art's theremin page_ the 145 theremin

3/9/2014 Art's Theremin Page: The 145 Theremin

http://www.theremin.us/145/145.html 1/11

The 145 ThereminA New Version of the Model 144 Theremin

Published November 19, 2000Updated March 31, 2011

Contents

Legal NoticeSafety Notices

AcknowledgementsIntroductionAssembly

SchematicsDrawings

Parts TableTest and Calibration Procedure

Photos

Legal Notice(back to contents)

The information contained in this document is ©2000, 2001, 2002, 2004, 2005, 2009 by Arthur Harrison. Any reproduction of the information contained in thisdocument, electronic or mechanical, shall only be used with Arthur Harrison's permission, and shall acknowledge him as the copyright holder and author.

Use of the information contained in this document for personal or commercial financial gain, such as the manufacture and sale of electronic musical instruments orparts thereof, is prohibited. Unless specifically stated in a written contract, Arthur Harrison grants no licence for the commercial exploitation of the concepts anddesigns embodied in this document. Refer licensing inquiries to: [email protected].

The information contained in this document may only be reproduced in small quantities when the purpose for its use is the dissemination of information to studentsor hobbyists, and may not be distributed in any form, electronic or mechanical, for the purposes of any party engaged, directly or indirectly, in commercialenterprises.

Arthur Harrison assumes no liability for any damages, direct, or consequential, which may arise from the dissemination, application, or misapplication of the contentcontained in this site. The User of the information provided in this site assumes all responsibility for any damages, direct or consequential, which may arise from itsuse. Arthur Harrison retains the right to alter the content within this site at any time without notice.

Safety Notices(back to contents)

DANGER: Do not play this instrument at a high volume, especially when using headphones. Use headphones that have a built-in volume control, andadjust the volume control for a comfortable level. Hearing experts advise against the continuous, extended use of headphones.

DANGER: Some of the components used in this construction are "polarized," which means that they will only function properly when inserted into thecircuit in the right direction. Always observe component polarities carefully, and double-check the orientation of transistors, diodes, integrated circuits andpolarized capacitors before applying power to any circuit. Do not reuse a part which has been subjected to improper insertion.

DANGER: Wear safety glasses and use all appropriate safety equipment when working with tools and materials. Always follow safe shop practices andobey safety rules.

Acknowledgements(back to contents)

The author thanks Konley Aschenbach, whose assistance in the layout design and construction of the 145 theremin prototype is greatly appreciated.

Introduction(back to contents)

Since the publication of the type 144 theremin project article in September, 1998, many of them have been successfully constructed. As in the 144, and itsforerunner, the Southwest Technical Products model 142, the 145 theremin retains a heterodyne topology similar to that used by Mr. Theremin in his originalinstruments.

The 145 theremin is similar to the 144 in most respects, excepting the types of oscillators used. The 145 theremin oscillators are differential-pair types, incomparison to the Colpitts types in the 144. The approximate operating frequencies for the 145 theremin are 270kHz for the volume circuit and 360kHz for the pitchcircuit. Compared to the 144, the 145 has improved pitch-arc linearity, with A440 occurring at about 10 inches of hand distance, compared to about 5 inches for the144. The practical pitch range for the 145 is about 4 1/2 octaves.



Inexpensive silicon rectifiers are used as varactors to provide a volume oscillator tuning range of about 1200Hz and a pitch reference oscillator tuning range of about700Hz. These frequencies will typically vary within ±10 per-cent among instruments, due to tolerances.

In the new design, oscillator outputs are taken from the resonant L-C pairs, and are low-distortion sine waves. Weak coupling is provided between the two pitchoscillators via C8 and R10 to induce a "lock" condition for zero-beat when the pitch hand is absent. The pitch oscillator levels at the mixer input are unequal, and themixer output amplitude is significantly reduced in comparison to the 144. This reduction provides a more consistent timbre for varying volume levels, since theamplitude-modulating FET, Q13, is operated in a more linear region. As a result, the 145's timbre has less harmonic content than the 144's. An added filter pole atthe mixer's output, R17-C13, provides improved reduction of RF products at the audio output. The audio amplifier has an added AC gain network, R47-C39, in theemitter of the Q14 preamplifier transistor.

As in the 144 theremin, the 145 features the convenience of low current consumption (less than 20 milliamperes) from a single 9-volt battery, enhancing portabilityas well as safety in construction and use.

The following graph illustrates the approximate relationship of pitch and hand distance for a 145 theremin, when constructed and calibrated as specified in thisarticle:

The volume range for the instrument is approximately 0 to 700mV peak-to-peak for a volume hand distance variation of 12 inches. The noise amplitude is constantat approximately 2.5mV peak-to-peak, giving a overall signal-to-noise performance of about 49dB.

I do not recommend this theremin project for the novice, since it exhibits many sensitivities that are greatly affected by the physical placement of components, aswell as requirements for test equipment not normally obtainable by the casual experimenter. For those confident in their abilities, assembly drawings have beenfurnished as a guide for construction. Adherence to the perscribed lay-out is strongly advised.

Assembly(back to contents)

A comprehensive set of mechanical drawings is provided for the 145 theremin. These drawings represent a straightforward implementation of the instrument,constructed on a 17" by 11" plywood base, without an enclosure. This construction method is especially suited for educational demonstrations, since the circuitry isexposed for viewing. Alternatively, the user may enclose the circuit board in a suitable cabinet. If you enclose the theremin, minimize capacitance between thecabinet, antennas, and antenna connections. Refer to the assembly drawing to view an overall lay-out of the instrument. Refer to the mounting base drawing forspecific locations of the antennas, brackets, circuit board, and battery holder.

As shown in DETAIL B of the assembly drawing, the circuit board is supported on eight threaded metal standoffs. A metal ground plate is mounted under the circuitboard. The plate has eight holes that align with the circuit board's mounting holes. To ensure proper alignment of the plate with the circuit board, it is recommendedthat the circuit board be used as a template to locate the holes in the plate. This is best done with the circuit board blank, prior to its assembly, so that it can lie flatagainst the plate. It is also recommended that the blank circuit board be used as a template for hole locations in the wood base. Note that the holes in the plate are alittle larger than required for the number 4-40 machine screws used. This provides allowance for tolerances.

A clear plastic cover is installed above the circuit board. This is recommended to prevent damage to the circuit during transport and demonstration. Again, it isconvenient to use the blank circuit board as a template to locate the holes in the cover. The cover is attached to the circuit board with eight male/female-threadedstandoffs, screws, and nylon washers, as illustrated in the assembly drawing. Two holes in the cover permit access to the trimming capacitors for calibration.

As noted in the assembly drawing, the upper eight male/female threaded standoffs that support the plastic cover screw into the eight lower standoffs that support thecircuit board. Apply a thin coating of light oil (any cooking oil will work fine) on the male threads of the upper standoffs before screwing them into the lowerstandoffs. This will prevent the threads from jamming, which may otherwise occur when aluminum parts are threaded together.

A 5/8"-27 internal-thread fixture may be attached to the underside of the base so that the instrument can be mounted on a microphone stand. The Atlas Sound typeAD-11B is suitable for this purpose. (Atlas Sound, 1859 Intertech Drive, Fenton, Missouri 63026 USA, 1-800-876-7337.)

The potentiometers, power switch, and headphone jack are mounted on the control mounting bracket at the front of the base. The line output jack is mounted on thejack mounting bracket at the rear of the base. The battery is secured to the base with a Keystone type 71 spring-metal clip. The clip may be mounted directly to thebase with two #2 self-tapping screws, however, the screw heads will prevent the battery from seating completely. An alternative, preferred solution is to solder theclip to a saddle plate with mounting holes outside the battery's footprint, as illustrated in the battery holder drawing. The soldered connections to the potentiometersand the power switch are covered with 1/2"-lengths of heat-shrinkable tubing that provide stress relief for the connections, as well as preventing the potentiometer'sflexible terminals from touching each other.

The volume and pitch antennas extend from the left and right edges of the base, respectively. As indicated in DETAIL A of the assembly drawing, the antennas areelectrically insulated form the base with 1/2" threaded nylon standoffs. The nylon standoffs are used to separate the antennas from the base, thus reducing straycapacitance. The antennas are connected to their respective circuit board terminals with 16 gauge solid bus wire. Wire attachment is made with a number 6 solderlug, secured by one of the mounting screws at each antenna.

Frequently, users inquire if the plate antennas used for these theremins may be substituted with the traditional form of theremin antennas; the monopole for pitch andloop for volume. Although this may be done, the results will be marginal, since these antenna topologies present less capacitive coupling to the hands, and thus areless efficient. As a result, the theremin's response will occur within smaller arcs of hand movement, closer to the antennas.

Circuit Board

Refer to the circuit board assembly drawing, circuit board component locations drawing, and the circuit board symbol key for component placement and wiring.



The circuit board components are mounted on a sheet of material commonly called "perfboard." The perfboard in the parts list, Vector type 169P84WE, is made of asturdy glass-epoxy material which resists cracking. Phenolic and paper-epoxy type boards are not recommended, because they are more fragile. The perfboard isfurnished with a matrix of 0.042" diameter holes on 0.1" centers. The item listed has 169 columns by 84 rows of holes, and is cut to a size that has 57 by 75 holes,which is 5.8 inches by 7.6 inches.

The board can be cut by deeply scoring along a row of holes with an awl, and then breaking it along the score. If you use this technique, clamp the board and astraight-edge guide securely to a sturdy work surface. Once the board is cut to the proper size, use the circuit board assembly drawing to locate and drill the eight0.140"-diameter mounting holes.

The Vector T68A terminals are pushed into the top side of the perfboard, inserted with long-nosed pliers. They can be quite hard to push in. If so, use a slightalternating clockwise-counterclockwise twisting motion while you push. Make certain that each terminal is securely and squarely seated. The top of the T68Aterminal is a two-tined fork, and accepts one or more component leads, or wires that extend from the periphery of the board. The connections to the fork end of theterminal are soldered. The other end is a square cross-section pin, designed to accept a "Wire-Wrap®" connection. The application of the T68A terminal is illustratedbelow. FIGURE A shows the side view of two terminals with a typical axial-leaded component, such as a resistor, soldered in place. FIGURE B is the front view ofa terminal with two levels of wrapped wire. Either one or two levels of wire can be accommodated on each terminal.

Wire-Wrap® is a technique for making rapid, solderless connections. Here are simplified instructions for using a Wire-Wrap® tool. If you do not have Wire-Wrap®tools, the bottom-side connections may be soldered, instead. Before you solder to the pin ends of the terminals, first cut them to a length of 1/4". This will providespace for pliers and the soldering iron tip. The solid conductor, tinned, 26 gauge Kynar® insulated wire specified in the parts list may be either wrapped or soldered.Tefzel® or Teflon® insulated wire may also be used. These insulations are less likely to melt from normal soldering temperatures, but they are harder to strip thanKynar®. A wire with a tinned conductor is desirable, because it solders much more easily than bare copper, which tends to oxidize quickly.

The Vector T68A terminals are quite costly. They are only sold in packages of 1000 for $91.86. Unless the builder routinely requires these terminals for severalprojects, this will probably be considered an unreasonable expense. To reduce cost, the Vector type T68 terminal, which has a longer tail than the "A" version, maybe used. The T68 is less expensive at $49.17 per thousand, and they are also available in packages of 100 for $8.35. If you use the longer, T68 terminal, then thelength of the eight threaded metal standoffs used to mount the circuit board should be increased from 5/8" to 3/4" so that the terminals do not touch the ground plane.Note that 250 terminals are required for this project.

A wide braid material, normally used for desoldering, is used for the circuit board's top-side ground "bus." This thick conductor minimizes voltage differences fromone ground point to the other. Note that the braid is placed against the edge of the terminals without wrapping or crimping. Make sure that the braid is pusheddirectly up against the terminal, and inspect each connection carefully to ensure that it is securely bonded after soldering.

22 gauge, stranded, insulated wire is used to interconnect the circuit board, controls, jacks, and battery. All the connections are made to the periphery of the board atthe terminals designated "1" through "16" in the circuit board assembly drawing. To avoid stray capacitance, route these wires in a direct fashion, keeping them awayfrom the antennas, antenna wires, and the area beneath the circuit board.

DANGER: It is imperative to observe the correct orientation of the following types of components:

Transistors:

The circuit board assembly drawing distinguishes transistor orientation (flat up or down) with different symbols. Refer to the transistor lead identification drawingfor further clarification.

Electrolytic capacitors:

Observe the polarity marking on the electrolytic capacitors and be sure they comply with the circuit board assembly drawing. Polarity indication varies amongmanufacturers, and even among one manufacturer's lots. Examine each polarized capacitor carefully to determine the correct orientation. DANGER: Anincorrectly-inserted electrolytic capacitor can become extremely hot and explode, causing injury, even though the circuit power is limited to the output of asmall 9-volt battery!

Diode and rectifiers:

The rectifiers and diode have one end marked with a band, corresponding to the banded ends in the circuit board assembly drawing. The band denotes the "cathode"lead, and corresponds to the bar part of the schematic symbol. The end without a band designates the "anode," which corresponds to the triangular part of theschematic symbol, as shown in the drawing below.

The version of the 1N4001 rectifier specified has an opaque, black plastic case. Versions of the 1N4001 that have a clear glass case should not be used insubstitution, because such rectifiers exhibit changes in capacitance with variations in light.



Integrated Circuit:

Determine the location of pin 1 on IC U1's package, and insert it in the socket accordingly.

Schematics for 145 Theremin(back to contents)

The 145 theremin schematic is presented below in six sections. A single-image schematic can be viewed via the following link: One-page Schematic

The calibration procedure for capacitor selection, referenced in the Variable Oscillator and Volume Processor drawings, can be viewed via the following link: Testand Calibration Procedure



Drawings for 145 Theremin(back to contents)

One-page Schematic

AssemblyCircuit Board Assembly

Circuit Board Component LocationsCircuit Board Symbol Key

Transistor Lead IdentificationMounting Base

AntennasGround Plate

Control Mounting BracketJack Mounting Bracket

Battery HolderPlastic Cover

Parts Table(back to contents)

Note: The four inductors required for this circuit, J.W. Miller type 4652, are now available from Harrison Instruments. Please contact Harrison Instruments forordering information.

DISTRIBUTOR LINKSMouser Electronics http://www.mouser.com/

Harrison Instruments http://harrisoninstruments.com/Parts/parts.htmlMcMaster-Carr http://www.mcmaster.com/

ITEM DESCRIPTION VALUE MANUFACTURERMANUFACTURERPARTNUMBER

SUPPLIERSUPPLIERSTOCKNUMBER

QTY

A1,A2(NOTE 1) ANTENNA . . . . . 2

B1 BATTERY 9 VOLT,NEDA 1604 EVEREADY 522 MOUSER 525-522 1

C1,C2,C18,C30,C31

TANTALUMCAPACITOR

1 uF+/-10%,35 V,RADIAL

KEMET T350A105K035AT MOUSER 80-T350A105K035AT 5

C3,C29 CERAMICCAPACITOR

100 pF+/-10%, X7R, 200 V, RADIAL

MALLORY CK05BX101K MOUSER 539-CK05101K 2



C8,C9,C11,C12,C13

CERAMICCAPACITOR

0.01 uF+/-10%, X7R, 100 V, RADIAL


C4,C5,C15,C17,C19,C20,C26,C28

CERAMICCAPACITOR

10 pF+/-10%, X7R, 200 V, RADIAL

AVX CK05BX100K MOUSER 581-CK05BX100K 8

C6,C16 MICACAPACITOR

150 pF+/-5%,RADIAL

CORNELLDUBILIER CD10FD151JO3F MOUSER 598-

CD10FD151JO3F 2

C16(ALTERNATEPER CALIBRATIONPROCEDURE)

MICACAPACITOR

130 pF+/-5%,RADIAL

CORNELLDUBILIER CD15FD131JO3 MOUSER 5982-15-500V130 1

C7,C25 POLYPROPYLENEVARIABLE CAPACITOR 3.5 TO 40 pF SPRAGUE/

GOODMAN GYC40000 MOUSER 659-GYC40000 2

C10,C33,C37,C38,C40

TANTALUMCAPACITOR

10 uF+/-10%,20 V,RADIAL

VISHAY/SPRAGUE 199D106X9020C1V1E3 MOUSER 74-199D20V10-E3 5

C14 MICACAPACITOR

SELECTED PERCALIBRATIONPROCEDURE

. . . . 1

C21,C27 MICA CAPACITOR

330 pF+/-5%,RADIAL

CORNELLDUBILIER CD15FD331J03 MOUSER 5982-15-500V330 2

C21(ALTERNATEPER CALIBRATIONPROCEDURE)

MICACAPACITOR

300 pF+/-5%,RADIAL

CORNELLDUBILIER CD15FD301JO3F MOUSER 5982-15-500V300-

F 1

C24 MICACAPACITOR

SELECTED PERCALIBRATIONPROCEDURE

. . . . 1

C22,C23,C34,C35

CERAMICCAPACITOR

0.1 uF+/-10%, X7R, 50 V, RADIAL


C32,C39ALUMINUMELECTROLYTICCAPACITOR

220 uF+/-20%,10 V,RADIAL

XICON 140-XRL10V220-RC MOUSER 140-XRL10V220-RC 2

C36 TANTALUMCAPACITOR

0.47 uF+/-10%,35 V

VISHAY/SPRAGUE 199D474X9035A1V1E3 MOUSER 74-199D35V0.47-

E3 1

CR1,CR2,CR4,CR5,CR6

RECTIFIER (USE PART NUMBER) RECTRON 1N4001-B MOUSER 583-1N4001-B 5

CR3 DIODE (USE PART NUMBER)CENTRALSEMICON-DUCTOR

1N914 MOUSER 610-1N914 1

J1 JACK MONO, 1/4" SWITCHCRAFT 111X MOUSER 502-111X 1

J2 JACK STEREO, 1/4" SWITCHCRAFT 112BX MOUSER 502-112BX 1

L1,L2,L3,L4

INDUCTOR,THREE-SECTION,UNIVERSAL "PIE" WOUND

1 mH +/-5%,19 OHM,Q=59 @ 0.25 MHz,SRF=3.7 MHz MINIMUM

J.W. MILLER 4652 HARRISONINSTRUMENTS 96804-4652 4

Q1,Q2,Q6,Q7,Q11,Q12,Q16

TRANSISTOR PNP,TO-92 CASE

FAIRCHILDSEMICON-DUCTOR

2N3906BU MOUSER 512-2N3906BU 7

Q3,Q5,Q8,Q10,Q13

JUNCTION FIELD EFFECTTRANSISTOR N-CHANNEL, TO-92 CASE


2N5484 MOUSER 512-2N5484 5

Q4,Q9Q14,Q15 TRANSISTOR NPN,

TO-92 CASE


2N3904BU MOUSER 512-2N3904BU 4

R1,R24,R36

RESISTOR,CARBONFILM

3300 OHM+/-5%,1/4 WATT

XICON 291-3.3K-RC MOUSER 291-3.3K-RC 3

R2,R22,R35,R49,R52

RESISTOR,CARBONFILM

22K OHM+/-5%,1/4 WATT

XICON 291-22K-RC MOUSER 291-22K-RC 5

R3,R11,R17,R25,R37

RESISTOR,CARBONFILM

10K OHM+/-5%,1/4 WATT


R4,R13,R23,R38,R41,R44,R48,R55

RESISTOR,CARBONFILM

100K OHM+/-5%,1/4 WATT


R5,R20,R27,R33

RESISTOR,CARBONFILM

4.7M OHM+/-5%,1/4 WATT

XICON 291-4.7M-RC MOUSER 291-4.7M-RC 4

R6,R21,R28,R34

RESISTOR,CARBONFILM

2.7M OHM+/-5%,1/4 WATT

XICON 291-2.7M-RC MOUSER 291-2.7M-RC 4

R7,R14, RESISTOR, 2200 OHM



R15,R19,R29,R30,R31

CARBONFILM

+/-5%,1/4 WATT


R8,R9,R10,R39,R40,R42

RESISTOR,CARBONFILM

1M OHM+/-5%,1/4 WATT

XICON 291-1M-RC MOUSER 291-1M-RC 6

R12RESISTOR,CARBONFILM

150K OHM+/-5%,1/4 WATT



1000 OHM+/-5%,1/4 WATT



220K OHM+/-5%,1/4 WATT



68K OHM+/-5%,1/4 WATT


R32,R45RESISTOR,CARBONFILM

33K OHM+/-5%,1/4 WATT



680 OHM+/-5%,1/4 WATT

XICON 291-680-RC MOUSER 291-680-RC 1


220 OHM+/-5%,1/4 WATT



33 OHM+/-5%,1/4 WATT



4700 OHM+/-5%,1/4 WATT



10 OHM+/-5%,1/4 WATT


R56RESISTOR,METALFILM

20.0K OHM+/-1%,1/4 WATT


R57RESISTOR,METALFILM

3920 OHM+/-1%,1/4 WATT


RV1,RV2(NOTE 7) POTENTIOMETER

10K OHM+/-10%,LINEAR TAPER,CONDUCTIVEPLASTIC

CLAROSTAT 308N10K MOUSER 785-308N10K 2

SW1 SWITCH SPDT C & K 7101SYZQE MOUSER 611-7101-001 1

U1 INTEGRATEDCIRCUIT

(USE PARTNUMBER)

NATIONALSEMICON-DUCTOR

LP2951ACN/NOPB DIGI-KEY LP2951ACN-ND 1

. SOCKETFOR U1 8-POSITION, WIRE-WRAP® MILL-MAX 123-93-308-41-001000 MOUSER 575-293308 1

. PERFORATEDBOARD

GLASS-EPOXY, 17" X 8.5" X 0.062" VECTOR 169P84WE MOUSER 574-169P84WE 1

(NOTE 2) TERMINAL PRESS-FIT, SOLDER FORKTO WIRE-WRAP® VECTOR T68A/M

(PKG OF 1000) MOUSER 574-T68A/M(PKG OF 1000) 1

(ALTERNATETO ABOVE;AVAILABLE INPACKAGES OF 100)

TERMINAL PRESS-FIT, SOLDER FORKTO WIRE-WRAP® VECTOR T68/C

(PKG OF 100) MOUSER 574-T68/C 3

. BRAID, BUS 0.08" WIDEX 5' LONG CHEMTRONICS 80-3-5 MOUSER 5878-80-3-5 1

. KNOB, POTENTIOMETER

0.748"D,0.470"H,FOR 0.125"D SHAFT

ALCO PKES60B1/8 MOUSER 506-PKES60B1/8 2

.STANDOFF,CIRCUIT BOARDSUPPORT

4-40 THREAD,0.625" LONG,ALUMINUM

KEYSTONE 1808 MOUSER 534-1808 8

(ALTERNATETO ABOVE; FOR USE WITH T68TERMINALS)

STANDOFF,CIRCUIT BOARDSUPPORT

4-40 THREAD,0.750" LONG,ALUMINUM


.STANDOFF,PLASTIC COVERSUPPORT

4-40 THREAD,MALE/FEMALE0.625" LONG,ALUMINUM .


.STANDOFF,ANTENNASUPPORT

6-32 THREAD,0.500" LONG,NYLON

KEYSTONE 1903C MOUSER 534-1903C 8

(NOTE 1) BRACKET, CONTROL . . . . . 1

(NOTE 1) BRACKET, JACK . . . . . 1

(NOTE 1) PLATE, GROUND . . . . . 1

(NOTE 1) COVER, PLASTIC . . . . . 1



(NOTE 1) BASE, PLYWOODPLYWOOD,DOUGLAS FIR,GRADE A-D17" X 11" X 1/2"

. . . . 1

. HOLDER,9 VOLT BATTERY . KEYSTONE 79 MOUSER 534-079 1

(NOTE 1) MOUNTING PLATE,BATTERY HOLDER . . . . . 1

. CONNECTOR,9 VOLT BATTERY . KEYSTONE 72-8 MOUSER 534-72-8FB 1

. LUG, SOLDER NUMBER 4 KEYSTONE 7328 MOUSER 534-7328 1

. LUG, SOLDER NUMBER 6 KEYSTONE 7312 MOUSER 534-7312 2

(NOTE 3) WIRE, HOOK-UP

22 GAUGE,STRANDED,TEFLONINSULATED,WHITE

ALPHA 5855 WH005(ROLL OF 100') MOUSER 602-5855-100-01

(ROLL OF 100') 1

(NOTE 4) WIRE, WIRE-WRAP®

26 GAUGE,SOLID,KYNARINSULATED,BLACK

OK INDUSTRIES R26BLK-0100(ROLL OF 100') MOUSER 801-R26BLK

(ROLL OF 100') 1

(NOTE 5) WIRE, BUS16 GAUGE,TINNEDCOPPER

BELDEN/CDT 8013 000100(ROLL OF 100') MOUSER 566-8013

(ROLL OF 100') 1

(NOTE 6) TUBING, HEAT-SHRINK3/32" DIAMETER,POLYOLEFIN,BLACK

3M ELECTRONICSPECIALTY

FP301 3/32 BLACK 48"BK MOUSER 5174-13321

(4' LENGTH) 1

. MACHINE SCREW,ANTENNA MOUNTING

STAINLESS STEEL,PAN HEAD,PHILLIPS,6-32 X 5/16"

. . MCMASTER-CARR 91772A145 8

. WASHER, LOCK,ANTENNA MOUNTING

STAINLESSSTEEL,SPLIT-RING,#6,0.031" THK0.148" ID 0.250" OD


. WASHER, FLAT,ANTENNA MOUNTING

STAINLESS STEEL, #6,0.156"ID,0.312" OD,MS15795-805


. MACHINE SCREW,ANTENNA STANDOFF

NYLON,82° FLAT HEAD,SLOTTED,6-32 X 1/2"


. MACHINE SCREW,COVER MOUNTING

STAINLESS STEEL,PAN HEAD,PHILLIPS,4-40 X 3/8"


. WASHER, FLAT,COVER MOUNTING

NYLON,#4,0.115" ID, 1/4" OD, 0.062" THK


. MACHINE SCREW,CIRCUIT BOARD STANDOFF

STAINLESS STEEL,82° FLATHEAD,PHILlIPS,4-40 X 5/8"


. SELF-TAPPINGSCREW, BRACKET MOUNTING

STAINLESS STEEL,PAN HEAD,TYPE A,PHILLIPS,#4 X 3/8"


. SELF-TAPPING SCREW, BATTERYHOLDER MOUNTING


. .MCMASTER-CARR 92470A097 4

. SELF-TAPPING SCREW, FIXTUREMOUNTING



.FIXTURE,MICROPHONESTAND MOUNTING

5/8"-27 INTERNALTHREAD ATLAS SOUND AD-11B HARRISON

INSTRUMENTS 99999-AD-11B 1

Notes:

1) Fabricated item; refer to drawing2) 250 terminals required.3) Approximately 10' of hook-up wire required4) Approximately 40' of Wire-Wrap® wire required5) Approximately 2' of 16-gauge bus wire required



6) Approximately 4" of heat-shrink tubing required7) The potentiometers shafts are trimmed to a length of 3/8"

Kynar® is a registered trademark of Elf Atochem North America, Inc.Teflon® and Tefzel® are registered trademarks of E. I. du Pont de Nemours and Company.Wire-Wrap® is a registered trademark of Cooper Industries, Inc.

Photos(back to contents)

The following photos are of the 145 Theremin built by Keja Rowe, a student at the Roosevelt High School in Greenbelt, Maryland. Keja followed the prescribedconstruction method closely to build his theremin, which serves as a fine example of the instrument.

Closeup View of Circuit Board Large Overall View

Daniel from Switzerland crafted this elegant version of the 145 Theremin in an aero-plywood enclosure. The antennas can be folded over the top of the instrument,which has a clear cover for viewing the circuit.

Marcus Young, an engineering student, created this unusual version of the 145 Theremin inside an owl. Marcus sectioned the circuit into three printed circuit boards,and placed the antennas in the owl's wings. In addition, clusters of blue light-emitting diodes illuminate the owl's eyes.



Roy from Edinburgh, Scotland, built this excellent 145 Theremin in a contemporary wood enclosure and with a rod pitch antenna which he reports works well. Theright photo shows the rear of the instrument, where an added ground post permits good grounding of the instrument when played through a battery-poweredamplifier. You can see Roy playing his theremin here.

Text and drawings ©2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009 , 2011, 2012 by Arthur Harrison

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