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switched on when it is not in use. It is using
electricity and as valves have a finite life.
'Burning in'
Although the amplifier should sound good within
about 10 mins it can take up to an hour to sound
at its best and will take several months of regular
use before it is fully 'run in'.
Upgrading Valves!
Quality valves should sound better and have a
better service. The valves supplied with selected
models are the result of careful comparison with
other makes. But beware of paying a premium for
Amplifier Dead
Check the 3 amp mains fuse at the back of the amplifier.
To gain access, remove the mains lead. The fuse is in a
small plastic drawer, which forms part of the socket
assembly. To open insert a flat blade screwdriver or
similar and prise open. The fuse in use is the
innermost the outer is a spare. Should the replacement
fuse also blow there is a fault you should disconnect
from the mains and seek qualified help or Icon Audio.
Replacements should be 3 Amp 'anti-surge'.
The fuse in the wall plug should be a 3 or 5 amp fuse,
although unlikely to fail, this should be checked if the
amplifier fuse is OK.
There is also a HT fuse inside the amplifier. This
would not normally blow unless there is a valve fault
or an overload condition. This should be checked by
your dealer, or only if
Disconnect amplifier from the mains power and wait
20 minutes before removing bottom plate. If the HT
fuse has blown, there are replacements inside.
Replace bottom cover afterwards and check bias
immediately after switching on.
No sound
Have you selected the right input? Is the "Tape Monitor"
switch up? Are all the connections OK? Is everything
switched on? Are the speakers connected?
Distorted sound.
Could be your source, the speakers or the amplifier,
check all wiring, and try swapping things around to
eliminate or prove which component if the problem.
Left or right amplifier? If both probably the source unit.
Try another source. If one amplifier is distorted check the
bias. No bias reading means either a fuse blown or a
faulty valve. Distorted sound at higher volumes may be
because one of the output 845i valves is not working.
This could be due a faulty 845 or one of the MB845i
internal fuses blowing. A symptom of this would be no
0.4V bias voltage at the test point. Also the valve would
not be as hot as the others. Refer to an engineer or to
Icon Audio. Spare internal fuses are secured inside the
chassis. Replacements are available free of charge from
Icon Audio.
Hum Problems
See also section 6
If you experience hum, try disconnecting all inputs, if
hum persists this is probably an amplifier fault.
If not, identify which input is causing hum. Connect one
input at a time. A common cause is a 'hum loop' caused
by having too many earths, and may be identified by
unplugging each input source from the mains. One
remedy for this is to use an interconnect which only has
5 Trouble Shooting
you feel competent.
"New Old Stock" valves where you may be paying
for rarity value and not performance. Icon Audio
normally keep a range of upgrade valves in stock.
Cabinet Care
To remove dust we suggest gentle brushing of the
polished stainless steel cabinet with a soft
paintbrush. Other marks can usually be removed
with a damp cloth. The Perspex valve cover may
need a gentle wipe with soapy water and drying
with a duster. Never use anything wet on the
amplifier, and always clean with the power
disconnected.
the screen connected at one end. Other causes of
low-level hum can be from adjacent equipment, so
experiment with moving equipment around to see if
this makes the hum better or worse.
Strange noises coming from speakers
Turn volume to minimum on unused input, if the
noise disappears, the fault is with the source or the
connection. If noise persists, the problem is with
amplifier.
If the whole output valve glows red (other than the
heater), often accompanied by a hum through the
speakers, switch off immediately, and refer to Icon
Audio or a service engineer, as this could be valve
failure.
Service: Should you suspect a problem, you could
return the unit to your dealer or Icon Audio for a
periodic service or return the valves for testing free of
charge. You should carefully remove the valves (the
845s should be held by the base when removing, to
prevent damage) numbering them with a marker from
left to right as you do so in order that that may be
replaced in the same position. They should be well
packed in cardboard & foam or similar, and returned
to Icon Audio for testing. (Valves are very rugged if
packed properly).
Mains Supply
This amplifier is hard wired to work on 230/240v ac.
The transformer may be re-configured for 110/120v
ac by a qualified engineer. Contact for more
information.
This manual is provided for guidance only, and is not
intended as a comprehensive service manual. In
case of problems you should refer to your dealer or
directly to Icon Audio.
Page 6
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