Inspection Of Power Amplifier; Ein; Residual Noise; Phantom - Yamaha EMX5000-12 Service Manual

12 EIN

• In the state as described in 1, set only the fader and GAIN control VR of the channel being measured to the MAX position, turn
PAN or BAL VR counterclockwise fully, set the fader of all the other channels to the MIN position and short-circuit the INPUT
A terminal with 150 ohm. Then check that the noise level obtained at ST OUT L is -43dBs or less.
• If it exceeds -43dBs, calculate the input converted noise level of each channel and check that the result is -127dBs or less.
(Use the DIN audio filter.)

13 RESIDUAL NOISE

• In the state as described in 1, set all Fader/Level controls in the INPUT section to the MIN position. Then set the Fader/Level
controls in the MASTER section to the MAX or MIN position and check that the noise level at ST OUT, MONO OUT, AUX
SEND and EFFECT OUT (without MASTER level control) is at the level indicated in Table 10-1 or less.
[Table 13-1]
fader/level control ST OUT (L, R)
MAX -73
MIN -95

14 PHANTOM

• Connect a 10k ohms load resistance between pins 1 and 2 of INPUT A to short-circuit between pins 2 and 3. Then check that
+35±3 V voltage is obtained at both ends of the load resistance when the PHANTOM switch is turned on.
15 LAMP TERMINAL
• The voltage at the LAMP terminal should be 12±1V (DC) (30 ohm load)
Measure the voltage between pins 2 and 3.
16 DIGITAL EFFECT
• In the state as described in 1, input -36 dBs signal to CH1 INPUT A and set AUX1 level control to the MIN position and
EFFECT1 level control as well as the CH fader to the MAX position.
Then with the PROGRAM select switch set to 16, PARAMETER VR to MIN and AUX1 EFFECT RTN VR to the MAX position,
check that the output signal level at AUX1 OUT is larger than 0dBs when the DIGITAL EFFECT ON switch is turned on.
17 STAND-BY
• In the state as described in 1, apply a signal from CH INPUT A and set the level of ST OUT (L o R) / AUX SEND (1 o 2) /
EFFECT SEND (1 o 2) output terminals to +14dB. Then turn on the STAND-BY switch and check that the output level is –
46dB or less and that the LED flashes.
18 STABILITY
• Connect a load resistance to the power amplifier output for this inspection.
• Check that no abnormality such as oscillation occurs when a 10pF to 0.1µF capacitor is connected in parallel with a load
resistance at each output terminal.
• Check that no abnormality such as oscillation occurs when all faders, level controls and equalizer are set to the MAX position.
(Short-circuit the input terminal with 150 ohm.)
B. INSPECTION OF POWER AMPLIFIER
Inspection of SIGNAL SELECT switch MAIN L – MAIN R, AUX1 – AUX2
1 PREPARATIONS
• Input terminal: ST SUB IN 1 L/MONO
• SIGNAL SELECT switch: MAIN L-MAIN R
• POWER SELECT switch: 500W+500W
• Output terminal: SPEAKERS A2, SPEAKERS B2
• Load resistance: 40 Ω (500W or more)
Unless otherwise specified, the load resistance of the speakers should be connected only when checking the power amplifier.
• Set INPUT CH1-20 (EMX5000-20) / CH1 – 12 (EMX5000-12), ST SUB IN 2 and 2TR IN level controls to the MIN position.
• Other than the above, use the same setting as described under PREPARATIONS for inspection.
2 Muting function at power ON
• Check that the muting function is cancelled and the relay turns on at 2.5±1 seconds after the POWER switch is turned on.
MONO OUT AUX 1,2 SEND
-73 -70
-93 -95
EFFECT SEND PHONES
-80 -78
– -96
EMX5000-12/20
43