Akai 4000 DB Service Manual

Page 1

~ , 35°
gist

Page 2

STEREO TAPE DECK

MODEL 4000DB

SECTION I SERVICE MANUAL ..... > ................. 3
SECTION 2 PARTS LIST ........................... 27
SECTION 3 SCHEMATIC DIAGRAM ................... 48

w

Page 5

I. SPECICATIONS

An asterisk next to a figure indicates the minimum guaranteed performance.

TRACK SYSTEM

4-track 2-channel stereo monaural system

REEL CAPACITY Up to 7" reel
TAPE SPEED 71/2 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

FREQUENCY RESPONSE

3,000 I-Iz recording and playback
30 to 23,000 Hz :3 dB at 71/2 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
RECORDING/PLAYBACK LEVEL
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

RECORDING CAPACITY
FAST FORWARD AND REWIND TIME
MOTOR

HEADS ERASE HEAD

RECORDING HEAD

PLAYEACK 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

Type: SSM-l

Revolutions: 1,500/1,800 r.p.m. at 50/60 Hz

Type: E4-200

Gap: 0.6 mm

Impedance: 2009 15% at 100 kHz

D.C. Resistance: 2n

Type: P4-154

Gap: 1 micron

Impedance: 9512 215% at 1 kHz

D.C. Resistance: 14.211

Type: Pit-150

Gap: 1 micron

Impedance: 1,250!) 215% at 1 kHz

D.C Resistance: 9052 ,

Page 9

5. TOTAL HARMONIC DISTORTION

FACTOR
Line
Audio Output Input
Frequency A.T.T. 4000DB
Oscillator
Line
Output
Input
Distortion
Meter
Fig. 6

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
small.

2. When measuring the distortion factor,
new tape should be used.

6. CROSS TALK
(Cross talk between the tracks)

5.

TAPE DIRECTION

3

-> FWD

m - REV

Fig. 7

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 No3 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.

_ Eo
c - 20 log -E _ E1 (an)

Where, C = Desired cross talk ratio (dB)
E.J = 1,000 Hz signal output level (V) -
V/II/l/A

E2 = 1,000 Hz cross talk level (V)
E1 = Non-input cross talk level (V)

7. ERASE RATIO

Line
Audio 011119111 Input
Frequency 4000DB
Oscillator
Line
Output
Input
High
Sensitivity
VrT.V.Mr
Fig. 8

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)