This is the 54 pages manual for Akai 4000 DB Service Manual.
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STEREO TAPE DECK
SECTION I SERVICE MANUAL ..... > ................. 3
SECTION 2 PARTS LIST ........................... 27
SECTION 3 SCHEMATIC DIAGRAM ................... 48
An asterisk next to a ﬁgure indicates the minimum guaranteed performance.
4-track 2-channel stereo monaural system
REEL CAPACITY Up to 7" reel
TAPE SPEED 7‘1/2 and 3-3/4 ips,:2% 023%)
Playback a 1,000 Hz 7-1/2 ips. pie-recorded test tape
WOW AND FLUTTER Less than 0.15% (*0.22%) at 7-1/2 ips.
Less than 0.2% (*0.3%) at 3-3/4 ips.
Playback a 3,000 Hz pre-recorded test tape
TOTAL WOW AND FLUTTER *Less than 0.28% at 7-1/2 ips
3,000 I-Iz recording and playback
30 to 23,000 Hz :3 dB at 7‘1/2 ips.
30 to 16,000 Hz :3 dB at 3-3/4 ips.
WIDE RANGE ‘40 to 22,000 Hz :3 dB at 7—1/2 ips.
(AKAI SRT TAPE) *40 to 14,000 Hz :3 dB at 3-3/4 ips.
LOW NOISE *40 to 20,000 Hz 13d B at 7-1/2 ipx
(SCOTCH #211 TAPE) *40 to 14,000 Hz :3 dB at 3-3/4 ipsl
DISTORTION FACTOR Less than 1.0% (1,000 HZ 0VU recording)
TOTAL DISTORTION FACTOR ‘Less than 1.5% at 7-1/2 and 3-3/4 ips.
PLAYBACK OUTPUT LEVEL LINE OUTPUT
1,000 I-Iz 0VU recording SCOTCH #211 tape
0.775V (0 dBm t 1.0 dB) using a 250 112 7-1/2 ips. pre-recorded test tape
DIN OUTPUT 0.5V
HEADPHONE OUTPUT 30 mV at Sn 1
INPUTS MIC INPUT More than 0.4 mV 1
LINE INPUT More than 70 mV
DIN INPUT More than 2.5 mV/low and 75 mV/high
WIDE RANGE 0 :0.5 dB 1,000 Hz 0VU recording
LOW NOISE 0 :1.0 dB 1,000 Hz 0VU recording
SIGNAL TO NOISE RATIO
TOTAL SIGNAL TO NOISE RATIO
Better than 55 dB (*50 dB)
*Better than 45 dB
Recording volume at 180 degree position from MIN.
CROSS TALK Better than 65 dB (*60 dB) (monaural)
Better than 40 dB (stereo)
1,000 Hz +3 VU recording
ERASE RATIO Better than 70 dB 1,000 Hz +3 VU recording
RECORDING BIAS FREQUENCY 105 kHz 15%
BIAS LEAK Less than v25 VU Dolby SW OFF, Monitor SW TAPE
HIGH FREQUENCY DEVIATION
FAST FORWARD AND REWIND TIME
HEADS ERASE HEAD
Within 2 dB
Playback a 8,000 Hz 3-3/4 ipc pres-recorded test tape at 7-1/2 ips
90 min. stereo recording using a 1,800 ft. tape at 7-1/2 ips.
Within 4 mini and 40 sect/3 min. 40 sec. using a 1,800 ft. tape at 50/60 Hz
4-Pole Induction I-Speed motor
Revolutions: 1,500/1,800 r.p.m. at 50/60 Hz
Gap: 0.6 mm
Impedance: 2009 15% at 100 kHz
D.C. Resistance: 2n
Gap: 1 micron
Impedance: 9512 215% at 1 kHz
D.C. Resistance: 14.211
Gap: 1 micron
Impedance: 1,250!) 215% at 1 kHz
D.C‘ Resistance: 9052 ,
5. TOTAL HARMONIC DISTORTION
Audio Output Input
Frequency A.T.T. 4000DB
Connect the measuring instruments as shown in
Fig. 6 and record a 1,000 Hz sine wave signal at
0 VU. Playback the resultant signal and measure
the overall distortion factor.
NOTE: 1. At this time, distortion of the Audio
Frequency Oscillator must be sufficiently
2. When measuring the distortion factor,
new tape should be used.
6. CROSS TALK
(Cross talk between the tracks)
m ‘— REV
As shown in Fig. 7 first record a 1,000 Hz sine
wave signal on track No. 3 at +3VU level. Next,
record under a non-input condition Then playback
the tape on track No‘3 and 1' (reversed condition
of tape) through the B.P.F. (1,000 Hz Band Pass
Filter, sensitivity 1,000 Hz, ratio 1:1) and obtain
the ratio from the following formula.
c - 20 log —E‘ _ E1 (an)
Where, C = Desired cross talk ratio (dB)
E.J = 1,000 Hz signal output level (V) -
E2 = 1,000 Hz cross talk level (V)
E1 = Non-input cross talk level (V)
7. ERASE RATIO
Audio 011119111 Input
As shown in Fig. 8, connect a High Sensitivity
V.T.V.M. to the Line Output. Playback a virgin
tape and take a V.T.V.M. reading of the output level.
Next record a 1,000 Hz sine wave signal at +3VU,
then playback this recorded signal and take a
V.T.V.M. reading of the output level. Next, using
this pre-recorded tape, record under a non-input
condition and take a reading of the noise level
output of the erased signal and obtain a ratio bet-
ween the two from the following formula:
Er = 20 log % (as)
2 - I
Where, Er = Desired erase ratio (dB)
Eo= 1,000 Hz signal output level (V)
E2 = Non-input signal recorded level (V)
E = Virgin tape noise output level (V)