Yamaha XS250 Service Manual - Page 15

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13. Signal Indicator Test

When a sine wave of 1 kHz, -23 dBu is applied to the input, SIGNAL indicator should light up.

B BRIDGE Operation

Before performing any following adjustments, set the unit as follows:

1. Set the ATTENUATIONS at MAX.

2. Input terminal:

3. MODE switch:

4. Output terminal:

5. Connection for measuring: Measure the output at the point as shown below.

SPEAKERS

CHANNEL A

CHANNEL B

Adjustment Specifications

1. Gain Test

Check that the OUTPUT should be +22.1 +/-1.0 dBu, when asine wave of 1 kHz at -10 dBu is applied to the INPUT.

2. Frequency Response Test

When a sine wave of 20 Hz, 1 kHz or 20 kHz at -10 dBu is applied to the INPUT, check that the output is 0 +/-0.5 dB at 20 Hz and -0.5

+/-0.5 dB at 20kHz taking the 1 kHz as a reference.

3. 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

33.7 dBu

</= 0.1 %

XS250

32.2 dBu

*This test should have been finished within 30 minutes.

4. Noise Test

9-1 Set the input attenuator to "0".

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

9-3 Measure at the output, noise level should be less than -60 dBm. (LR = 8 ohm)

9-4 Set the input attenuator to "∞", noise level should be less than -60 dBu

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

C Settings after the test

The attenuator should set to "∞".

The MODE switch should set to STEREO.

D Others

0 dBu = 0.775 V

When measuring noise level,use a DIN audio filter.

Cannon connector pin 2 is HOT, pins 1 and 3 GROUND.

BRIDGE

(A ch+, B ch+) RL = 4 + 4 ohm/more than 500 W

MEASURING

INSTRUMENT

INPUT

4 Ω

GND

4 Ω

THD

20 Hz

1 kHz

20 kHz

</= 0.1 %

XS250/350