AUSTRALIAN MONITOR AMIS250 Series, Руководство по обслуживанию

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AMIS250
Circuit Description
The AMIS250 mixer amplifier is designed for commercial installations. It operates on [230/240 VAC,
50Hz] (240V version)/[115VAC, 60Hz] (115V version) and may be desk or rack mounted (rack mount kit
supplied). The AMIS250 delivers 250 watts into a load of 4 ohms, [70 or 100 volt line] (240V version)/ [25
or 70 volt line] (115V version). As standard, the AMIS250 is supplied self standing with rubber feet. It
features 6 microphone/line input channels as well as a host of unique features including multiple levels of
muting and 24 VDC make the AMIS250 a very flexible amplifier. [The 115V version also has a
transformer balanced, 600 ohm telephone input] (115V version).
Power Switch
This switch controls the switching of AC power to the amplifier. A blue ‘On’ LED will indicate whether
the amplifier is switched on or off. This switch will not switch DC power on or off in DC operation. In DC
operation mode, the amplifier is always on and the blue power LED will always be illuminated.
Protect LED
A feature of the AMIS250 is high temperature protection. In most applications, the internal cooling fan will
most probably never switch on. When used with demanding speaker loads or in difficult operating
environments, the fan may regularly switch on to cool the amp down and then switch off again. This
switching on and switching off is quite normal. The “Protect” function is there to protect the amplifier from
high temperature problems which would only occur if the fan stopped working or became clogged up. In
this very rare occurrence, the amplifier will shut down and the protect LED will illuminate. The amplifier
will automatically restart once it’s internal temperature has fallen below the fan switch on temperature.
The fan switch on temp is preset at 60degC by the trimmer on the power amp board R58 (10k) and the
NTC R25 (10k@25degC).
The high temperature trip point is set at the factory by trimmer R58. Turning the trim pot clockwise will
cause the amplifier to trip and mute at a lower temperature.
AC Power Inlet
The operating voltage is [230/240 VAC @ 50 Hz] (240V version)/[115 VAC @ 60Hz] (115V version). The
3 pin IEC power inlet is located on the bottom left of the rear panel and accepts a standard mains power
lead fitted with an IEC connector. Before plugging in a power lead, please check the rear panel of the
amplifier to ensure that the voltage switch is set correctly for your part of the world.
The inlet is equipped with an in-built AC fuse holder fitted with a [6.3 amp] (240V version)/[8 amp] (115V
version) fuse plus a spare within the holder. Power consumption is 550 VA.
24 Volt DC Power Inlet
The AMIS250 features optional 24VDC power to run off a battery supply if required. This is connected via
the rear terminal strip. The front panel Power Switch will not switch DC power ‘on’ or ‘off’ in DC
operation. In this mode the amplifier is always ‘on’.
[230V/240V Slide Switch] (240V version)
The operating voltage of the amplifier is user selectable between 230V and 240V via a slide switch located
on the right of the AC inlet. This switch should be set to match the AC voltage of your country. The mains
transformer is wound with a 230V winding plus a 10V winding internally connected.
Power Amp
The power amp is a push pull single supply amplifier driving a centre tapped transformer. The amplifier
has an overall gain of approximately x10 and the transformer has a turns ratio of approximately [x7] (240V
version)/[x5] (115V version). The sensitivity of the amp is approximately 2.7V.