Yamaha XS350 Servis Kılavuzu - Sayfa 14

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XS250/350

7. Harmonic Distortion Test

When a high quality sine wave is applied at 20 Hz, 1 kHz or 20 kHz, the harmonic distortion should be as follows:

Power output level (4 ohm)

XS350

350 W + 350 W (33.7 dBu/ch)

XS250

250 W + 250 W (32.2 dBu/ch)

*This test should have been finished within 30 minutes.

8. Channel Separation Test

8-1 Apply a -5 dBu, 20kHz sine wave into the channel A.

8-2 Short the input for the channel B with a 600 ohm load.

8-3 Set the output of the channel A at a reference of 0 dB.

8-4 If channel B attenuator is set to the same as channel A, channel B output should be l

ess than -65 dB. (RL = 8 ohm)

9. Noise Test

9-1 Set the input attenuator to MAX.

9-2 Short the input with a 600 ohm load.

9-3 Measure at the output, noise level should be less than -65 dBm.

9-4 Set the input attenuator to "∞", noise level should be less than -70 dBu.

*Be careful that it is not affected by noise induced during this inspection.

10. Stability Test

When a rectangular wave 10 kHz, -10 dBu is applied to the input and a capacitor 10 pF–0.47 µF is connected with 4 ohm load resistor in

parallel, the overshoot and the ringing should be as follows.

Oversshoot:

Vp/Vo </= 1.8

Ringing: less than 5 waves

Next, when the 4 ohm load resistor is removed and the load is the capacitor 10pF–0.47 µF only, the overshoot and the ringing should be

as follows.

Oversshoot: Vp/Vo </= 2.5

Ringing:

fade away in less than 7 waves and no oscilation

11. Protection Circuitry Test

Check that the relay does not work when you apply a sine wave of +5.0 dBu (XS350), +3.0 dBu (XS250) at 10 Hz to the input and adjust

the input level to obtain a clipped output wave form.

Next, check that when you apply a sine wave of 1 Hz, 0.0 dBu to the input, the signal is cut off within 2 seconds, and the PROTECTION

indicator should light up.

Finally, check that when no signal is applied, the amplifier would resume to normal operation within 10 seconds.

12. PC Limiter Circuitry Test

Check that the OUTPUT should be as follows with an oscilloscope when a sine wave of 0 dBu (XS350), -1.5 dBu (XS250) at 1 kHz is

applied to the INPUT and the output is shorted with a 1 ohm load ( +/-5%). At this time, check the CLIP indicator lights.

Model

Output level

XS350

Vp-p </= 25V

XS250

Vp-p </= 20V

*This test should have been finished within 30 minutes.

THD

20 kHz

1 kHz

20 kHz

</= 0.1 %