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The Electromuse Eye-Beam: My Very First Pickup Rebuild
by Ralphie B., age 55-1/2
Introduction
This pickup was installed in an unbadged lap steel, ca 1940s-1950s. Depending on your attitude, it may be either the crudest or the most elegant design possible- a chunk of magnet wrapped in wire.
The pickup looks like a double-rail humbucker- but it isn't. The magnet is alnico, cast into an I-Beam shape about 1" wide; its jagged ends infer the piece was snapped from a longer bar. The i-beam is magnetized "across the bar" (one flange is North, the other South) and the coil is wound "along the bar", between the flanges. (I believe some would call this orientation "wrong", with most of the magnetic flux travelling parallel to the strings.)
The guitar appears to share all electronics and hardware with the Electromuse "canoe paddle"- the only difference being body wood, shape, and finish (pine with straight sides and hallucinogenic blue paint job vs. mahogany paddle with natural finish).
Original Construction
Unfortunately, I neglected to take "before" photos of the pickup and lap steel.
However, some discussion and description can be found here http://music-electronics-forum.com/t25965/
and this site has photos of an Electromuse "canoe paddle" autopsy Electromuse1p8
Condition as Found
The pickup appears to have been "potted" in beer, and the magnet had rusted severely, breaking inner coil wraps. As originally assembled, I can't see how the pickup could produce a healthy signal. The magnet was loosely wound with a fairly small cluster of gossamer wire, centered between the flanges to resemble some kind of cocoon.
Rebuild Philosophy
I'm not sure if this project should properly be called a rebuild, a refurb, or a rehab. Rather than restoring the piece to original condition, my goal was to assemble a reasonably robust, quiet (noise-wise) pickup with output compatible with modern amplifiers, using on-hand and readily obtainable materials. I also sought to retain as many of the original electronic components as possible (21K volume and 140K tone Allen-Bradley potentiometers; tone capacitor- labeled .05uF but reads .075uF).
Some Differences from Original Design
1) Insulation
The Eye-Beam used heavy 2" wide cloth tape to insulate the coil from the bare, jagged-edged magnet and to cover the coil.
Using a rotary tool, I ground the magnet ends smooth. Since the pickup was killed by rust, I thought it prudent to spray the magnet with Rustoleum appliance enamel. Wanting maximum possible space available for the coil, I used a combination of clear plastic tapes for electrical insulation and thin 1" wide cloth "drugstore tape" for for coil wire padding and protection.
2) Grounding, Shielding, Lead Wires
The magnet was not originally grounded, nor the coil shielded. I grounded the magnet and shielded the pickup with copper foil. I also foil-shielded the control cavity.
The Eye-Beam originally used a bare lead wire for Start/Ground and a blue lead wire for Finish/Signal. I used a bare lead for magnet/shield ground, white lead for Start/Signal+, and black lead for Finish/Signal-.
3) Strain Relief
As originally built, the Start lead wire was spliced to the coil wire at the middle of one end of the magnet; the coil was then loosely wound over the splice. The Finish lead was soldered to the coil wire with no strain relief. I thought this configuration seemed prone to breakage, and sought to anchor the leads in a less vulnerable fashion.
4) Coil Wire Gauge and Turns
As found, this Eye-Beam was wound with few turns of thin wire. I aimed to wind within the range 2300-3200 turns of 38 AWG, for a DCR of 600-822 ohms. If anyone is interested, I'll post an explanation of the calculations and hunches that led to this decision.
5) "Super-Charging"
Expecting a fairly weak output from this pickup, I planned on experimenting with hanging small neodymium magnets onto the alnico magnet's flanges to increase output. As it turned out, the pickup's output was more than strong enough for my needs.
6) Circuit Wiring
I replaced the ratty "once white" 12-1/2 ft pigtail-to-plug with a 1/4" phone jack. This was a difficult decision, because: a) I had to chisel petrified pine to fit the jack; and b) I thought a new pigtail in blue plaid braid would look too kewel. However, practicality (almost) won out. Thinking the pickup's impedance might be low enough to directly drive a mixer's balanced line-in (typically ~10Kohm input), I used a TRS jack wired T=Sig+, R=Sig-, S=Shield. When a standard "mono" instrument cable is plugged in, R is shunted to S and it ends up being "normal" wiring.
-----------------------------
THE REBUILD STORY, as told in pictures, to follow.
-rb
by Ralphie B., age 55-1/2
Introduction
This pickup was installed in an unbadged lap steel, ca 1940s-1950s. Depending on your attitude, it may be either the crudest or the most elegant design possible- a chunk of magnet wrapped in wire.
The pickup looks like a double-rail humbucker- but it isn't. The magnet is alnico, cast into an I-Beam shape about 1" wide; its jagged ends infer the piece was snapped from a longer bar. The i-beam is magnetized "across the bar" (one flange is North, the other South) and the coil is wound "along the bar", between the flanges. (I believe some would call this orientation "wrong", with most of the magnetic flux travelling parallel to the strings.)
The guitar appears to share all electronics and hardware with the Electromuse "canoe paddle"- the only difference being body wood, shape, and finish (pine with straight sides and hallucinogenic blue paint job vs. mahogany paddle with natural finish).
Original Construction
Unfortunately, I neglected to take "before" photos of the pickup and lap steel.
However, some discussion and description can be found here http://music-electronics-forum.com/t25965/
and this site has photos of an Electromuse "canoe paddle" autopsy Electromuse1p8
Condition as Found
The pickup appears to have been "potted" in beer, and the magnet had rusted severely, breaking inner coil wraps. As originally assembled, I can't see how the pickup could produce a healthy signal. The magnet was loosely wound with a fairly small cluster of gossamer wire, centered between the flanges to resemble some kind of cocoon.
Rebuild Philosophy
I'm not sure if this project should properly be called a rebuild, a refurb, or a rehab. Rather than restoring the piece to original condition, my goal was to assemble a reasonably robust, quiet (noise-wise) pickup with output compatible with modern amplifiers, using on-hand and readily obtainable materials. I also sought to retain as many of the original electronic components as possible (21K volume and 140K tone Allen-Bradley potentiometers; tone capacitor- labeled .05uF but reads .075uF).
Some Differences from Original Design
1) Insulation
The Eye-Beam used heavy 2" wide cloth tape to insulate the coil from the bare, jagged-edged magnet and to cover the coil.
Using a rotary tool, I ground the magnet ends smooth. Since the pickup was killed by rust, I thought it prudent to spray the magnet with Rustoleum appliance enamel. Wanting maximum possible space available for the coil, I used a combination of clear plastic tapes for electrical insulation and thin 1" wide cloth "drugstore tape" for for coil wire padding and protection.
2) Grounding, Shielding, Lead Wires
The magnet was not originally grounded, nor the coil shielded. I grounded the magnet and shielded the pickup with copper foil. I also foil-shielded the control cavity.
The Eye-Beam originally used a bare lead wire for Start/Ground and a blue lead wire for Finish/Signal. I used a bare lead for magnet/shield ground, white lead for Start/Signal+, and black lead for Finish/Signal-.
3) Strain Relief
As originally built, the Start lead wire was spliced to the coil wire at the middle of one end of the magnet; the coil was then loosely wound over the splice. The Finish lead was soldered to the coil wire with no strain relief. I thought this configuration seemed prone to breakage, and sought to anchor the leads in a less vulnerable fashion.
4) Coil Wire Gauge and Turns
As found, this Eye-Beam was wound with few turns of thin wire. I aimed to wind within the range 2300-3200 turns of 38 AWG, for a DCR of 600-822 ohms. If anyone is interested, I'll post an explanation of the calculations and hunches that led to this decision.
5) "Super-Charging"
Expecting a fairly weak output from this pickup, I planned on experimenting with hanging small neodymium magnets onto the alnico magnet's flanges to increase output. As it turned out, the pickup's output was more than strong enough for my needs.
6) Circuit Wiring
I replaced the ratty "once white" 12-1/2 ft pigtail-to-plug with a 1/4" phone jack. This was a difficult decision, because: a) I had to chisel petrified pine to fit the jack; and b) I thought a new pigtail in blue plaid braid would look too kewel. However, practicality (almost) won out. Thinking the pickup's impedance might be low enough to directly drive a mixer's balanced line-in (typically ~10Kohm input), I used a TRS jack wired T=Sig+, R=Sig-, S=Shield. When a standard "mono" instrument cable is plugged in, R is shunted to S and it ends up being "normal" wiring.
-----------------------------
THE REBUILD STORY, as told in pictures, to follow.
-rb
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