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This poor old bass found its way to our house a few years ago
looking for fresh strings, a setup, and some TLC. It's a 1999 SB-2
that's been in the hands of high-schoolers. It has a few rough spots,
but it's a sound player.
I decided to turn this into a small project. |
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Here's what the original electronics looked like. This is
G&L standard. |
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This image shows the shielded pickup cavities and the channel that
runs from the neck cavity to the control cavity. There's lots of room
around the neck pickup because it has the pickguard. However, clearance
around the bridge pickup is tight. The sides aren't too bad, but the
ends are very close. I shielded the bottom and long sides of the cavity
and ended up with a movable pickup. If you look carefully, you'll note
that there is a small piece of foil covering the hole to the control cavity.
More on that in a below. |
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Those nice neat holes in the foil for the springs were made with
this and a small hammer. A couple medium-sized blows to the punch and the
foil was scored enough to easily lift out. The body was well supported
for this process. |
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Additional shielding on the pickguard. Shielding the entire
back of the guard is overkill. The pickup cavities and lead channels
were covered. |
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This image shows a wire soldered to the bottom of the control cavity.
This wire, when connected to the star ground lug shown and described
below, ties all the foil on the bass to ground. |
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The completed control circuit - sorta. The bundle of green wires
is comprised of all the various ground connections from the entire instrument
soldered to a 3/8" ring terminal, which is clamped in place under the neck
pickup control. This is the star ground I mentioned above.
Care should be taken when orienting the jack so that it
doesn't short to the foil on the side of the control cavity.
I said that the circuit was "sorta" complete because this image shows
the pots wired backward. The red and green pot leads should be swapped. This
was corrected before the bass was buttoned up. |
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Under the heading, "It's All In The Details", I also shield the
hole that runs between the bridge pickup cavity and the control cavity. You
can see one end of this shield here. Note that this shield will tend
to slightly darken the sound of the pickup whose leads go through it. This
would be the case if the wires themselves were shielded. |
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The shield tube is made using a piece of RG59-U coaxial cable -
TV cable. It has to be the good stuff with copper braid shielding.
I strip the braid out of the jacketing to get the tube. What
you see below are, left to right, the piece of coax, the empty outer jacket,
the inner conductor with dilectric, and an empty copper braid tube. |
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I narrow one end and tin it to hold it together, then feed it through
the hole in the body. I then spread the other end into a bell shape
and solder it to a cavity wall. I cut the excess off the now free end,
leaving about 1/4" protruding into the cavity. I spread it into a bell
shape and solder it to the other cavity wall. This is where that little piece
of foil in the bridge pickup cavity gets used - as a solder point. Care
must be taken in the bridge pickup cavity to keep the end pushed as tightly
as possible to the wall when soldering to avoid interfering with the pickup
cover. Push the wires through as seen above and install the pickup. |