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7 Valve Replacement
Important!
Do not attempt to change the 805
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.
USE ONLY 805 WITHOUT TOP CAP.
6SN7 Pull gently but firmly to remove. Take care that
you orient the valve correctly before inserting. Line up
the centre "Spigot" first. They are easy to break.
2A3 Pull gently but firmly to remove. Has 4 pins two
are larger than the other. Please note the positioning
before insertion.
805 Twist anti-clockwise 45 degrees to remove. Insert
by locating pin in slot and rotating clockwise about 45
degrees.
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 properly.
2, The valve gets noisy/microphonic. Usually happens
to the small valves, can be confirmed by tapping with a
pen, and swapping a valve from the same position in the
other amplifier.
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. It is not good practice to
switch the amplifier on and off unnecessarily, or by
removing the valves unnecessarily as this can strain the
pins and cause tiny air leaks.
5, Changing valves:
Before changing the 805 valves ensure that it safe to do
so by switching off and removing the mains plug at least
20 minutes beforehand. This will enable dangerous
voltages to dissipate, and the valves to cool down.
If possible check the bias setting before you attempt to
change the valve(s), in order to familiarise yourself with
the procedure.
If changing both 805s, be ready to adjust the bias in
order not to overload the power supply. Don't worry how
*See engineers notes at rear
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. Note that only 805
valves are compatible with the amplifier, 845, 211
and similar looking valves will damage the amplifier,
and will be dangerous.
6, If you cannot set up 400mv, then the valve is
probably faulty or is unsuitable. (If reading zero the
HT fuse may have 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
805, 2A3, 6SN7 or equivalent. Use only valves
which you know to be new or good condition and test
the amplifier thoroughly before resuming normal use.
8, Replacing the small valves:
The 2A3 will require bias adjustment as it controls
the 805. The 6SN7s do not require any set up
procedure. It's just 'plug and play'.
Icon Audio is happy to check the valves/amp or re-
bias your amp free of charge.
8 Specification & Features
(Typical conditions @ 240v 50Hz)
•
805 Triode output valves
•
2A3 Triode driver valve
•
4x 6SN7 double triodes for first stages (CV181)
•
Hand wired point to point components
•
Ceramic valve bases for low noise/leakage
•
40w RMS at clipping 1kH
•
Signal to noise level -95db
•
Freq response 20Hz-20kHz - 1dB
•
Power bandwidth -3db=10Hz-30kHz
•
0.3% THD typical 8w (0.1% 1w) 1khz
•
Custom hand wound transformers using grain
oriented steel
•
Supplied with attractive valve cover
•
Minimal feedback used
•
Audiophile oversized metal film resistors
•
Audiophile High quality polypropylene or Jensen
audio capacitors (optional upgrade)
•
Internal audio cable using silver plated PTFE
•
Valves carefully matched for best performance
•
Gold plated Input & speaker terminals
•
400 mv sensitivity for full output (High)
•
1v sensitivity for full output (Low)
•
5 amp T mains rear fuse (with spare)
•
250ma F 805 ceramic anode fuses (with spares)
•
W: 24cm. D: 57cm. H: 28cm. Weight:35kg
•
230-240v AC 50-60 Hz (or 117v for US)
•
IEC mains lead, (5amp fused)
•
CE certified. ROHS & WEEE compliant
Specification subject to change without notice.
Page 8
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