Akai GXC-570D

2. DOLBY NOISE REDUCTION CIRCUIT
ADJUSTMENT (Refer to Fig. 22)
NOTES: 1. Because the establishment of the
(5 kHz) adjustment signal and level etc.
is vital to correct Dolby Noise Reduc-
tion circuit adjustment, use only cal-
ibrated measuring instruments.
2. Level deviation must be within +0.5 dB.
3. After Dolby Noise Reduction circuit
adjustments have been made, do not
change recording and playback levels.
. RECORDING DOLBY NOISE REDUCTION
AMPLIFIER ADJUSTMENT
(Refer to Fig. 22)
1) Set Monitor Switch to “SOURCE”, and Tape
Selector Switch to “LOW NOISE”.
2) Ground Test Point TP2 and turn adjustment semi-
‘fixed resistors VR4 (50 kB) and VRS (5 kB) as far
as thiey will go in the direction of the arrow mark.
3) With Line Recording Level Volume set to 12
o’clock position, supply a 5 kHz signal to the line
input and obtain a —28.5 dBm line output level.
4) Connect a Voltmeter to the center terminal of
EQ P.C Board Rec Level Volume VRI1 (left
- channel) and VR1b (right channel), and adjust Rec
Level Volume obtain a —30 dBm AC Voltmeter
indication.
5) With the Dolby Noise Reduction Switch at ON,
adjust semi-fixed resistor VR4 (50 kB) shown in
Fig.18 to obtain a —20dBm level at center
terminal of Rec Level Volume.
6) Disconnect Test Point TP2 from ground and adjust
semi-fixed resistor VR5 (5 kB) shown in Fig. 22 to
obtain a —22 dBm level at center terminal of Rec
Level Volume.
. PLAYBACK DOLBY NOISE REDUCTION
AMPLIFIER ADJUSTMENT ,
(Refer to Fig. 22)
1) Set Monitor Switch to “TAPE” and Tape Selector
Switch to LOW NOISE.
2) Ground Test Point TP1 and turn adjustment semi-
fixed resistors VR2 (50 kB), and VR3 (5 kB) as
far as they will go in the direction of the arrow
mark.
3) Set deck to playback mode.
4) Supply a. 5 kHz signal to terminal (13) shown in
Fig. 18 and obtain a -20 dBm line output level.
5) Set the Dolby Noise Reduction Switch to ON and
adjust semi-fixed resistor VR3 (5 kB) to obtain
a —30.5 dBm line output level.
6) Disconnect Test Point TP1 from ground and adjust
semi-fixed resistor VR3 (5 kB) to obtain a —28.5
dBm line output level.
Noise reduction circuit made under license from
Dolby Laboratories Inc. The word ‘DOLBY’ and the
Double-D symbol are trademarks of Dolby Labor-
atories Inc.
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