use an oven mitt or ‘Ove’ Glove. This same
technique can be used to find an offending
output tube.
If tapping on the amp with all the volume
controls set to minimum produces no noise, set all
the volume controls to your typical settings and
try again. If the noise in question is now present,
go through the preamp-tube tap test once again,
starting with the tubes closest to the input(s) of the
amp—you’ve most likely narrowed it down to the
first couple of gain stages.
Before removing tubes to clean their
sockets, label the tubes and their sockets to ensure you replace them in the
spots that were producing satisfactory
results prior to the static problem.
If none of the above troubleshooting
techniques produce the noise in question and your amp has a mechanical
type reverb (i.e., a spring unit), turn up
the reverb control. If the noise is now
present, the reverb drive and/or recovery tube could be the cause. Unless you
know the specific location of these tubes,
you may need to go through the tap test
one more time to find exactly which tube
is at fault. (If your amp is a blackface
or silverface Fender style, looking at the
amp from the rear, the reverb-driver tube
is generally a 12AT7 and it’s usually third
from the right, while the 12AX7 reverb
recovery tube is fourth from the right,
just past the small transformer.)
Is the amp making crackling
or popping noises when you’re
not playing?
If so, this is can be caused by faulty
preamp or power tubes. The best course
of action here is pure substitution. One
by one, replace each preamp tube and
see if it alleviates the noise. If none of
the preamp tubes seem to be the cause,
try replacing the full set of output tubes
with your set of matched spares. If no
tube substitution alleviates the problem,
the amp will need to be serviced, because
there’s a good chance it has a failing plate
or cathode resistor in the preamp.
Is the amp making loud, stat-ic-like noises when you play?
This could be due to dirty, oxidized, or
compromised connections in the tube
sockets. To find out, while the amp is in
