POTENTIOMETER RESTORATION BY JOHN BROWN
Agorgeous ’ 54 Gibson Les -Paul came through our shop
for show-and-tell one day. I must
admit it was an exquisite-looking,
mint-condition guitar, and if it
weren’t for the one volume pot
that had been replaced, it would
still be in 100-percent original
condition. There are people who
wouldn’t have a big issue with
this, yet others would react to the
replaced pot and think, “If the
volume pot has been changed,
what else is not straight on the
guitar?” This is just one of those
concerns and quirks of doing biz
in the world of vintage guitars.
Many very qualified and
well-educated collectors and
dealers say that in today’s vintage guitar market, you have to
accept that things get changed
along the way when it comes to
worn-out electronic parts. It is
just a reality, like a Stradivarius
violin needing a neck rebuild,
fingerboard level, or top or back
removal over time.
That’s all true, but when
it comes to manufacturing
potentiometers, most of today’s
materials are subpar compared to
the virtually unbreakable materi-
als of yesteryear. This is certainly
true when it comes to guitar elec-
tronics. Have you ever noticed
how often you might replace the
pots on your main guitar from
the ’70s or ’80s, or how your
newer guitar can lie in its case
for a few months and when you
go to play it, the volume pots are
scratchy and won’t even clean up
with proper cleaner?
of manufacture (you’ll need
a source-date code system to
interpret them).
Consider this: In pursuing
ultimate tone, if we’re really
stuck on the accuracy of a 500
kΩ pot, we have to be aware
of some serious variability
going on here. The IRC pot
I was restoring reads 550, yet
I can buy a bag of modern
pots and most of those will
read under 500 kΩ, at times
even as low as 450 kΩ. That’s
a potential 100 kΩ difference
between the two. Wow—isn’t
that an eye-opener? It’s a good
idea to always use a meter and
select your pots accordingly.
My next step was to use an
angle vise (which works well
because it has some girth)
to hold the pot as I tried to
manipulate its shaft (Photo
2). Unfortunately, the pot’s
durable brass shaft wouldn’t
budge loose—it was as if it was
once glued into position. This
meant it was time to investigate inside.
Notice how I attached two
maple strips to the vise jaws
to support the pot and protect
it from scratches or damage. I
used a mini screwdriver that’s
slightly narrower than the chassis-support tabs to bend them
open. The size is important,
because later when everything
is reassembled, any micro pressure marks will be hidden under
those four tabs. This creates an
invisible restoration.
We’ll conclude our pot-resto-ration project next month and
list the tools you need for this
work, so be sure to swing by for
the second installment.
Photo 1: Measuring the potentiometer’s resistance with a digital multimeter.
Photo 2: Carefully prying open the pot’s chassis-support tabs.
JOHN BROWN is the
inventor of the Fretted/
Less bass. He owns and
operates Brown’s Guitar
Factory, a guitar manufac-
turing, repair, and restoration
facility staffed by a team of
talented luthiers. His guitar-tool and acces-
sory designs are used by builders all over the
world. Visit brownsguitarfactory.com or email
John at info@brownsguitarfactory.com.
