Electro-Voice CONTRACTOR PRECISION SERIES, Руководство по обслуживанию

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5
5. Function test
5.1. OUTPUT - offset voltage
DC-voltage measuring at the loudspeaker outputs CHANNEL A/B with U(DC)
≤
±10 mV.
5.2 LIMITER
5.2.1. Attenuation test
Both channels separately driven with a 1 kHz signal up to U(A) = 71 V (without load). Increase the input
voltage by 10 dB. The LIMITER LED lights and the output voltage ascents by approx. 0.6 dB to 76 volts, with
slight clipping. The distortion rate of the limited signal is at THD = 1 % … 2 %. Increasing the input signal up
to a value of +21 dBu should not result in remarkably higher clipping.
5.2.2. LIMITER FAST/SLOW-Test
•
tests have to be performed for both channels of the power amplifier individually: testing has to be
performed without load resistors connected.
1.) Drive the power amplifier with a burst signal (f = 1 kHz, 1-10 cycles, rate:
≈
0.5 sec.) and U(E) = +10
dB above the nominal input voltage.
2.) When monitoring the output signal via oscilloscope, continuously press the FAST/SLOW-switch.
• SLOW: after 2-3 signal periods, the limiter controlled the major distortion down to a minor residual
distortion (THD = 1 % … 2 %).
• FAST: already after 1-2 signal periods, the limiter controlled the major distortion down to a minor
residual distortion (THD = 1 % … 2 %).
When shipped, the appliance is set to SLOW!
5.3. POWER-ON DELAY:
Approximately 2 seconds after switching the power on, the relays E1 and E3 which are located on the printed
board assembly 86208/86212 and the relay E1 on the printed board assembly 84158 (channel A/B) pull
simultaneously.
5.4. FAN CONTROL:
Upon powering-on the power amplifier, the fans will run for approximately 2 seconds and stop when the power
amplifier has re-gained its "normal" temperature. In idling condition (power-on, no signal present) the fans are
switched between the SLOW and OFF mode, depending on the heat sink's temperature. When the switch S001
on the printed board assembly 86208/86212 is closed, the fans will run with FAST speed. When shipped, the
S001 switch is set to "OPEN"!
Connecting a variable resistor (approx. 50 k
Ω
) between CNBSERV 5 and CNBSERV 6 allows for testing the
functioning of the fans. During operation, CNASERV 6 can be utilized to monitor the temperature of the heat
sink.
FAN SPEED U(DC)
CNASERV 6
U(DC)
CNBSERV 4
Remarks
Stufe 0 < 6.5 V 0 V Fans are not running
Stufe 1 6.5 V ... 7.5 V 12.5 V
Stufe 2 7.5 V ... 9 V 19.5 V
Stufe 3 9 V ... 12.5 V 27.5 V
Protect > 12.5 V 27.5 V Power amplifier is switched off
5.5. SOAR-PROTECTION TEST:
Channels separately driven up to 56.6 V on 4
Ω
. Parallel connect a 0.1
Ω
resistor. The protection circuit reacts
and tries continuously to re-start! The protect-LED blinks in the same rhythm.
5.6. SHORT-CIRCUIT CURRENT-LIMITING TEST
testing has to be performed for both channels of the power amplifier individually:
- drive the channel with a burst signal (f = 1 kHz, 1-10 cycles, rate
≈
1 sec.) without load, with U(A) = 70 V
- connect a load resistor of 1
Ω
.
- the short-circuit current-limiter limits the output voltage at the load resistor symmetrically (monitor via
oscilloscope!) to a peak voltage value of 40 V ( approx. 40 A).
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