Yamaha EMX 660, Service Manual

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EMX660
22
3-9 Protection
Apply a 10 Hz sine wave signal to the input; increase the input signal so that the output signal is clipped. Confirm
that the protection function operates and that the speaker relay does not open.
When a 1 Hz, 6 Vp-p (8.7 dBs) sine wave signal is applied to the input, confirm that the protection function operates
within 2 seconds and the speaker relay is turned off. When the input signal is turned off, confirm that the protection
function stops and the speaker relay automatically turns on within 5 seconds.
3-10 PC Limiter and Limiter
Apply a 1 kHz -20 dBs sine wave signal to the input and then connect a 1 ohm ( +/- 5% 100 W) resistor; confirm that the
output signal is Vp-p 25V and that the signal is not rectangular.
3-11 LIMITER Indicator
When a 1 kHz -10.8 dBs sine wave signal is applied to the input, the LIMITER indicator should light up.
3-12 Efficiency
When the output of POEWR AMP1 and 2 is adjuster to 12.2V (24.0 dBs), confirm that the primary power is 180
+/- 50W.
4. Main Bridge
4-1 Setting Conditions
Input Terminal: INPUT CH 5 LINE 1
POWER AMP switch: MAIN BRIDGE
Measuring Output Terminal: BRIDGE
Output Load: 8 ohm (more than 600 W)
INPUT CH 1- 4, CH 6
LEVEL level control: Minimum
Note: Other control settings are the same as those for the mixer in section 2-3.
4-2 Connection
Tip Measuring instruments input
4 ohms
Phone Plug Measuring instruments ground
4 ohms
Sleeve
4-3 Gain
Apply a 1 kHz -26.0 dBs sine wave signal to the input; confirm that the output levels is are +22.0
±
2 dBs.
4-4 Frequency Response
Apply a -26dBs signal to the input terminal and check that the output voltage when the signal frequency is
20Hz and 20kHz is 1 and -6dB ranges respectively, using the output voltage at 1kHz as reference.
5. Power Supply Fluctuation
There should be no operational problems when the power voltage is varied /- 10% of the nominal
voltage.
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