Adastra A121 User Manual Download Page 7

Troubleshooting 

No power LED on control panel 

Ensure IEC lead is in good condition and connected properly  
Ensure mains outlet voltage is same as voltage selector 
Check mains inlet fuse 
Ensure POWER switch is on 

Power LED is on but no other LEDs and no output 

Check input signals and condition of input connection leads 
Check MASTER, MIC or LINE controls are not turned fully down 
Turn down VOX control  

No output from condenser microphone(s) 

Ensure Phantom Power is switched on (turn Master down first) 

Power light and output LEDs lighting but no output 

Check speaker leads are in good condition and connected properly 
Check speakers are working (test on another amp if available) 

FM tuner drifts from programme channel  

Attach an FM antenna to the F connector on the rear panel 
Switch unit off and then on again (tuning may drift with temperature) 
Press CH- then PLAY/PAUSE to perform channel  store 

USB player will not play audio from media      

Press PLAY on transport controls 
Check memory device is connected properly (remove and re-insert) 
Check file types 

– standard compressed digital audio files required 

Check memory device works on a PC or Mac for standard playback 

Output is very loud or LIMIT LED is on constantly 

Check level of input signal is not too high 
Reduce channel volume and EQ settings 
Reduce MASTER level until LIMIT light stops flashing 
Ensure Hi-Z line level input(s) not connected via MIC1 or MIC2 

Output is working but at very low level 

Check input audio source level is not too low 
Increase channel volume and EQ settings if turned down 
Increase MASTER level 
Check for quiet recording of media files on USB  

Feedback (loud squealing or howling from mics) 

Face microphone away from speakers and monitors 
Reduce channel volume and EQ settings 
Reduce MASTER level 

Amplifier is getting very hot 

Make sure fans are working properly and not obstructed 
Ensure cooling vents are clear from debris and dust 
Check that 4Ω or 8Ω speakers are not connected to 100V terminals 
Ensure total 100V speaker wattage is not more than amplifier rating 
Ensure that 100V and 4Ω or 8Ω speakers are not both connected 
Ensure that total load across speaker jack outputs is n

ot less than 4Ω 

 

Note: for further troubleshooting, refer equipment to qualified service personnel for testing 

 

 

 

 

 

 

 

 

 

 

 

 

 

© Adastra 2011 

Summary of Contents for A121

Page 1: ...908 S251 Slave amp 250W 952 911 User Manual Features 2 Mixer amp models and 2 Slave versions Transformer coupled output for 100V or 4 16Ω operation USB FM audio player on mixer amp models Compact 1U rack mount format Dual fan cooled High efficiency toroidal transformers 32V phantom power switchable www avsl adastra com ...

Page 2: ...cover or obstruct cooling vents or fan grilles Placement Keep out of direct sunlight and away from heat sources Keep away from damp or dusty environments When rack mounting secure firmly in place and avoid positioning heavy items directly on top of the unit Ensure adequate access to controls and connections and pay attention to cooling air flow Cleaning Use a soft cloth with a neutral detergent to...

Page 3: ...250W system 100Vmax 250W 100V 2 5A so the speaker cable should be rated to 2 5A minimum Each speaker must be connected in a parallel chain and the total wattage for all speakers should not exceed 90 of the amplifier s rated output Please see the diagram below to show an example arrangement 25 FM antenna connection Cooling fans 26 OUTPUT 2 x RCA line output 27 LINE1 LINE2 2 x RCA line inputs 28 MIC...

Page 4: ...imum impedance of the total speaker load connected to either or both of these sockets must be no lower than 4Ω The impedance is calculated using an inverse calculation as shown below _________1________ _________1________ _________1________ Impedance Speaker 1 Impedance Speaker 2 Overall Impedance therefore for 2 speakers each 8Ω impedance _1_ _1_ _1_ 8Ω 8Ω 4Ω so the overall impedance is 4Ω for bot...

Page 5: ...via the OUTPUT pair of RCA connectors Operation With all volume levels and VOX control turned down connect the amplifier to the mains supply ensure correct supply voltage using a suitable IEC lead as supplied and switch POWER on HIGH and LOW EQ controls should be initially set to the vertical 12 o clock position If microphones are being used turn up the MASTER control approximately half way and gr...

Page 6: ...cking of the other channels when MIC channels are used SPECIFICATIONS Model A121 A251 S121 S251 Power supply Switchable 110 240Vac 50 60Hz IEC Output RMS 4Ω 120W 250W 120W 250W Mic input front MIC1 combo connector XLR jack N A N A Mic inputs rear MIC1 MIC2 6 3mm jacks N A N A Line input front AUX stereo mini jack 3 5mm N A N A Line inputs rear LINE1 LINE2 RCA pairs N A N A Mic controls MIC1 MIC2 L...

Page 7: ... file types standard compressed digital audio files required Check memory device works on a PC or Mac for standard playback Output is very loud or LIMIT LED is on constantly Check level of input signal is not too high Reduce channel volume and EQ settings Reduce MASTER level until LIMIT light stops flashing Ensure Hi Z line level input s not connected via MIC1 or MIC2 Output is working but at very...

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