Yamaha EMX3000 Service Manual page 32

EMX3000
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10 PROTECTION CIRCUIT
• With a signal input to POWER AMP IN (L), clip the output waveform of the 10Hz signal and check that the protection circuit
functions to prevent the relay from opening.
• Check that the protection circuit functions within 2 seconds to shut off the output when a 1Hz, Vp-p=10V(13.2dBs) signal is
input and the output is restored automatically within 5 seconds when the input signal is stopped.
11 PC LIMITER CIRCUIT, LIMITER CIRCUIT, LIMITER INDICATOR
• With 1 ohm load resistance (+/- 5%, 100W) connected to the output terminal, input a 0dBs signal to the input terminal and
observe the output terminal using an oscilloscope. Then the protection circuit should function to shut off the output and the
output is restored automatically within 5 seconds when the input signal is stopped.
12 EFFICIENCY
• Input a -5.6dBs signal and check that the primary voltage is 190 +/- 50W. 12.2V (24.0dBs) output should be obtained at
SPEAKER OUT 1 and 2 at this time.
INSPECTION OF MAIN BRIDGE
1 PREPARATIONS
• Input terminal: ST BUS IN 1 L/MONO
• POWER AMP Switch : MONO BRIDGE
• POWER AMP (L/BRIDGE, R) level control : Maximum
• Output terminal: BRIDGE
• Load resistance: 8 ohm (600W or more)
Unless otherwise specified, the load resistance of the speaker should be connected only when performing inspection.
• Set all the Fader/Level controls of channels 1 to 10, SUB IN 2 and TAPE IN to the minimum position.
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L 13942296513
• Other than the above, use the same settings as described under "Inspection 1" for inspection.
• Connection of measuring equipment
2 GAIN
• Input a -12.0dBs signal to the input terminal and check that +20.0 +/- 2 dBs output is obtained.
3 FREQUENCY RESPONSE
• Input 20Hz, 1kHz, 20kHz/-12.0dBs signals to the input terminal and check that the frequency response at 20Hz and 20kHz is
within the range of +1.0/-3.0dB with 1kHz used as a reference.
C. OTHER INSPECTIONS
1 POWER VOLTAGE VARIATION
• Check that no abnormality occurs with operation even when the power voltage is varied by +/- 10%.
D. FACTORY SETTINGS
• EQ GAIN, GEQ GAIN
• All VR and fader controls other than above
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• All push switches
• PHANTOM switch
• POWER AMP switch
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• POWER AMP LEVEL VR
• POWER switch
• PROGRAM switch
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4Ω
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4Ω
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CENTER
Minimum
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OFF
ST1L-ST1R
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Maximum
OFF
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Measuring equipment input
Measuring equipment GND
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