When to
Replace Tubes
Normally, vacuum tubes slowly deplete themselves over their lifetime.
When their power dissipation dips much below their original
specification, the output power and sound quality declines. The
sound will begin to lose its definition, color and overall dynamic
drive. For the large power output tubes in Wright Audio's
single-ended integrated and power amplifiers, these qualities can occur
at about the 1500 hour mark and at about 2500 hours in our push-pull
amplifiers. It is very important to replace the tubes at these
points. You may think after 3 or 4 years of moderate use
that the amplifier sounds fine, but the degradation is so subtle and
over such a long period of time, that only new tube substitution will
remind you of the full sonic capabiilties of the equipment.
Besides the sound quality degradation, it is especially important that
you replace power tubes at this time to avoid a possible catastrophic
failure which may lead to an expensive amplifier repair. Never run
tubes past the expected lifetime waiting years until one fails
altogether in order to replace it. However, Wright Audio amplifiers are
built to endure some abuse through over-design with parts operating at a
fraction of their capability as well as having fuse protection.
Smaller tubes should be replaced at about the 2500 hour mark.
Besides the degradation in sound quality, small tubes can cause noise in the form of static, hum or hiss.
You should always keep a full set of replacement tubes on hand to make a
substitution in case a problem develops.
Never substitute a tube with a number different from what was originally
installed on your amplifier, or noted on the top, back or bottom of the
equipment. Contact Wright Audio if you have a
question regarding substitution of a tube number.
How To Change Tubes
Grasp the expired large power and rectifier tubes by the base, not the
glass. Pull straight out. Do not rock the tubes back and forth in an
effort to extract them. You may break off the guide post which will
remain in the socket and be impossible to remove without opening the
amplifier. Likewise, pull the smaller tubes straight out, as it is
possible to crack the glass at the bottom of the tube with excessive
rocking.
Wash your hands before inserting the new tubes. It is inevitable
that your hands will contact the glass. Vacuum tube bulb
temperatures for the power tubes can reach around 200 to 250 degrees
celsius or about 400 to almost 500 degrees Fahrenheit. If your hands are not clean, whatever has been
deposited onto the power output tubes during installation will cause
them to smell for awhile after they heat up!
To insert the new power and rectifier tubes, visually inspect the tube's
bottom post to orient the 'key' with the notch in the socket. This is
important because due to manufacturing tolerances of both the tube and
the socket, it is sometimes still possible to insert the tube with an
incorrect orientation which will damage the tube and likely the
amplifier once it is turned on.
Grasping the base, press the tube straight down into the socket.
Do not rock it excessively since again, the tube's center post can
break.
On the smaller tubes, a gap exists in the pins which serve for alignment
in their appropriate sockets.
Set the Tube Bias
Most Wright Audio amplifiers do not
require the user to make this electrical adjustment as it is done
automatically. For those amplifiers with a bias adjustment,
consult the manual with the amplifier for the procedure and setting.
New Tube Warranty
New tubes have a 90 day warranty
from receipt. |
