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sound, but depending upon your set up, you may
hear no difference. The gain on the volume
control remains the same, so no difference will be
noticed in volume. But the maximum will be half.
As
switching
will
transformers
it
triode/Ultralinear switching be done when the
amplifier is switched into standby mode.
DO NOT LEAVE SWITCHED ON 24/7
Whilst the amplifier will sound at its best when it is
properly warmed up, there is no advantage
leaving it switched on when it is not in use. It is
using electricity and valves have a finite life of
very roughly 5000 hrs WHICH IS ONLY SEVEN
MONTHS CONTINUOUS USE! (Or 4½yrs at 3
hrs a day).
Conversely the valves and other
components are stressed more at switch on;
therefore do not switch on and off unnecessarily.
We would always advise that any item of home
electronics is switched off when not in use
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
bade 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. Replacements should be 3 Amp
'anti-surge'.
The fuse in the mains plug should be a 5 amp,
although unlikely to have failed, this should be
checked if the amplifier fuse is OK.
No sound
Have you selected the right input? Are the
connections OK? Is everything switched on? Are
the speakers connected?
Valve Fuses/Distorted sound.
Each pair of KT88/KT120/KT150s are protected
by a 500ma "T" (anti surge) fuse. If the left or right
fuse has blown there will be no sound on that
channel. You can test for this by checking the
bias; a zero reading would normally mean a blown
fuse. Also the valve(s) in question will be much
cooler (to the touch, be careful!). Replacement will
require the amp inverting on a soft cloth and the
bottom removed. Ensure that power is removed at
least 10 mins beforehand. Only replace with
correct type, (available from Icon free). Only
attempt if you feel confident, or contact your
dealer or Icon for assistance. Should the
replacement subsequently blow, this usually
means the valve is faulty, or possibly a fault
elsewhere.
2 spare fuses are normally "taped" to the
inside bottom plate).
Hum Problems (through speakers)
If you experience hum, try disconnecting all
inputs, if hum persists this is probably an amplifier
fault. Check bias or refer to Icon Audio.
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,
stress
the
output
is
important
that
7 Trouble Shooting
'Burning in'
Although the amp 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!
Good quality valves should sound better, and
have
a
good
service
performance and be reliable; the last three items
will make a valve sound better longer. The
upgraded valves supplied with selected models
are the result of careful comparison with other
makes.
Cabinet Care
To remove dust we suggest gentle brushing of the
paintwork etc, with a soft paintbrush. Other marks
can usually be removed with a damp cloth.
On no account use anything wet on the amplifier,
and always clean with the power disconnected.
and may be identified by unplugging each input
source from the mains. One remedy for this is to
use an interconnect which only has 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.
Some premium interconnects are NOT screened,
and will therefore hum. These are not suitable for
use with the ST60 MK IV as they may pickup
noise.
One channel missing.
Usually 'bad' connection on either the input or the
speakers. Try swapping the connection over to
establish if the cause is:
(a) Input to the amp.
other channel.
(b) Amplifier or speakers.
move.
Strange noises coming from speakers
Turn volume to minimum on unused input, if
problem corrected either fault with source unit or
with connection. If noise persists, problem with
amplifier.
If a 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, which if neglected may cause other
damage.
A valve that is lit up is not a guarantee that it is
working properly; conversely a valve that is not lit
up will not be working.
Valve Replacement (see also section 9)
Valve life will depend upon such things as hours
of use and number of on/off cycles, the HT Delay
Circuit if fitted will extend the life of valves by not
stressing them when cold. It is not good practice
to remove the valves unnecessarily as this can
strain the pins and cause tiny air leaks.
Service: Should you suspect a problem, you
should return the unit to your agent/dealer or Icon
life,
maintain
their
Sound will move to the
Sound
will
not
Page 6
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