Yamaha EMX62M, Service Manual

Page: 32 / 63

32
EMX62M
3. Power Amplifier Check
3.1 Preparation
•
INPUT terminal: CH 5 LINE 1
•
OUTPUT terminal: SPEAKERS 1
•
Load Resistance: 4
Ω
(more than 200W)
Except otherwise indicated, the load resistance should be connected only for the power amplifier check.
•
Set the LEVEL control of CH1-4, 6 to minimum.
•
Except the above, same as the setting of 2.1.
3.2 Power ON Mute Check
Turn on the power and confirm that the mute system is released and the relay is switched on after 2.5
±
1 seconds.
3.3 Output Terminal D.C. Voltage Check
Ground input terminal and confirm that the D.C. voltage of output terminal is 0
±
100mV.
3.4 Gain Check
•
Apply -26dBs signal into the input terminal and confirm that the output level of 20.0
±
2.0dBs can be gained.
•
Confirm that the same output level can be gained at SPEAKERS 2 output.
3.5 Frequency Response Check
•
YAMAHA SPEAKERS PROCESSING Switch OFF
Apply -26dBs signal into input terminal, and confirm that the output level for 20Hz, 20kHz signal are 1, -3dB from the
level for 1kHz signal.
•
YAMAHA SPEAKERS PROCESSING Switch ON
Apply 70Hz / -26dB signal into input terminal, and confirm that the output level is within 6.5
±
2dB from the level for 1kHz input
with YAMAHA SPEAKERS PROCESSING switch OFF.
Besides, confirm that the LED lights up when YAMAHA SPEAKERS PROCESSING switch is ON and that LED goes out when
the switch is OFF.
3.6 Harmonic Distortion Rate Check
Note: This mesurement should be finished in 30 seconds.
•
Apply 1kHz signal into input terminal, and confirm that output level of 200W/4
Ω
(31.2dBs) can be gained with harmonic
distortion rate less than 0.5%.
•
Apply 20Hz, 1kHz and 20kHz signal into input terminal, and confirm that output level of 100W/4
Ω
(28.2dBs) can be gained
with harmonic distortion rate less than 0.5%.
3.7 Remaining Noise Check
Set the MASTER (MAIN) to minimum, and confirm that the noise level of output terminal is less than -68dBs.
Note: Take care not to be affected by inductive noise.
This mesurement should be performed by using DIN AUDIO FILTER.