To remedy [sound
cutting in and out],
spray electronic con-
tact cleaner—only
this time use the
type that does have
lubricant—into each
[effects loop] jack,
and then insert and
remove a cable 8
to 10 times.
electronic contact cleaner, and then insert
and remove each tube in the socket 8 to 10
times. (Note: Be sure your electronic contact cleaner is the type without lubricant—
lubricant can attract dust and debris, which
can become conductive.) Once you’ve
cleaned all the sockets, leave all of the tubes
out for 5 to 10 minutes so that the cleaner
can evaporate. After the sockets are dry,
replace the tubes and try the amp again. If
the symptom has cleared up, you’ve taken
care of the issue. If not, try the socket-cleaning procedure again—sometimes it
can take more than one cleaning to get the
job done. If the problem still persists after
a couple of cleanings, the sockets may need
to be re-tensioned or replaced, which is
probably best left to a professional.
If your amp isn’t making any sound, it may have a bad speaker connection. You can
test whether the speaker is getting a proper signal by connecting one multimeter lead
to the sleeve (as shown with the black lead above) and the other to the tip.
Does sound from the amp cut
in and out while you play?
This can be due to quite a few things,
one of which can be related to the tube
sockets (see the previous section on
cleaning tube sockets).
If your amp has an effects loop, the
problem could also be that the contacts in
its 1/4" jacks are dirty or oxidized—espe-
cially if you don’t use the loop. To remedy
this, spray electronic contact cleaner—only
this time use the type that does have lubri-
cant—into each jack, and then insert and
remove a cable 8 to 10 times. Afterward,
leave the plugs inserted for 15–30 min-
utes—or even overnight, if possible. This
will leave the jacks’ switching contacts open
and give the cleaner a chance to dry. You
can then remove the cable and try the amp
again. (Note: As a preventive measure, it’s
not a bad idea to perform this type of jack
cleaning on your input and speaker jacks.)
Does the amp not make
sound at all?
This can be due to an open speaker con-
nection. To check for this, unplug the
speaker cable from the head (leaving the
other end connected to the cab), and use
your multimeter to measure the resistance
of the speaker load. Set the meter
to read resistance in ohms, connect
one lead of the meter to the body (sleeve)
of the plug, and then connect the other to
the tip. A typical 16 Ω load will measure
approximately 12–14 ohms, an 8 Ω load
will measure approximately 6–7 Ω, and a 4
Ω load will measure approximately 3 Ω DC
resistance with the meter. If you can’t get
a resistance measurement, try again with a
spare speaker cable. (Note: For testing pur-
poses, a 1/4" instrument cable can be used,
but you should not use one as a permanent
substitute for a proper speaker cable.)
