Yamaha XM4220, Service Manual

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XM6150/XM4220
Also check that the [CLIP] indicator is lit at this time.
This test should be completed within 30 seconds of
starting.
(13) [SIGNAL] Indicator Test
Check that the [SIGNAL] indicator lights when a sine
wave of 1kHz at -23dBu is applied to the input.
2. Inspection in BRIDGE mode
<Preparation>
Input attenuation:
0 (maximum)
Input terminal:
q
[INPUT CHANNEL A]
w
[INPUT CHANNEL C]
e
[INPUT CHANNEL E]
(XM6150 only)
Cannon connector (Pin 2 HOT, pins
1 and 3 GROUND)
[BRIDGE] switches: All ON
[HPF] switch:
OFF
Output terminal:
q
[SPEAKERS CHANNEL A+B]
w
[SPEAKERS CHANNEL C+D]
e
[SPEAKERS CHANNEL E+F]
(XM6150 only)
Load resistance: 4
Ω
+4
Ω
non-induction resistance
power capacity 500W or higher
Measuring apparatus
connection: Floating ground, with load resistance
connected in between.
<Inspection>
(1) Gain Test
Check that the following output voltage is obtained
when a 1kHz, -10.0dBu sine wave is applied to the
input terminal.
XM6150: +22.1
±
1.0dBu
XM4220: +23.6
±
1.0dBu
(2) Frequency Response Test
Check that the response is within 0.0
±
0.5dB at 20Hz
and within -0.5
±
0.5dB at 20kHz using 1kHz as a reference
when sine waves at frequencies of 20Hz, 1kHz and 20kHz
at -10dBu are input to the input terminal.
(3) Total High Harmonic Distortion Test
Check that the total harmonic distortion (THD) is 0.2%
or less at the following rated outputs when a high-quality
sine wave of 1kHz is applied to the input terminal.
XM6150: 30.0dBu
XM4220: 31.7dBu
This test should be completed within 30 seconds of
starting.
3. Settings after inspection is complete
Turn the input attenuator all the way counterclockwise. Turn
off the [HPF] and [BRIDGE] switches. Set the input select
switch to EACH CH.
4. Other
0dBu=0.775V
When measuring the noise level, use an audio filter.