So there you are with your multimeter in
hand, testing pickup coils from last month,
right? We discussed what an unusually
low resistance measurement would mean,
but it’s more likely that a faulty pickup will
give you an unusually high reading (e.g. infinite
resistance) than a low one. What does
this mean?
It probably means your pickup is now
composed of more than one piece of
wire, which is not a good thing at all.
Infinite resistance tells you that you have
no continuity between the meter leads
and that the path through which the current
must flow is probably broken. This
is referred to as an open circuit, which
means not complete.
I say the path is probably broken, and not
definitely broken, because sometimes cold
solder joints can cause a coil to appear to
be open when it’s really not. So if you read
infinite resistance on the meter, you may
just have cold solder joints. And if the solder
joints are exposed, as is the case with
Strat and Tele pickups, then simply heating
the two solder joints with a soldering iron
for a few seconds and allowing them to
cool may fix the pickup. This is always the
first thing to try when a pickup reads open,
and surprisingly, it often fixes the problem.
There’s another Strat/Tele pickup malady
that can also sometimes be fixed by
heating the solder joints: when the wires
along the pickup’s edge get scuffed during
installation into the guitar. Strat and Tele
(and many other) pickups have their coil
wire wrapped through eyelets and around
the edge of the pickup’s base several
times, before the leads are soldered on.
These wraps can be scraped along the
guitar body’s cavity wall when the pickup
is installed and some or all of the wraps
can break. In this case, heating the joint
will sometimes burn through the coil wire’s
insulation and restore continuity.
But let’s say that heating the solder joints
doesn’t work – you’ve tried that and the
pickup still reads open. What to do?
Presumably, the pickup didn’t ship from
the manufacturer this way, so someone
(you?) has damaged the coil, probably
by jabbing it with something sharp like a
screwdriver, or a pair of pliers, or something
similar. Coil wire is so thin that it can
easily break, so jabbing a coil with hard
metal objects is not a great way to engender
it with long life.
If the damage to the coil is in its outer
wraps, then the pickup is probably repairable.
The exception is if the coil wire is broken
at the ground connection, as shown in
the following illustration.
If this is the case, then the pickup needs
to be rewound or replaced. There’s no practical
way to connect the two broken ends
of the wire together.
On the other hand, if the wire is broken at
the hot connection (the white wire), or if
it has sustained some damage to the outside
of the coil, then it’s probably repairable
by peeling it. This can often be successfully
done in 15 or 20 minutes, and I’ll tell
you all about how to do it next month.
Until then!
George Ellison
Founder, Acme Guitar Works
acmeguitarworks.com
george@acmeguitarworks.com
302-836-5301