Page 7
7 Valve Replacement/Problems
Valves are semi-consumables rather like the tyres on a
car or the stylus on a turntable. Most problems with the
amplifier will be valve related. If the amplifier sounds OK
and the bias voltages on the output valves are OK then
the amplifier is probably best left alone.
Likely reasons for valve failures include: (i) heater stops
working = cold valve. (ii) internal short = valve glowing or
arcing with noise from speakers. (iii) air leak = valve
glows blue inside and noise from speakers. And the
“silver” coating may turn white (iv) intermittent with any of
above. (v) loss of emission over time with consequent
power loss (usually over a long period of time). But this
is not a comprehensive list.
The most common problem with the small valves is
when they become excessively microphonic. This can
usually be identified by tapping with a pen. Sometimes
they can go “noisy” rustling/spitting/hissing. The small
valves are double triodes,
so you should see a “double
glow” inside. We are able to provide telephone
assistance with valve problems. And can test and supply
single valves to match up with a relatively new matched
set.
ALL SUPPLIED VALVES ARE TESTED IN THE
SAME/SIMILAR UNIT BEFORE DESPATCH TO
ASSURE YOU OF THE BEST QUALITY/RELIABILITY!
Important!
Do not attempt to change the output
valves without reading these notes. Failure to do so
could be both dangerous 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.
Should you accidentally break a spigot on a valve, return
to Icon with the broken piece(s). We can normally repair
this for £5 plus £2 P&P (UK),
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!
Changing valves:
If possible check the bias setting
before you attempt to change the valve(s), in order to
familiarise yourself with the procedure.
Use good quality matched output valves. This will stop
wide variations in bias voltage. Matched sets and odd
replacement valves may be obtained from Icon Audio.
If changing all the output valves be ready to adjust the
bias in order not to overload the power supply. Do not
allow the reading to go above 12v.
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. If the valves are not
matched the highest reading valve should be limited to
10v
6, If you cannot set up 8v, then the valve is probably
faulty or is unsuitable. (if the readings are zero on one
channel, the HT fuse for that channel may have blown,
two spares are inside the chassis).
7, To avoid damage to the amplifier and electric
shock hazard you must use only valves marked
6L6/EL34/6CA7/KT66/KT88.
Use only valves which
you know to be new or good condition and test the
amplifier thoroughly before resuming normal use.
Kt120/150 ARE NOT SUITABLE as the higher heater
current will overload the power transformer, and risk
of failure, (not covered by the warranty).
8, Replacing the small valves:
6SN7 (outside pair) 6SL7 (centre)
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; accidental
wrong insertion would not cause damage, or you
could change them round for test purposes).
Unnecessary removal and insertion is to be avoided
due to the formation of micro cracks around the pins.
Icon Audio are happy to check the valves/amp or
your re-bias your amp free of charge.
8 Specification & Features
(Typical conditions EL34 valves@ 240v 50Hz
. 8 Ω)
•
6L6/EL34/6CA7/KT66/KT88 output valves
•
6SL7 double triode for first stage
•
6SN7 double triode phase-splitter
•
Hand wired point to point components
•
No printed circuit board
•
Ceramic valve bases for low noise/leakage
•
HT delay circuit to protect cathodes (optional)
•
30w RMS per channel Ultralinear (EL34)
•
15w RMS per channel Triode (hardwired option)
•
Dedicated headphone transformer winding
•
Signal to noise level -90db
•
Freq response 20-20khz +0 - 0.5db 1W
•
Bandwidth 10Hz (0db) -55kHz (-3db) (12.5W)
•
Bandwidth 18Hz
– 62kHz -3db (25w)
•
0.2% THD
•
Custom hand wound transformers using
Japanese long grain steel
•
Supplied with attractive safety guard
•
Minimal feedback used
•
Audiophile high quality oversized resistors
•
Audiophile High quality polypropylene audio caps
•
Japanese ‘Blue’ ALPS volume pot.
•
Internal wiring using silver PTFE audio cable
•
Valves carefully matched for best performance
•
Gold plated Input & speaker terminals
•
3 line Inputs for CD, Tuner, Phono etc
•
Gain= 70 (8ohms)
•
250 mv sensitivity for full output
•
230/240volts, 180watts (max signal)
•
Internal fuse 2x T250ma ceramic
•
Fuse T1.6TA (230v) (T3A 117v) anti surge
IEC rear socket fuse (with spare in fuse holder)
•
UK mains plug fuse 3A
•
320W, 310D, 230H, 23kg
•
IEC mains lead, (5amp fused, UK mains lead only)
•
CE, ROHS & WEEE compliant
Specification subject to change without notice.
