Last month we began discussing what to
do with coils that have tested open with
a multimeter. As mentioned last month,
when the coil wire is broken at the ground
connection, there’s not much that can be
done short of a rewind.
However, there are two other conditions
that can cause a coil to read open on
a multimeter, but have easily repairable
damage. The first is when the coil wire is
broken at the hot connection and the second occurs when there is a break in one of
the outer coil windings. Both problems are
shown in the illustration below.
BROKEN WIRE AT HOT CONNECTION
BROKEN OUTER COIL WINDING
The fix for both pickups is to peel their
coils. Peeling means removing sufficient
wraps of wire from the coil to get past
the break. Then the “good” end of the
remaining coil wire is connected to the
hot lead. In the first example, where the
coil lead is broken at the hot lead, you’ll
only be removing a wrap or two, so fixing
this problem will have no effect tonally.
In the second example you may be peeling a bunch of wire off of the coil, which
may result in a very slight decrease in
output. Despite the fact that it may seem
like you’ve removed a ton of wire, in most
cases the actual percentage of wraps that
are removed is negligible, so the change in
output should be hardly noticeable, if at all.
The first thing to do is to heat the solder
joint that connects the white wire to the
pickup’s base and remove the white wire
– you’ll also need to remove any coil wire
that is still wrapped through the eyelet.
Take your time and be careful while heating
the eyelet with a soldering iron, picking any
remaining wire strands out with needle-nose pliers or tweezers. This process may
also remove any remaining solder that fills
the eyelet, but if it doesn’t you’ll need to
remove the remaining solder with a solder
sucker or desoldering braid.
One word of caution: be careful if you’re
working on a pickup with a molded plastic
bobbin, since heating the metal eyelet
could cause the surrounding plastic to
melt. If this is the case, use just enough
heat to allow you to remove the coil wire
and any remaining solder from the eyelet.
You should now have something that looks
COIL WIRE LOOSE END
The next step is to peel off some of the
layers of wire; the amount to be removed
will depend on where the coil is broken.
If it was broken right at the point where
it attached to the eyelet, as in the first
example, then you’ve already removed the
broken section and peeling one or two
wraps will suffice. Simply remove a wrap
or two, then re-attach the wire to the eyelet, re-insert the white lead and solder it
into place. Be sure to thread the coil wire
through the eyelet several times, and make
sure it’s taut before you solder it.
You should also remove the insulation from
this section of the coil wire first in order to
get a solid connection. I’ve seen instances
where the soldering iron plus the molten
solder/flux will heat the wire sufficiently
to burn through the insulation and create
a good connection, eliminating the need
to remove the insulation manually, but it’s
better to be safe than sorry. It’s definitely
easier to remove the insulation now rather
than having to do it later. The insulation can
be easily removed by pulling the wire’s end
between your thumb and a piece of 600-
grit sandpaper a couple of times. You’ll see
a subtle change in color where the insulation is removed, so you’ll have a visual
indicator that you’ve stripped the insulation. You can also put one of your meter
leads on this section, and the other on the
pickup’s black lead, and test for continuity. If you break the wire in the process of
removing the insulation, then simply peel
off another wrap and try again.
Assuming that the break is further along,
on one of the outer coil windings, then
you’ll peel the wire until you reach the
break. Now there are a couple of new considerations that we’ll discuss in detail next
month. Until then!
Founder, Acme Guitar Works