Electro-Voice CPS 1, Руководство по обслуживанию, Страница: 5 / 18

3
- 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 35 V, respectively 27 V ( approx. 35 A
respectively 27 A maximum peak output current).
5.7. DC-VOLTAGE PROTECTION CIRCUIT TEST
separately test both power amplifier channels:
- drive the power amplifier with a test signal (f = 7 Hz) and without load
- at an input voltage of approx. 3 Vpeak the protection circuit reacts and tries continuously to re-start!
The protect-LED blinks with the same frequency.
- Repeat the test with f = 14 Hz; the power amplifier should not switch off.
5.8. HF-PROTECTION CIRCUIT TEST
Caution: it is mandatory to drive the power amplifier without load resistors connected.
Drive the power amplifier with a +20 dBu sine burst signal (40 mS ON, 960 mS OFF) f = 100 kHz applied to
each channel at a time. The protection circuit should react. The power amplifier tries to re-start continuously.
The PROTECT LED blinks with the same frequency.
Repeat the test with
f = 50 kHz ; the power amplifier should not switch off.
5.9. LED INDICATOR TEST
Apply a 1 kHz sine signal and increase its level. At approximately -30 dBu the SIGNAL LEDs will light and at
about +1dBu the LIMIT LEDs light.
6. Level CHANNEL A B
6.1. voltage amplification
Unit Input U(E) Measure point U(A) Load resistor Test
frequency
CPS1 CH. A/B 1Vrms SPEAKER A/B 42V
∞
1kHz
CPS1 CH. A 1Vrms BRIDGED OUT 84V
∞
1kHz
CPS2 CH. A/B 1Vrms SPEAKER A/B 49V
∞
1kHz
CPS2 CH. A 1Vrms BRIDGED OUT 98V
∞
1kHz
6.2. MAXIMUM INPUT LEVEL: U(E) = +20dBu
7. GROUND LIFT switch
The circuit ground (at the input or the output connector) is measured versus the common ground of the
enclosure (contact at the ground terminal, located on the rear panel - or common ground of the mains cord).
position of the switch:
GROUNDED : R = 0
Ω
UNGROUNDED : R = 5
Ω
8. Amplitudes - non-linearities
- testing with load resistor 8
Ω
, dual mode
- MDW = 80 kHz
Measuring at nominal output remarks
CPS1 CPS2
THD+N ( f = 1kHz ) <0.05% <0.05%
IMD-SMPTE
<0.08% <0.08% 60Hz, 7kHz
DIM 30
<0.03% <0.03% 3.15kHz, 15kHz
9. Frequency response
the frequency response is linear. (please take the cut-off frequencies into consideration)
low cut-off frequency high cut-off frequency
-3dB fu < 10Hz fo = 110kHz
-1dB fu < 10Hz fo = 57kHz