Ecler DPA2500T, Service Manual

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51-0153-0100 EP04-05-05 DPA2500T DPA4000T.doc 2 of 3
check with a millivoltmeter that at TP102 a 0dB gain level is obtained. If not, adjust R125. Once
channel I is fixed to 0dB, verify TP102 at channel II and proceed to adjust if gain level is not 0dB.
- Connect a 8
Ω
load impedance to the speakon-type BRIDGED output, and verify the achieved output
power levels:
3760W 173,4V for DPA4000T
2260W 134,5V for DPA2500T
Only channel I's input potentiometer should be active. Verify that the amplifier reaches its clipping
state without troubles. Return the unit to its STEREO operating mode.
- Connect a load impedance formed by a 4
Ω
resistor shunted to a 2µ2F capacitor, and apply a 1KHz
square waveform input signal. Using an oscilloscope, observe the output signal, and increase the
input signal level until the displayed signal starts clipping. At the flat level areas of the squared
waveform, only two or three ringing should be detected.
- Verify the SUBSONIC FILTER. Check the amplifier’s output level at 25Hz, is reduced in
4,5
dB when
comparing with the measured level without subsonic filtering. Leave the filter on the ON position.
- Verify the THERMAL protection circuitry. Short the LM35D thermal probe pins 1 and 2, and verify
that the relay releases and closes, while the
THERMAL and PROTECT LEDs indicators light up, as
the output signal is cutted off and the cooling fan increases its speed until it reaches maximum
airflow.
- Repeat this procedure on the other module.
PROTECTIONS
- Adjust the signal generator to deliver a 1KHz 0'8Vrms signal, and leave it ON.
- Turn down the power stage volume potentiometer to its minimum.
- Connect a 0,5
Ω
load impedance.
- Connect the oscilloscope test probes parallel to the load impedance. Select a 5V/div vertical scale,
and a 0'2ms/div time base.
- Turn up quickly the volume potentiometer. Depending on with branch is working, the positive or
negative half of the signal cycle is clipped. Verify that no ringing appear when the protection is
triggered.
- The output signal should be somehow similar to
the picture shown in the figure (from 15Vpp to
20Vpp). There are two protection circuitries,
one on the positive and another on the negative
branches of the unit. In case one of this
protections does not actuate properly, the
output signal will appear completely
asymmetric. The level of the half-cycle with is
not being protected will not be limited, thus
allowing to find out with branch is failing. It
could also happen that none of the protections
are triggered, this can be detected as the
measured signal levels delivered to the load
impedance are not being compressed. In case
this happens, immediately stop the testing
procedure. This may occur when the unit is receiving too low mains voltage (at least 240V, 250V
recommended), or if the signal level is increased too slowly through the potentiometer.
- After a period between 5 and 10 seconds is elapsed since the protection circuitry has triggered, the
module should switch over into PROTECT operating mode. This is, the relay closes, the PROTECT
indicator LED lights up, output signal is cutted off, and the 10 seconds lasting STANDBY cycle is
started.
- Wait until the STANDBY cycle ends, and allow the unit to repeat the process.
- Turn off the signal generator, output level set to minimum.