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7 Valve Replacement
Important!
Do not attempt to change the KT120
output valves without reading these notes. Failure to
do so could be both dangerous to you and damaging
to the amplifier. Keep these notes handy.
Take care that you orient the valve correctly before
inserting. Line up the centre “Spigot” first. They are
easy to break, do not bend excessively to the side.
Health & safety; High voltages are present inside the
amplifier and on exposed valve sockets when valves
are removed, so take suitable care. It is not
necessary to remove the bottom cover. Beware
valves get hot in operation!
How do I know when to replace valves?
Generally speaking valve failure may be one of these:
1, The valve continues to work but the emission gets
low.
In the case of output valves this will result in not
being able to set the bias.
2, The valve gets noisy/microphonic.
Usually happens
to the small valves, can be confirmed by tapping with a
pen.
3, Heater fails.
No glow in centre of valve. Valve is cold.
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 at all.
4, Dramatic Failure.
Occasionally the demise of a
power valve may be obvious with internal sparks and
noise through the speakers. In that case, switch off and
do not use until a replacement is available. Before use
see chapter 6 “Bias Adjustment”. If there was any
associated burning smell etc, we would recommend a
qualified person examines the inside of the amplifier first.
If the amplifier sounds OK the valves are probably fine. If
the emission drops you will have difficulty setting the
bias for the output valves.
Valve life
will depend upon such things as hours of use
and number of on/off cycles, the Standby/HT Delay
Circuit if fitted will extend the life of the valve by not
stressing the cathode when it is cold. It is not good
practice to remove the valves unnecessarily as this can
strain the pins and cause tiny air leaks.
5, Changing valves:
If possible check the bias setting
before you attempt to change the valve(s), in order to
familiarise yourself with the procedure.
If changing all the KT120s be ready to adjust the bias in
order not to overload the power supply.
Don’t worry how
low the reading goes this will not cause damage. Do final
adjustment when the amplifier is fully warmed up.
If all is well there should be no more than a barely
detectable hum from the speakers, and the amplifier
should sound OK when tested.
6,
If you cannot set up 180mv bias, then the valve is
probably faulty or is unsuitable. (if the reading is zero the
individual fuse may be blown).
If the valves are brand new, you will need to check again
after approximately 10 & 100 hours, after that only
occasionally or if you suspect a problem.
7, To avoid damage to the amplifier and electric
shock hazard you must use only valves marked
KT120, KT88 (6550), 6SN7 (6N8/CV181).
Use only
valves which you know to be new or good condition
and test the amplifier thoroughly before resuming
normal use.
Ideally each amplifier will have a matched set of 4
KT120 valves.
Icon Audio have the facility to test and
match one or two valves to your existing set should
any fail.
8, Replacing the small valves:
6SL7 and 6SN7.
Neither of these requires any set up
procedure.
It’s just ‘plug and play’ although care
should be taken when removing and inserting not to
bend the pins. If this happens gently bend the pins
back into shape. (These valves are similar with the
same pin connection; accidentally interchanging
these two valves would not cause damage, buy may
reduce the amplifier performance).
Icon Audio are happy to check the valves/amp or re-
bias your amp free of charge.
8 Specification & Features
(Typical conditions @ 240v 50Hz)
•
KT120/88 output valves or eqv (6550)
•
6SN7 double triodes 1
st
stage and phase-splitter
•
Hand wired point to point components
•
No printed circuit board
•
No tag board
•
Ceramic valve bases for low noise/leakage
•
HT delay circuit to protect cathodes (optional)
•
150w RMS (KT120) Ultralinear
•
100w RMS (KT120) Triode mode
•
Signal to noise level -95db
•
Freq response 20Hz-20kHz +or- 0.5db
•
Power bandwidth -3db=10Hz-30kHz
•
THD 0.05% THD typical 10w 1khz
•
THD 0.5% THD typical 150w 1khz
•
Custom hand wound transformers using
Japanese long grain steel
•
Choke regulated power supply inc output
•
Supplied with attractive safety guard
•
Minimal feedback used
•
High quality oversized metal film & wire wound resistors
•
Audiophile High quality polypropylene audio caps
•
Internal wiring using silver gilt cable
•
Valves carefully matched for best performance
•
Gold plated Input & speaker terminals
•
950 mv sensitivity for full output 34.65v (High)
•
1.9 v sensitivity for full output 34.65v (Low)
•
230/240volts, 150watts (zero signal)
•
Standby switch function
•
3 amp T mains rear fuse (with spare)
•
1A ma AS KT120 anode fuses (with spares)
•
W:20cm. D:56cm. H:22cm. Weight:22kg
•
IEC mains lead, (5amp fused)
•
CE certified. ROHS & WEEE compliant
Specification subject to change without notice.
