3
5.2.3. Attack- and release times
separately testing the power amplifier channels is mandatory:
Test has to be performed at the Direct Output
without load.
1.) Drive the power amplifier's input with a burst signal (f = 1kHz, 10 cycles, rate : 3 sec.) and U(E) = +10dBu.
2.) Monitor the output signal via oscilloscope. After 1 - 2 signal periods, the limiter has reduced the major
distortion to a minor residual distortion (THD
≤
1%)
attack time: approx. 2 ms
release time: approx. 130 ms
5.3 POWER-ON DELAY
Feed the test signal to the power amplifier input. Switch the power amplifier ON using the "Power On" switch.
Approximately 2 seconds after pressing the "Power On" switch, the signal is present at the output.
5.4 POWER REMOTE
Switch the power of the appliance OFF. Feed a control voltage of +24V to the Power Remote input. The power
amplifier has to start operation and after disconnecting the control voltage has to go off again.
5.5 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. Connecting the CNS1.8
via a 5k
Ω
resistor to +15V lets the fans run in SLOW mode. A FAN VOLTAGE of 16.8V DC can be measured
between pin CNS2.4 and pin CNS1.4. When disconnecting CN5, the fans will run in FAST mode. A FAN
VOLTAGE of 28V DC is measured between pin CNS2.4 and pin CNS1.4.
5.6 SOAR-PROTECTION TEST
Channels separately driven up to 0dB via the Direct-Output, terminated with 4
Ω
. Parallel connect an 1
Ω
resistor.
The protection circuit reacts and tries continuously to re-start! The protect-LED lights.
5.7 SHORT-CIRCUIT CURRENT-LIMITING TEST
separately testing the power amplifier channels without load is mandatory:
-
drive the channel with a burst signal (f = 1kHz, 1-3 cycles, rate
≈
1 sec.), at the Direct Output with
U(E) = 0dBu.
- 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 15V or 20V respectively (approx. 15A or 20A respectively maximum
peak output current).
5.8 DC-voltage and HF-Protection Circuit
- Testing the protection circuitry against the occurrence of DC-voltage and HF at the output is only possible
directly via the Main PCB when it is not installed in the appliance.
5.9 INDICATORS TEST
Feed a 1kHz sine signal while slowly increasing the level. At approx. -30dBu the SIGNAL LEDs will light and
at approx. +1.5dBu the Limit LED will light.
