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*See engineers notes at rear

  

 

Page 

10 

Engineers Notes 

 

These notes are only intended for use by an 
engineer qualified to work with high voltages found 
in valve amplifiers. Owners should refer any 
problems to a dealer or service agent.  
 
The amplifier may be inverted by supporting the 
transformers on non abrasive surface (e.g. dense 
foam, books etc) which allows space between the 
KT120 and the work surface. 

 

Safety 

Before removing base disconnect the power cord. 
Always allow 10 minutes for the HT to discharge, or 
measure before proceeding. If possible use a bleed 
resistor of around 5-10K

 will speed this up, and 

check that the HT voltage has discharged.  

 
Amplifier dead. 

Check the 20mm mains fuse in the IEC socket at 
rear of the amplifier, if dead there is a spare 
included. Or the fuse in the plug (if applicable). If 
not either check in-line power switch fuse adjacent 
to IEC socket. 
 

230v to 115v Conversion. 

Take the precautions as above. It is necessary to 
change the primary power windings from series to 
parallel. This can be achieved by unsoldering the 
“live” input from the IEC socket and replacing it with 
the two “centre tap” connections normally found 
insulated with “heat shrink”. The single removed 
wire should be connected together with the “neutral” 
connection on the IEC socket. A The IEC socket AC 
fuse should be doubled in value. 

 

 
 

Summary of Contents for MB30m

Page 1: ...out anything please contact your dealer or one of our team Valve amplifiers do need a little more attention than their solid state counterparts but the sonic results are well worth it In this manual we have tried to include everything that you need to know Please let us know if you find any errors or feel that we have missed anything out The MB30m is a Single Ended one output valve triode UL power...

Page 2: ...libration ma Run min 10 hour test Check input Output Valve Bias level v Sound Quality Channel Balance Valve Microphony Valve Seating Hum level L R mv RF Test LED brightness Serial No sticker and recorded Mains voltage 110 120 230 240V IEC Mains Fuse A Soft Start Fitted N A Sales invoice Bottom label Credit card receipt Customer survey form Bias meter Transformer Protection N A Upgrades Output valv...

Page 3: ...sensitive to noise so therefore may be placed close to each other similar to a conventional power amplifier Or alternatively place adjacent to each loudspeaker in order to keep the loudspeaker cable to a minimum They should be placed on a flat surface to allow a gap underneath to aid ventilation ...

Page 4: ...eutral terminal and Green Yellow to Earth terminal 6 SWITCH ON The meter should light up and a visible glow may be seen inside the valves when viewed from certain angles After about one minute the amplifier should now be working With the pre amp volume control set to minimum there should be no sound coming from the speakers except a barely discernible hum If there are any unpleasant sounds coming ...

Page 5: ...t of phase with the sound stage inside out with reduced bass If you are unable to check this or confirm the polarity e g if you have built in wiring a test disc will be helpful If you are bi wiring you can independently use either 4 or 8 ohms for the bass and treble Many modern smaller speakers use a 4 ohm unit If in doubt the heaviest base is the best match depending upon preference and again 4 o...

Page 6: ...gher volumes may be because one of the KT120 valves failing A symptom of this could be unable to bias properly Refer to an engineer or to Icon Audio 3 Hum Problems If you experience hum try disconnecting the input if it clears it is NOT the amplifier but some cause external to the MB30m and further advice should be sought from your dealer or Icon Audio By elimination find out which unit is causing...

Page 7: ...d box with a note detailing the problem which valves you suspect and your contact details We will then contact you with the test results Possible visible valve faults Not all valve faults are visible but KT120s 6SN7s and GZ34s valves should not be used if 1 The silver getter material has turned white or is disappearing air leak 2 The valve rattles excessively a slight rattle is normal 3 There are ...

Page 8: ...lease contact us first 8 Specification Features 100 Pure Class A output power Class A all Triode front end KT120 60w beam pentode output valve 6SN7 CV181 double triodes 1st stage valve Valve rectifier GZ34 5AR4 Output power Triode 16w 11 35v 8 Ohms Ultralinear 27w 14 7v 8 Ohm Oversized choke regulated power supply for both driver and output stage Our own unique designed tertiary wound output trans...

Page 9: ...omestic hi fi use It is not guaranteed for commercial Public Address use or use in other situations The guarantee becomes void if the unit has been modified in any way not approved by Icon Audio 10 Packing Instructions It is essential that the original box and packing be kept in good condition as this provides vital protection from damage during transit Please do not write on box but use removable...

Page 10: ...istor of around 5 10KΩ will speed this up and check that the HT voltage has discharged Amplifier dead Check the 20mm mains fuse in the IEC socket at rear of the amplifier if dead there is a spare included Or the fuse in the plug if applicable If not either check in line power switch fuse adjacent to IEC socket 230v to 115v Conversion Take the precautions as above It is necessary to change the prim...

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