Akai X 360 D Service Manual

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Akai X 360 D Service Manual

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Page 2

TAPE SPEED DEVI ATION

1. Method involving use of pro-recorded tape.
Playback on the tape recorder to be tested tape
pre-recorded at 1,000 Hz 2 0.1% for measuring tape
speed deviation. Connect the appropriate output to a
frequency counter meter in order to measure the tape
speed deviation from the resulting deviation of the
measured frequency.
2. Method involving use of timing tape

(designed for tape speed measurement)
This method utilizes a timing tape marked at intervals of
7-1/2". The running time of the tape over 60 marked
section is measured in order to calculate the deviation of
the tape speed. In applying this method, however, it
should be born in mind that the timing tape stretch or
contract, measurement error is inevitable, so that it is
necessary to measure the total length of the tape in
advance.

WOW AND FLUTTER
Playback the 3.000 Hz pre—recorded tape whose wow

and flutter level is guaranteed to be smaller than 0.07% '

for measurement by means of a wow meter. It is also
possible for a 3,000 l-_lz sine wave to be recorded and
played for measurement by means of the wow meter. In
this case, however, the wow meter indicates a value as
much as twice the value given in the specifications on
the first page.

FREQUENCY RESPONSE
RECORD:

l),.Give a sine wave of 1,000 Hz to the Line input of
the recorder to be tested through an attenuator
from an audio frequency generator.

2) Push the “Source Button" andadjust theline input
volume so that the W meter needle indicates “D"
W.

3) Under the condition described in (2), lower the
input level 20 db by means of the attenuator.

4) Connect a microphone to the Microphone Input.
Push the tape speed selector in 7—1/2" position.

5) Start recording. Control the microphone input level
and the spot frequency in the range of 30 Hz to
25,000 Hz from the audio frequency generator and
record by talking.

' Remarks: After announcing the frequency of
each point, the the microphone
volume should immediately be rotated
back to minimum.

PLAYBACK: ".
6) Push the “Tape Monitor Button" and “Forward
Button".
7) Set the Tape Speed Selector in 7—1/2“ position.
8) Connect a Vacuum Tube Volt Meter to the line
output jack (V.T.V.M. with milli volt scale).
9) Playback the recorded tape.
10) Playback the recorded spot frequencies and make a
memo of output level and plot the value on a graph.

Audio X969 V.T.
Fre uency: A.T.‘l‘. Lure input VM.
Osc' ator Mic.i.nput ‘
, 31— Line output
Microphone jack

TOTAL HARMONIC DISTORTION FACTOR

1 K Hz
Audio Distortion
Oscillator X'BSO meter

Connect the measuring instrument as shown above; and
record the 1,000 [-12 sine wave at “0” V1). Playback the
resultant signal and measure the overall distortion factor.
Measure the noise level of the tape recorder with the
tape removed; connect the audio oscillator directly to
the distortion meter for measurement of the distortion
factor of the oscillator.

The required distortion factor may be obtained from the
results of the above measurement by the following

formula: .

do = d—dr-i'l2
where, do = Required
:1 = Overall distortion factor
J, = Noise level
:1, = Distortion factor of the oscillator

(Note: New tape of particularly good quality should be
used for measurement of the distortion factor). 7

SIGNAL TO NOISE RATIO

Set the cone Switch on “Flat" position and Playback a

tape containing a 250 Hz sine wave recorded at “O" VU

level on a standard recorder. Connect a high sensitivity
V.T.V.M. to the line outputjack and measure its output.

output.

Then remove the tape and'mcasu re the noise level under

the same conditions. Convert into decibels each of the .
measured values.