AUDIO TELEX AT250B User manual

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Aud io Telex*C*omfl5n:S"?fjons Pty Ltd

AT250B Power Amplifier
Product Description
The AT250B is a 250 watt po\rer amplifier with outputs fu 4 olrns, 70 and 100 volt line. It may be desk m rack mqmted but
cmes gandard as self standing with rutrber feet. The AT250B featrres a flat ssewdriver acc€ssible gain curtol m the fimt panel
and a limit indication LED. The frctory setting for the front panel gain cmtrol is I volt RMS. Units may be stacked to a maximum
of3 uitshigh.
Front Panel Controls
l. Galn Gontrol: Access is via the front panel using a small flat head screwdriver. Factay pre-set is 1 volt RMS, the
sensitivety of the amplifier may be reduced by turning the gain c,mtol in a counter-clockwise direction, or increased by turning
the pin cqrtrol in a cloclnrise directim .
Llmlt LED: This red LED is desigred to give the user a visual indication of the status of the operating oonditim of the
amplifier and is integral to the inbuilt prdectior included in the amplifier. Dring ncmal qleratim, the LED will flicker
oocasiurally, however if the LED flickas fm lemglhy p€rids m stays cmtinuorsly glolying; this is an indicatiqr that the
amplifier is being overdriven by the incming program sipal. If this input ovenload cmditim is cmbined with the maximum
load m the output of the amplifier then the amplifier will autmatically shut itself dffi'n fc a period of approximately 3 secmds
and then turn itself back on agein and continue to cycle in this frstricr until the abnormal cmdition is removod. This is a feature
of the amplifier and is desigred to prdect the internal circuity of the amplifier and also to prdes{ aoy speakers that may be
cmnected to the ortput of the amplifier.
Power Button: This switch cqrtols the switching of AC power to the anplifier. Roc{ring this switch upwards turns on
AC power to the amplifier while rocking the switdr downwards tums pourcr of to the a.mplifier. When in the upward position,
the red nem in the body of the switch will glow.
3.

l.
Rear Panel Connections
a
a
a
a
a
a
3 Pin IEC talns Power lnlet The operating voltage is 240 VAC @ 5OIIzor ll0 VAC @ ffiIlz. The AC power
voltage level is nd externally user adjustable hS is factory pre-set. The inlet is equipp€d with an inbuilt AC fus€ holder fitted
with a 6 amp fuse plus a spare fouod lrithin the holder. Power cursumptior is 400VA. g Pbasc ensune that the meins
powcr cord is disconnectcd bcforc attempting to check or rcphce thls frsc.
DireCt OUtpUt Terminal Stfip: These screw terminals allow access to the diroct outputs of the amplifier. Reading
frm left to right the terminals are-
LowlnpedanceCmmqr
4 Ohms
Spare
Csrstant Voltage Cmmm
70 VoltLine
lffiVoltLine
Twin DC fuse receptacles: Access the DC fuses is by tuming the cap half a turn conrter-clockwise with a
screwdriver. The value of the fuses is 8 Amps slow blow. I Ptcasc ensurc thrt the AC power switch is in thc 'of lnition
and thrt thc mtins power cord b disconnected beforc attemping to check or rephce this frsc.
+. Signal lnpUt SOCketS: Signal input to the AT250B is via a 3 pin )(LR sockc and is rated at lOK Ohms and is active
baland. The two sockets provided atre are bridgd for inlout cmnoctiqr. Pin cmnestiors are Pin I - Earft. Pin 2 : Active
Positive (+). Pin 3 = Active Negative (-).
Fuse Sizes
tains 240 VAC: 6Amperes SlorvBlow
DC: Z x I Amperes SlowBlorv
Notes
I There are no user adjusable controls inside the amplifio so the cover shotrld srly be removed by qualified service persurnel.
all cases the mains power lead should be discqrnected befoe the cover is removed.
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AUDIO TELEX COMUNICATIONS PTY LTD SYDNEY AUSTRALIA