Octave JUBILEE MONO SE, Owner'S Manual

Page: 23 / 31

21
6. TUBES
6.2. General procedure for changing tubes
Only qualified personnel should replace tubes.
General procedure:
Switch the amplifier off and disconnect the plug
from the mains supply. Allow it to cool down for
10 minutes.
1. Remove the protective grille.
(see chap. 6.4.1)
2. Remove the old tubes by carefully pulling
out them upwards.
3. Fit the new ones.
Insert the power tubes into their
sockets as shown on the tube layout.
Ensure that you correctly locate the
anti-rotation lug on each of the tubes.
.
Anti-rotation recess
on the tube socket
Adjustment after the tube changing
New driver tubes
Replacement driver tubes require no adjustment.
New output tubes:
1. When you have successfully
replaced the necessary tubes,
replace the grille and panels.
2. Before you switch the amplifier back on
after fitting new output tubes, turn the
bias
adjustment control regulators
counter-clockwise toward minus as far as
it will go.
The control is a ten-turn
potentiometer, i.e. it takes ten revolutions to
go from the maximum to the minimum
setting.
3. Switch the amplifier on, carry out the
checks described in chap. 3, and adjust the
bias as required.
4. Your amplifier is now ready for use.
Depending on the type, age and
manufacturer of the tubes, you may need to
readjust the settings in the first few weeks.
6.3. Tube service life
 Thanks to the protection circuits and soft
start electronics, the output tubes used in
your amplifier should achieve an average
service life of 3 to 5 years. We cannot,
however, guarantee the service life of the
tubes. These are average values, which will
vary with the type and manufacturer of the
tubes.
The internal protection and soft start circuits
cannot prevent tube faults. They are
designed to minimize the stress on the
amplifier and to protect it should a fault
develop. You can select tubes by
measuring their characteristics but this
does not guarantee that they will last for a
long time. Indeed, it is impossible to predict
how long the output tubes will last.
A well-made tube has a life expectancy of
between 3 and 5 years. However, it remains
impossible to detect certain weaknesses in
the structure of a fully functional tube. The
protection circuits in the power amplifier will
also protect the unit against the damage that
a defective output tube could cause.
 Driver tubes can last for 10 years or longer.
 Because tubes have different service lives,
you will never have to renew the entire tube
complement at the same time.

Please note that some tubes need a long
time (up to 300 hours) to achieve their
optimum sound quality.