Akai X 2000 SD Service Manual

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Akai X 2000 SD Service Manual

Extracted text from Akai X 2000 SD Service Manual (Ocr-read)


Page 5

ll. MEASURING METHOD

TAPE SPEED DEVIATION

1. Method involving use of pre—reeorded tape.

For measuring the tape speed deviation, play back the

pre—recorded tape at 1,000 Hz i 0.1%. 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 over 60 marked sections of

tape is measured in order to calculate the deviation of

the tape speed. In applying this method, however, it

should be kept 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 of which the
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 3,000Hz 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 specifi-
cations on the first page.

SIGNAL T0 NOISE RATIO

X-20005D

Line output V.T.V.M.

Set the Equalizer Switch on “7-1/2” ips position and
playback a tape containing a 250 Hz sine Wave recorded
at “O" VU level on a standard recorder.

Connect a V.T.V.M. to the line output jack of the
recorder and measure its output.

Then remove the tape and measure the noise level under
the same condition. Convert each of the measured values
into decibels.

TOTAL HARMONIC DISTORTION FACTOR

1 Kc/s
Audio Distortion
Oscillator X‘QOOOSD Meter

Connect the measuring instrument as shown above, and
record the 1,000 Hz sine wave at “0” VU. 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—di -d2
where, do = Required
d = Overall distortion factor
d1 = Noise level
d2 = Distortion factor of the oscillator

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

POWER OUTPUT

Playback a tape containing a 1,000 Hz sine wave
recorded at 0 VU on a standard recorder.

Connect a V.T.V.M. to the line output jack of the
recorder and measure the voltage at the output of the
recorder to be tested.