From jthornbur–(at)–arthlink.dot.net Sun Feb 14 23:01:16 CST 1999
Article: 342078 of alt.guitar
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From: jthornbur–(at)–arthlink.dot.net (Thorny)
Newsgroups: rec.music.makers.guitar,alt.guitar
Subject: INFO: How to “Pot” a pickup
Date: Sun, 14 Feb 1999 23:54:57 GMT
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Potting Pickups to Reduce Microphonic Feedback
How do I know if my pickups need potting?
Pickups will squeal and make a loud whistling noise similar to a
microphone when it feedsback. Some pickups are so
bad that if you touch them you hear a loud noise through the
amplifier. If you have a metal cover on the pickup, it could
make a loud “clank” when you touch it or start loudly humming.
This is not to be confused with the musical feedback that you get when
you crank your amp up and your notes sustain
indefinately – that is the good kind of feedback and this will not
effect that type of feedback. Potting pickups will actually
make it more likely that you can safely turn up loud enough to get
that type of feedback.
What is does potting do to my pickup anyway?
The term “potting” refers to the sealing of the coils in a solid
material. Potting serves two purposes, it reduces
microphonic feedback, and protects the inner coil from corrosion
(which can destroy your pickup). Potting in reference
to guitar pickups really is not just potting, but also “coil
emmersion.” Coil emmersion is allowing a solid (wax) to be
absorbed into the coil. We actually do both at the same time. Wax is
used because it works well, is inexpensive, and it
makes it possible to work on the pickup later. A correctly potted
pickup coil will have the wax absorbed throughout the
coil as well as the surrounding parts such as magnets, polepieces, and
metal covers. This eliminates movement of parts
inside the pickup – what makes a pickup microphonic.
What guitars/pickups are good candidates for this?
I have done this on humbuckers and single coils of many types. It
works on pickups with or without covers. If you are
going to have a metal cover on your pickup then pot it with the cover
on the pickup.
Any guitar with a microphonic pickup that is otherwise a good sounding
pickup is a good candidate for potting. Most
Seymour Duncan, later model Dimarzios, and premium model pickups a
already potted from the factory (including many
stock Gibson and Fender models also). If these pickups starting to
become excessively “microphonic” (this can happen)
then the procedure may need to be repeated. Recent Epiphone humbucker
pickups especially seem to benefit greatly
>from potting – their pickups sound pretty good except many suffer from
too much microphonic feedback. Since many of
the Korean imports are actually made by one company, it stands to
reason that the other Korean models likely have
similar noise problems. I have done this on many American, Japanese,
and Korean made guitars over the years. If it is
microphonic – it needs it.
What tools and supplies will I need?
Tools required to remove and re-install your pickup:
– 30 watt pencil tip soldering iron
– electronics grade solder
– screw driver (for removing pickguard or pickup rings)
Tools required to pot pickups:
– double boiler (can be home-made with a tin can in a pot of water)
– electric cook top preferred (wax is flamable – keep it away from
direct flames)
– candy thermometer (optional)
– pliers or tongs (to insert and remove the pickup in and out of the
melted wax)
– I use readily available canning wax
– Paper towels for cleanup
Are there any problems with this or is this dangerous?
Yes. Wax is highly flamable (remember candles are made of this
stuff). Do not attempt to do this without a double
boiler. It requires the same precautions as making candles. It is
not recommended to attempt to do this on a gas stove
because the flame may ignite the wax. Melted wax is obviously hot too
so don’t get burned.
There is always a small risk that you could damage a pickup. If you
have a particularly collectable instrument or it is of
questionable construction – don’t do it. That being said, I have done
very many of these over 15 years and never
damaged a single pickup.
What about removing the pickup covers?
It is not neccessary to remove the metal pickup cover from a
humbucker. It is easy to damaged pickups by trying to
take them apart – bad idea! Be careful if you choose to remove your
covers – remove at your own risk! If you have a
metal cover on your pickup – leave it on for the potting. Some
pickups (especially older inexpensive models from Japan
in the 70s) look like a regular Gibson humbucker but are not made to
have the covers removed. Most full-size
humbuckers made in the 90s can have their cover removed. Leave on any
tape that is directly over the coils. Trying to
remove it may damage your coils. If a pickup is already potted in a
hard plastic material (some older Ibanez models and
Select pickups come to mind) then you are out of luck – do not try to
remove a sealed plastic cover.
Strat pickups need their plastic white or black cover removed. Some
have tape around the coil, some do not. Leave the
tape on if it is there.
Why not replace the pickups with new potted ones?
Replacement pickups can cost $200 or more. That is why. I had a
newer model Epi and potted the pickups and an
astonishing thing happened – they actually sounded really good.
Potting your existing pickups costs very little and can
save you a lot if you like the sound of your existing pickups. Many
people are happy with one or more of their stock
pickups tone and may not want to change them. Most people would
rather have a stock guitar when they buy it used
too.
Instructions for potting a pickup
Make a sketch of your wiring before you remove your pickups so that
you can use it as a guideline to put your pickups
back in later. Mark the pickups (if needed) with a piece of tape on
the wire if you cannot easily tell from what position in
the guitar it was removed.
I make a double boiler out of a tin can (please clean the beans out
first) placed in a larger pan of boiling water. Again,
there are better tools out there than this, but they cost money. I
heat the wax in the can (in the pan of boiling water) until
it is only just hot enough that it completely melts (you can use a
candy thermometer to determine the minimum temp, but I
wing it). You will need to have enough wax melted to more than
completely submerge the pickup. If you heat it without
checking the temp, you run the risk of warping or melting your pickup.
Remove your pickups from the guitar and with a pair of pliers or
tongs, you lower it (in this case, with the metal cover
on) into the melted wax. Do not actually touch the coil windings with
the pliers or tongs as it may damage it. Grab the
pickup by the tab used to mount it. You leave it submerged and jiggle
it until all air bubbles seem to be out of it. This
takes a while (a few minutes) because the pickup has to heat up to the
temperature of the wax around it before it will
adequately penetrate the coils. Move the pickup every few minutes to
different angles to get the bubbles out and try to
avoid letting it stick to the side of the can.
Usually after 15-20 few minutes you jiggle it and the bubbles don’t
come out. Remove the pickup and allow to dry and
cool on a paper towel. Remember it is hot coming out of there. Let
it cool on the counter top. You may want to wipe
the face off a little while it is still warm because it is easier to
clean. Getting wax off after it has fully cooled is a pain.
Wipe off only the outside of a metal humbucking cover or the top of
the coil bobbins (where the pole pieces are at) and
not around the bottom or sides of the coil.
You may remove the can with the wax and keep it for the next time
(less clean up and waste that way). I have used it a
dozen or so times over the years. Clean the double boiler pan when it
is hot and it is easier if a little wax has dripped into
the water pan. Install it back into your guitar after you have let it
adequately cool using the wiring diagram you wrote
earlier.
You have now potted your pickups. Enjoy the benefits of less feedback
and noise.
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