVITY
L: VR401
R: VR402
Metal: 90 — 100 mV
(Normal: 47 — 53 mV)
(CrO2: 61 — 69 mV)
(Metal: 70 — 130 mV)
(Normal: 20 — 80 mV)
(CrO2: 40 — 100 mv)
L: VR101
R: VR102
Test tape
Normal: 580 mV
MTT-150
Non-
L: VR251
recorded
R: VR252
Playback the normal
tape recorded and
tape
adjust the semi-variable
resistor so that the
output voltage is the
same in record and
playback modes.
(MTT-502)
315 Hz,
Low frequency
oscillator
CIRCUIT ADJUSTMENT (AUDIO SECTION)
E.V: ELECTRONIC VOLTMETER
Record
miode
Record/playback
Oscilloscope
head
EV.
Frequency
counter
Figure 10—1
BIAS OSCILLATION FREQUENCY/BIAS
CURRENT
Record
Erase
mode
head
Oscilloscope
Figure 10-2 ERASE CURRENT
External
speaker
Playback
terminal
mode
Oscilloscope
E.V.
Test tape
MTT-150
Record/playback
head
3 ohms
Figure 10-3 PLAYBACK AMPLIFIER SENSITIVITY
DIN)
or @) PIN
Attenuator
Record mode
Figure 10-5 ADJUSTMENT POINT
-10-
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