Akai GX-747 dbx Service Manual

STEP
1
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5
6
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7
8
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9
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10
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11
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12
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14
ADJUSTMENT
•
ITEM
FWD Playback
Level
REV
Playback
Level
REC Peaking
BIAS OSC
BIAS
Current
FWD
Recording
Level
REV
Recording
Level
Bias leak
NORMAL
Position FWD
Frequency
Response
NORMAL
Position REV
TEST TAPE
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SUPPLY SIGNAL
!MODE
700 Hz 7-1/2 ips.
FWD!
0 VU Test Tape
700 Hz 7-1/2 ips.
REV!
0 VU Test Tape
23.2 kHz from
an Oscillator
REC
REC
REC
NORMAL Blank
Tape 1
000 Hz · FWD/
i-5 .5 dBm' Recording i REC
I
NORMAL Blank
Tape 1,000 Hz
REV/
i -5 .5 dBm Recording
REC
No signal input
Mic and Line
REC
Volume are MAX.
NORMAL Blank
i
Tape 1.5 kHz,
FWD/.
15 kHz -25.5 dBm
REC
Recording
NOR.\1AL Blank
Tape 1.5 kHz,
REV/
Frequency
• 15 kHz -25.5 dBm REC
Response
Recording
EE Position
EE Blank Tape
Frequency 1.5 kHz,
20 kHz
FWD,
Response
-25.5 dBm
REV/
(3-3/4 ips)
Recording
REC
EE Position
EE Blank Tape
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Frequency
1.5 kHz, 25 kHz
FWD,.
Response
-25.5 dBm
REV/
(7-1/2 ips)
Recording
REC
FWD
i
Distortion
1,000 Hz
-5 .5 dBm • FWD/
Recording
I REC
Confirmation
REC
!
Distortion
1,000 Hz
-5.5 dBm REV/
Recording
I REC
Confirmation
ADJUSTMENT
POINT
YRS 50 kB
VR6
SO kB
VLl lmH
Tl
VR3 20kB
VR2 20kB
VRl 20kB
FLl
(Mic Amp PCB)
VCl
VC2
VR410kB
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VR9 30 kB
RESULT REMARKS
• -5.5±0.5 dBm•
i (410 mV) !
I -5.5±0.5 dBm I
(410 mV)
! Maximum AC
Voltmeter
indication
Set TAPE SELECTOR
to "NORMAL"
Tape Speed 3-3/4 ips.
See NOTE 6,
7, 9 and
Figs. 9-3,
94, 9-5.
Set TAPE SELECTOR
to "NORMAL"
100 ± 0.5 kHz ·
Tape Speed 7-1/2 ips.
Connect a Frequency
Counter
between TP
and GND. Fig.
9-5.
140±2 mV
-5 5+0 5 dBm
. - .
(410mV)
! -5.5±0.5 dBm
I
(410 mV)
i
Minimum
1.5 kHz,
15 kHz
flat
1.5 kHz,
15 kHz
flat
1.5 kHz,
20kHz
flat
1.5 kHz,
25 kHz
flat
NORMAL:
EE
See NOTE 8.
NORMAL:
EE
:
See NOTE 8.
Set TAPE SELECTOR
to "NORMAL"
Tape Speed 7-1/2 ips.
Connect a
AC Volt-
meter between TP and
GND Fig. 9-5.
Tape Speed
3-3 /4 ips.
Recheck Recording
Level. See
NO'TE 10.
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Tape Speed 3-3/4 ips.
Recheck Recording
Level. See
NO'TE 10.
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Tape Speed J.3/4 ips.
Recheck Recording
Level. See NO
TE 10.
Tape Speed
7-1 /2 ips.
Recheck
Recording
Level. See NO'"TE 10.
Less
than 0.5%
Less
than 0.4%
Less
than 0 .5 %
Less
than 0.4%
---------------SERVICE MANUAL GX-747dbx---------------
37
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Akai GX-747 dbx Specifications

General

Track System	4-track, 2-channel stereo
Reel Size	up to 10.5 inch reel
Type	Reel to Reel
Heads	2 x erase
Motor	1 x capstan, 2 x reel
Tape Speed	9.5 cm/s, 19 cm/s
Wow and Flutter	0.03% (19 cm/s)
Signal to Noise Ratio	65dB
Input	1 x line, 1 x microphone
Output	1 x line
Dimensions	440 x 480 x 260 mm