51-0098-0100 EP14-02 Anglès.doc 1 of 4
PRELIMINARY:
- Check the Ground Link switch.
- Be sure that the correct cable types are used.
- Main POWER switch OFF.
- Select a 1KHz 0dB output signal on the generator, but keep it turned off.
- Place four 4Ω load impedances into outputs 1, 2, 3 and 4. If it’s not possible, just place
one 4Ω load into the tested channel output.
- Connect the millivoltmeter and the oscilloscope to channel one.
- Turn down all potentiometers to their minimum position.
- Connect the power amplifier’s mains plug to a 230Vac variac output.
VERIFICATION:
- Retire fuse F101 (or its matching fuse on any other tested channel), placed at channel
one’s +Vcc. In its place, insert a 10 A ranged DC ammeter.
- Connect the power amplifier mains plug to the variac output, turned down to deliver 0V.
Switch over the unit’s main POWER switch to ON. Slowly increase the variac’s output
until it reaches 230V output voltage, and verify that the current consumption adjustments
remain correct: 150mA. If this value has changed, rectify it. Once adjusted, seal the
potentiometer with fixing lacquer.
- Retire the ammeter and replace instead the F101 fuse. Caution! The unit’s power supply
will be charged! Previously the power supply should be properly discharged, or disconnect
the module’s power supply wires (yellow-, black- and brown-colored wires) to avoid
electrical shocks. Repeat this procedure on all other channels.
- Once the current consumption is checked, switch off and again on the unit with its main
power switch, verify that the green neon lights up, that the unit first remains for 10
seconds in STANDBY mode and that the cooling fans run up to maximum speed.
- Apply a 0dB 1KHz signal to XLR-type input 1, by turning on the signal generator.
- Connect a 4Ω load to this channel’s output.
- Verify the unit’s output power when working at nominal mains voltage (230Vac).
Vo=41Vrms (millivoltmeter)
- To verify the ANTICLIP function, increase the input signal level above 0dB and check that
the clipping output signal is smoothened. Place a mini-jumper into the test point terminal
near the VTL5C8 device, verify that the anticlip function now is triggered earlier and
rounds the clipping signal even more. Check the CLIP indicator LED’s are lit, and, when
reducing the output signal level in 0’5 or 1dB, the CLIP LEDs turn off. Leave the mini-
jumper inserted.
- Verify the unit’s bandwidth curve, which, with a 2KHz 0’5V input signal, should be linear
between 20Hz and 20KHz without inducing any distortion to the output signal. Also check
that when applying an input signal up to 50KHz, the unit’s output level only decreases in 1
or 2 dB, and no visible distortion is observed.
author:
J. Colomines
date:
021007
project:
EP14-02
product:
MPA4-400
E
C
LE R
approved:
num:
51.0098
version:
01.00
title:
VERIFICATION PROCESS
(44 strony)
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