Akai M 7 Service Manual

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AKAI TAPE RECORDER

MODEL M'7

SERVICE MANUAL

TABLE OF CONTENTS
I SPECIFICATIONS ............................ I
1] HOW TO MEASURE DESIGNATED VALUES

IN SPECIFICATIONS ............................ 2
111 LOCATION OF CONTROLS ...................... 3
Iv DISASSEMBLV TO REMOVE TAPE TRANSPORT

UNIT AND AMPLIFIERS ...................... .. 4
v TRANSPORT MECHANISM ........................ a
V1 ADJUSTMENT OF TAPE TRANSPORT UNIT .......... 9
VII ADJUSTMENT OF AMPLIFIER .................... 10
VII] MAINTENANCE PROCEDURES .................... II
Ix SCHEMATIC DIAGRAM .......................... 12
V TROUBLE SHOOTING CHART .................... 14

XI CONNECTING DIAGRAM ........................ 18

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MODEL NUMBER:

WEIGHT (NET

IN CARTON) :

DIMENSIONS

POWER

REQUIREMENTS :

POWER

CONSUMPTION :

RECORDING

SYSTEM :

PLAYBACK

SYSTEM :

TAPE SPEED

TAPE SPEED

DEVIATION :

WOW AND
FLUI'IER

FAST FORWARD
AND REWIND

TIME :

FREQUENCY

RESPONSE :

DISTORTION

SIGNAL-TO-

NOISE RATIO :

CROSS TALK
CHANNEL

SEPARATION :

POWER INPUT

LEVELS :

I SPECIFICATIONS

Akai Model MJI, portable 4-track
stereo tape recorder.

47.3 lbs. (21.5 kg.) for M7

2.4 lbs. (1.1 Itq.) for all accessories
supplied.

20'HX13'WX9D, overall, case clov
sed. (510H>.<34OWX226D in rn/m)

AC. 100, 110, 117, 200, 220, 230
or 245 volts interchangeable. 50-60

cycles.
100 VA.

Specific "cross-field" recording based
on the theory of trailless recording
bias system. Inline 4 track stereo
and 4-trackmonaural recording.

Inline 4-track stereo. monaural and
2-track stereo playback. Playback
of monaural double-track and full-
traclc recordings also possible.

Three speeds; 7}? (190m), 3-%
(9.5 cm.) and 1-% (4.75 cm.) per
second.

Less than £3 per cent at all tape
speeds.

Less than 0.15% R.M.S, at 7&5 ips.
Less than 0.25% R.M.S. at 3% ips.
Less than 0.35% R.M.S. at 1-K ipa.

90 seconds for 1,200 It. tape at 50
cycles and 75 seconds at 60 cycles.

40 to 23,000 cps. at 7-1/, ips i3 db;
40 to 20,000 cps. at 3% ips *3 db;

40 to 10,000 cps. at 1-% ips #4 db.
Within 3 per cent T.H.D. at all
speeds.

40db below recorded level signal
at all speeds.

: Within 53 db between each track.

Better than 60 db at 1,000 CPS 3 VU.

Microphone Input level

POWER
OUTPUT

INSULATION
RESISTANCE :
INSULATION
YIELD
STRENGTH :

MONITORING
SYSTE M
MOTOR

HEADS

MICROPHONE
USED

SELF-CONTA I NED
SPEAKER :

TUBES USED

REEIS USED

RECORDING
LEVEL
INDICATOR :

-55 db (VR. max) at 1,000 cps.
Phono and radio input level
-15 db (VR. max) at 1,000 cps.

Head output, 1 mv. at 1,000 cps.
Pro-Amplifier output, 0.8 V at 1,000
cps, impedance 10,000 ohms

Main output, 34 dbm. up

(in 600 ohms).

More than 10 MEG ohms

More than one minute at A.C.
1,000 V with Headphone

[8 ohms) during recording.
Hysteresis synchronous,
motor, Capacitor start.
1/100 HP. Power ratio, 70 per cent.
3,000 to 1,500 rpm at 50 cps,

3,600 to 1,800 rpm at 60 cps.

Inline Iourztrack stereo/monaural re-
cord-play head;

Impedance-5,000 ohms at 1.000 cps.
Four-track. cross-field bias head ,-
Impedance---14,000 ohms at 60 kc.
Four-track erase head:
Impedance-"18,000 ohms at 60 kc.

Square-shaped, dynamic microphonc
Impedance-"50,000 ohms
Sensitivity-"55 db.

Frequency Response-~70 to 15,000
cps :i: 10 db.

5X7' (12X 16 cm), oval-shaped,

dynamic speaker:
Impedancen-B ohms
Allowable Input-"6 watts
Frequency ResponseH-BO to
12,000 cps, i 10 db.

6267 (EFBS) X 2, (12AD7) X 2,

6805 x 2. 6X4 X 2, 6AR5 X 1.

: Up to 7' reel

Horizontal, A-mcdel VU meter

two-speed.