102 Minimum Theremin Assembly Instructions

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These instructions contain steps to assemble these Harrison Instruments 102 Minimum Theremin Kit products:

102-KIT - Complete kit with all the parts to construct a 102 Minimum Theremin
102-PCBKIT1 - Unpopulated printed circuit board (PCB) with user-soldered, on-board components
102-PCBKIT2 - Unpopulated printed circuit board (PCB) with user-soldered on-board and off-board components

IMPORTANT: Please CLICK HERE TO READ SAFETY INFORMATION before proceeding.

Before you begin, verify that all the parts have been included in your kit. Click on the link that matches your kit's product number:

102-KIT

102-PCBKIT1

102-PCBKIT2

Beginners are encouraged to learn about proper soldering techniques before assembling this kit. Internet instructional videos on the topic are available:

Curious Inventor
Basic Soldering Lesson 1 - "Solder & Flux" (PACE, Incorporated; 8 additional lessons available)

Click here for images of a properly soldered kit.


Click here for the 102 Minimum Theremin Troubleshooting Guide.
The troubleshooting guide contains valuable advice that will be helpful to you in your construction.
It is recommended that you read this guide before you begin soldering.

You will need:

1. One of the 102 Minimum Theremin Kit products:  102-KIT, 102-PCBKIT1, or 102-PCBKIT2

2. Tools, available from distributors such as All-Spec Industries, Allied Electronics, and Mouser Electronics:

• Wire Strippers, such as Xcelite type 100X
• Diagonal Cutters, such as Xcelite type MS54J
• Long-Nose Pliers, such as Xcelite type LN54
• #1 Phillips Screwdriver, such as Xcelite type X101
• 1/8" Flat-Blade Screwdriver, such as Xcelite type R186
• 5/16" Nut Driver, such as Xcelite type HS10
• 3/8" Nut Driver, such as Xcelite type HS12
• 7/16" Nut Driver, such as Xcelite type HS14
• 1/2" Nut Driver, such as Xcelite type HS16
• Adjustable Wrench, such as Xcelite type 46CG
• Small-wattage Soldering Iron Station, such as Weller type WTCPT
• Solder
  Tin/Lead Alloy, such as Kester type 24-6337-0027: 63% Tin - 37% Lead, with Rosin Core, 0.031" diameter
  or
  Tin/Silver/Copper Alloy, such as Kester type 24-7068-1402: 96.5% Tin - 3% Silver - 0.5% Copper, with Rosin Core, 0.031" diameter
  
  
  

  Choosing the Type of Solder Either Tin/Lead Alloy solder, or Tin/Silver/Copper Alloy solder may be used to construct this kit. Tin/Silver/Copper Alloy solder was introduced in the early 2000s to comply with an environmental directive known as the Restriction of Hazardous Substances Directive, "RoHS." Click here for more information on the RoHS directive. All the parts in this kit are compliant with the RoHS directive. However, the finished kit will not be in compliance with the RoHS directive if it is constructed with Tin/Lead Alloy solder. There are differences between the two solder types: Tin/Silver/Copper Alloy solder requires a higher melting temperature than Tin/Lead Alloy solder, and persistent application of excessive heat may damage the kit's printed circuit board and components. The flow characteristic and adhesion of Tin/Silver/Copper Alloy solder is inferior to that of Tin/Lead Alloy solder, making it more difficult to apply. Tin/Silver/Copper Alloy connections are duller than connections made with Tin/Lead Alloy solder and are harder to evaluate for reliability because of their clumpy, granular appearance. The successful use of of Tin/Silver/Copper Alloy solder generally requires a greater degree of experience than the use of Tin/Lead Alloy solder. Tin/Lead Alloy solder, when used responsibly, poses no health threat to the kit builder or user, and is generally recommended. However, the responsible use of either type of solder includes the following precautions: 1) Do not put solder in your mouth. 2) Do not put your hands in your mouth or rub your eyes after handling solder. 3) Wash your hands thoroughly with soap and water after handling solder. 4) Use a temperature-controlled soldering iron that limits soldering temperatures to 700ºF (371ºC). 5) Provide adequate air-flow and ventilation to remove solder flux fumes from your workplace. 6) Wear safety glasses and suitable clothing to protect your eyes and body from hot solder. IMPORTANT: Regardless of the type of solder alloy you choose, only use solder with a rosin core. Do not use "water soluble flux" or "acid flux" core types.

  
  

Assembly Instructions

1. Mild Oxidation of the printed circuit board (PCB) solder pads may have occurred during storage or transit. To clean them, gently rub the pads with an unused pencil eraser. Remove any eraser residue with a clean, lint-free cloth.

2. In the following steps, you will solder the components to the PCB. This image illustrates the completed PCB, and may be used as a reference.
   
   In the illustration, the COMPONENTS table uses abbreviations: "uF" means microfarads, "pF" means picofarads, "nF" means nanofarads, and "K" means 1000. As examples, "0.047uF" is verbalized as "Zero point zero four seven microfarads, and "150K OHMS" is verbalized as "One-hundred-fifty-thousand ohms."
   
   

3. Attach a hexagonal standoff to each corner of the PCB with a 4-40 x 0.312"L screw, as illustrated. The screws are inserted into the PCB's component side, which is the side with the white printing. The hexagonal standoffs extend from the PCB's bottom side. The hexagonal standoffs elevate the board from the work surface to allow the easy insertion of components.
   
   

4. Form the leads of Resistor R1 with long-nose pliers, as shown. (Note that R1 has a SELECTED VALUE. Its ohm-value is selected at the factory to best-match the characteristics for the circuit. Therefore, R1's first three color bands will vary from kit to kit, and these three bands are shown here as white only for the purpose of illustration.)
   
   
   

5. Insert resistor R1 into the PCB at the location marked "R1." Note that the resistors in this kit may be oriented in either direction. However, it is good practice to orient them so that the color bands representing their values are read from left to right.  Click here for a Resistor Identification Guide.
   
   
6. Cut off the resistor's excess lead lengths, leaving about 1/16th inch of each lead extending from the board's bottom, as shown in "METHOD 1," below. If you desire, you may bend the resistor's leads against the board's pads, as shown in "METHOD 2," and then cut them. Doing so will help keep the resistor in place when the board is turned over for soldering. The same choice of these two methods applies to all the other components. The disadvantage of METHOD 2 is that a component will be harder to remove in the event that it has to be replaced. If you choose METHOD 2, make sure that the bent-over leads do not touch each other or adjacent leads or solder pads. Save two of the cut-off resistor leads to make a jumper for step 20 and optional step 24.
   
   
   
   
7. Solder resistor R1 in place. If you used "METHOD 1," above, you can solder one or both of the leads on the top side of the board to keep it in place. Then, turn the board over to solder both leads on the bottom side. Top-soldering the leads is optional, but useful for keeping the resistor from falling out of the board when METHOD 1 is used. For either method, it is standard practice to always solder the leads on the bottom of the board.
   
   Note: If desired, flux residue from solder may optionally be removed from the PCB with 90% Isopropyl Alcohol, applied with the gentle scrubbing action of a toothbrush. Absorb the used alcohol with a paper towel, and repeat as required until all the flux is removed. Flux removal will be easier if done shortly after connections are soldered. Confine scrubbing only to the solder pad areas, as directly scrubbing components may remove their markings or otherwise damage them. Flux may also be removed from other soldered connections, such as the terminals on controls and jacks, with a brush and alcohol. However, be sure to keep the alcohol confined to the part being cleaned by using adequate absorbent paper towel as a "dam" to prevent it from spreading to adjacent surfaces.  WARNINGS: Isopropyl Alcohol is highly flammable, and should be kept away from heat sources such as soldering irons. Use Isopropyl Alcohol in a well-ventilated area. Do not use the toothbrush for personal hygiene after it is used for PCB cleaning.
   
   
8. Repeat steps 5 through 8 for the remaining 12 resistors, using the illustration in step 2 as a guide.
   
   
9. Prepare the leads of capacitors C1, C2, C3, C4, C6, C12, and C15 the same way the resistors were prepared, and solder them in their respective locations on the PCB. These capacitors may be oriented in either direction, however, it is good practice to orient them so that their second line of numerical markings face upward, read from left-to-right. The second line of markings are three digits followed by a letter, and designate the capacitor value and accuracy. (The first line represents the manufacturer, voltage, and the kind of material used to make the capacitor. The third line is a lot code, and will vary, as will the fourth line, which is a coded date of manufacture.) IMPORTANT: These capacitors are very delicate. Do not apply excessive force to their leads. Make sure the capacitors fit easily into the PCB before soldering, because any tension on the leads will cause them to break off the capacitor body while being soldered.
   
   
   
   
10. In the next steps, rectifier CR1 and four integrated circuits (U1, U2, U3, and VR1) will be installed into the PCB. IMPORTANT: These are semiconductor devices that are sensitive to static electricity. Static electricity is a charge that accumulates on your body's surface and on other objects. You can often observe static electricity's effect when you touch a doorknob or other metal object and feel a brief jolt in your hand. While usually harmless to people, it can destroy semiconductors such as those used in this kit. To prevent damage to these semiconductors, discharge static electricity from your body by touching a grounded metal object near your workstation before removing the semiconductors from their conductive foam pad or conductive bag. Unwrap the semiconductors at your workstation, and install them in the PCB immediately. Click Here for Component Handling Precautions.
    
    
11. The CR1 rectifier that comes with your kit may have adhesive tabs attached to their leads. If so, cut them off as shown:
    
    
    
    Form the leads of rectifier CR1 as shown:
    
    
    
    
12. Insert rectifier CR1 into the PCB at the locations marked "CR1." IMPORTANT: Rectifier CR1 must be inserted in the correct direction. Make sure that its CATHODE LEAD is inserted into the PCB hole with the SQUARE PAD, closest to the right edge of the PCB. As shown in the picture, the cathode lead is the lead designated by the CATHODE DESIGNATOR band on the rectifier's body. Cut off the rectifier's excess lead lengths, leaving about 1/16th inch of each lead extending from the board's bottom. Once CR1 is correctly inserted, solder it in place.
    
    
13. Refer to the following picture of integrated circuits U1 and U2. Note the notch that designates the end of the device with pins 1 and 14. The ICs may be supplied with their pin rows angled slightly apart. To facilitate their insertion into the PCB, gently form the pin rows so that they are 90 degrees (perpendicular) with relation to the body of the IC. This may be done by carefully pressing each row against a flat surface (such as a tabletop) just enough to bend them perpendicular with the body.
    
    
    
    
14. Insert ICs U1 and U2 into the PCB at the locations marked "U1 and U2." IMPORTANT: U1 and U2 must be inserted in the correct direction. Make sure that pin 1 is inserted into the upper-left PCB hole with the SQUARE PAD. As shown in the picture, the end of the IC with pin 1 is designated by the U-shaped notch on the IC's body. Do not confuse the U-shaped notch with the circular recess that may be present at the other end of the IC's package. Before soldering the ICs into place, verify that they are oriented correctly and that none of the pins have been bent, which would prevent them from going through their holes. Once the ICs are correctly inserted, solder them in place. Solder two of each of the IC's pins on the top side of the board to keep them in place; for example, pins 7 and 14. Then, turn the board over to solder all the pins on the bottom side. IMPORTANT: Avoid excessive heat when soldering U1 and U2.
    
    
15. Refer to the following picture of integrated circuit U3. As with the previous two ICs, gently form U3's pin rows so that they are perpendicular with relation to the body of the IC. Insert IC U3 into the PCB at the location marked "U3." IMPORTANT: U3 must be inserted in the correct direction. Make sure that pin 1 is inserted into the upper-left PCB hole with the SQUARE PAD. As shown in the picture, the end of the IC with pin 1 is designated by the circular recess on the IC's body. Before soldering U3 into place, verify that it is oriented correctly and that none of its pins have been bent, which would prevent them from going through their holes. Once U3 is correctly inserted, solder it in place. Solder two of U3's pins on the top side of the board to keep it place; for example, pins 4 and 8. Then, turn the board over to solder all the pins on the bottom side. IMPORTANT: Avoid excessive heat when soldering U3.
    
    
    
    
16. Form the leads of integrated circuit VR1 with long-nose pliers as shown. IMPORTANT: The regulator leads are brittle and will break easily. Form the leads gently, avoiding excessive plier pressure and sharp bends.
    
    
    
    
17. Insert VR1 into the PCB at the location marked "VR1." IMPORTANT: VR1 must be inserted in the correct direction. Make sure that pin 1 is inserted into the PCB hole with the SQUARE PAD closest to the left edge of the PCB. As shown in the picture, pin 1 is the pin on the left when VR1 is oriented with the flat surface facing you and the pins are pointing downward. Cut off VR1's excess lead lengths, leaving about 1/16th inch of lead extending from the board's bottom. Once VR1 is correctly inserted, solder it in place. IMPORTANT: Avoid excessive heat when soldering VR1.
    
    
18. Insert pitch zero trimmer potentiometer RV1 into the PCB at the location marked "RV1." The adjusting screw of the potentiometer is closest to the bottom edge of the board. Once RV1 is correctly inserted, solder it in place, making sure that it is held flat against the board.
    
    
19. Insert Capacitors C5, C7, C8, C9, C10, C11, C13 and C14 into the PCB at their respective locations. Refer to the illustration below to identify their positive (+) leads. IMPORTANT: These eight capacitors must be inserted in the correct direction. Make sure that their longer (+) leads are inserted into the PCB holes with the SQUARE PADS closest to the right edge of the PCB. Cut off the capacitors' excess lead lengths, leaving about 1/16th inch of each lead extending from the board's bottom. Solder them in place.
    
    
    
    
20. Refer to the illustration below to form a piece of resistor lead saved from step 6 into a "U" shaped jumper, and insert it between the two pads marked GND in the lower-right of the PCB. Cut off the excess lead lengths, leaving about 1/16th inch of each lead extending from the board's bottom. Solder the jumper in place.
    
    
    
    A second jumper may be soldered between the two pads marked "INH," located to the left of U3. This will disable the SPEAKER output for your theremin by shutting-down the U3 amplifier IC, and reduce battery drain. If you do not plan to connect a loudspeaker directly to the PCB's SPEAKER pads, and only require an output from LINE OUT, you may insert this jumper. Do not insert this jumper if the PCB will be used to directly drive a loudspeaker.
    
    
21. All of the components have now been attached to the PCB. Inspect each soldered connection carefully to ensure that there are no solder bridges between adjacent pads, pads with excess solder, or insufficient solder. Ensure that the three ICs, voltage regulator, rectifier, and capacitors C5, C7, C8, C9, C10, C11, C13 and C14 are inserted in the correct direction.
    
    

    For product number 102PCB-KIT1, you have completed your kit. For product number 102PCB-KIT2, the following steps will provide instructions for adding the peripheral parts to your circuit board. For product number 102-KIT, skip steps 22 through 25, and proceed with step 26. IMPORTANT: Do not perform steps 22 through 25 for product number 101-KIT.

    
    
22. With the exception of the antenna wire, the lengths of the wires connecting the PCB to the off-board components are not critical, and should be selected for your choice of enclosure and control locations. Plan in advance by making the wires long enough to allow the circuit board be to mounted as desired, with the peripheral parts mounted through the enclosure's side or sides. Note that 102PCB-KIT2 is provided with 4 feet of hookup wire, which should be an ample amount for any reasonable arrangement.
    
    Pay careful attention to the connection order for all the wires. The wire pairs going to the power switch and speaker, however, may be connected in either order.
    The PCB should be mounted in a position that permits the adjustment of the pitch zero trimmer potentiometer ("ZERO CAL" trimmer).
    
    Refer to the illustration below. Using hookup wire, connect the pitch control, output jack, ground jack, loudspeaker, power switch, and volume control to the PCB. The battery connector is furnished with red (+) and black (-) wires that are also soldered to the PCB. Note the detail in the lower-left of the drawing illustrating how the wires are attached to the PCB. Passing the insulated part the wires through the strain relief holes will prevent them from breaking off the solder pads. Note that the output jack has two solder lugs, one called the "tip lug," and the other the "sleeve lug." These must not be interchanged. The lugs can be identified by their different shapes:  is the tip and  is the sleeve. The sleeve lug may also be identified as the one with "SWITCHCRAFT" stamped into the metal where it extends from the jack. The tip lug is connected to the "LINE OUT" pad on the PCB, and the sleeve lug is connected to the "GROUND" pad on the PCB.
    
    You may connect wire to the antenna jack now, but don't solder the other end of its wire to the PCB until it is mounted through the wall of your enclosure, since this jack cannot pass through the enclosure wall from the rear.
    
    The antenna wire length should be just enough to go between the antenna jack and the PCB, plus a little slack. If you are providing your own metal enclosure, be sure that the wire between the antenna jack and the PCB isn't pressed against a metal surface. Excessive antenna wire length, or locating the antenna wire too close to metal parts has the effect of increasing the amount of capacitance presented to the theremin circuit's antenna input. Excessive capacitance will prevent the theremin from functioning.
    
    
    
    
23. Attach knobs to the pitch control and volume control with the allen keys provided. The knobs have a white index line which indicate the control's degree of rotation. You may position the index line so that it is approximately in the 7 o'clock position when the control shaft is fully counterclockwise, and approximately in the 5 o'clock position when the shaft is fully clockwise. Once the controls are mounted to an enclosure, the knobs may be repositioned as needed. Power will be "ON" when the switch toggle in the "UP" position, as illustrated. The top switch lug is not connected. The power switch wires may be interchanged without affecting operation.
    
    
24. Some builders may use the theremin only to drive an external amplifier/speaker system, and not require the speaker furnished with the kit. In this case, battery life may be improved considerably by inserting a jumper formed from a piece of resistor lead saved from step 6 between the two pads marked "INH" located to the left of U3. Cut off the excess lead lengths, leaving about 1/16th inch of each lead extending from the board's bottom. Solder the jumper in place. Do not insert this jumper for the normal operation of the theremin with the supplied speaker.
    
    

    For product number 102PCB-KIT2, you have completed your kit.

    
    
25. The following steps provide instructions to attach parts, including the PCB, to the front panel, and to wire them together.
    
    
26. Use these illustrations as a reference in attaching parts to the front panel.
    
    
    
27. In the next two steps, you will attach the controls to the panel. Your kit comes with two different controls. They have very similar appearances, but different ohm values. They must not be interchanged. Identify the VOLUME control, which has "A10K" printed directly above its threaded bushing, as shown below.
    
    
    
    Remove the nut and two washers from the VOLUME control's bushing. Referring to the "Front Panel, Rear View" illustration in step 26, insert the VOLUME control into the appropriate panel hole through the rear of the panel, aligning the control's anti-rotation tab with the anti-rotation hole. Referring to the illustration below, fasten the control in place with the nut and washers. Place both washers on the threaded bushing, followed by the nut. Tighten the nut with a 7/16" nut driver.
    
    
    
    
28. Identify the PITCH control, which has "B1K" printed directly above its threaded bushing, as shown below.
    
    
    
    Remove the nut and two washers from the PITCH control's bushing. Referring to the "Front Panel, Rear View" illustration in step 26, insert the PITCH control into the appropriate panel hole through the rear of the panel, aligning the control's anti-rotation tab with the anti-rotation hole. Referring to the illustration below, fasten the control in place with the nut and washers. Place both washers on the threaded bushing, followed by the nut. Tighten the nut with a 7/16" nut driver.
    
    
    
    
29. The OUTPUT jack is supplied with a nut, flat washer, and internal-tooth lockwasher. Referring to the illustration below, place the lockwasher on the jack's bushing, then insert the jack into the appropriate panel hole through the rear of the panel.  Place the flat washer on the jack's bushing, followed by the nut. Position the jack so its solder lugs are closest to the vertical edge of the panel. Tighten the nut with a 1/2" nut driver. Tighten the nut firmly. The teeth of the lockwasher must pierce the non-conductive finish on the front panel so that the jack makes good electrical contact to the panel.
    
    
    
    
30. The POWER switch is supplied with two nuts, a lockwasher, and an anti-rotation washer. The anti-rotation washer is illustrated below.
    
    
    
    Referring to the illustration below, place one of the two nuts on the switch bushing, and finger-tighten the nut until it is flush with the switch body. Then, place the lockwasher on the bushing. Insert the POWER switch into the appropriate panel hole through the rear of the panel. Next, place the anti-rotation washer on the bushing, engaging the washer's inner tab in the switch's bushing groove and the washer's outer tab in the panel's anti-rotation hole. Then, place the second nut on the bushing. Make sure that the switch and anti-rotation washer are correctly aligned with the panel's anti-rotation hole, and tighten the second nut with a 1/4" nut driver.
    
    
    
    
31. Wires will now be soldered to the panel components. To assist in this step, you may temporarily remove the four hexagonal standoffs and screws from the PCB, and temporarily attach them to the front of the panel to keep the assembly level on your work surface.
    
    Prepare eleven 2 1/2" lengths of hookup wire as illustrated below. Strip 1/4" of insulation from one end of each wire. Make sure that the individual strands of the wire remain twisted together. Pre-coat ("tin") the stripped ends with a small amount of solder. Form each stripped end into a hook. Solder three wires to the VOLUME control, three wires to the PITCH control, two wires to the OUTPUT jack, and two wires to the POWER switch. Insert the wire hooks through the holes in the lugs, and gently squeeze them closed with pliers, so that the wires remain in place during soldering. Only two wires are soldered to the POWER switch. Do not solder a wire to the switch lug located closest to the VOLUME control. The remaining 2 1/2" wire will be used in step 33.
    
    
    
    
32. Referring to the illustration below, attach the antenna jack to the antenna jack bracket with a 5/16" nut driver. Make sure the nut is sufficiently tight, but do not strip the plastic threads.
    
    
    
    
33. Referring to the illustration below, solder the wire prepared in step 31 to the antenna jack lug. Trim the length of the wire to 1 1/2". Strip 1/8" of insulation from the wire. Make sure that the individual strands of the wire remain twisted together. Pre-coat ("tin") the stripped ends with a small amount of solder.
    
    
    
    
34. Attach the antenna jack bracket to the rear of the panel as illustrated in step 26, using two #4-40 x 0.312" pan-head screws.
    
    
35. The GND (ground) jack is supplied with a nut, solder lug, and internal-tooth lockwasher. The solder lug will not be used. Insert the GND jack into the appropriate panel hole through the front of the panel. Referring to the illustration below, place the lockwasher on the jack's threaded bushing, followed by the nut. Tighten the nut with a 3/8" nut driver. Tighten the nut firmly while holding the jack's front with an open-ended or adjustable wrench. The teeth of the lockwasher must pierce the non-conductive finish on the front panel so that the jack makes good electrical contact to the panel.
    
    
    
    
36. Twist the battery connector's wires together, and trim them to a length of 4". Strip 1/8" of insulation from each of the wires. Referring to the illustration below, solder the battery connector to the PCB assembly that was completed in step 21. The battery connector is furnished with red (+) and black (-) wires. IMPORTANT: Be careful not to interchange the battery connector wires. Note the illustration detail showing how the wires are attached to the PCB. Passing the insulated part the battery connector wires through the strain relief holes will prevent them from breaking off their solder pads.
    
    
    
    
37. Remove the four hexagonal standoffs and screws that were temporarily attached to the panel in step 31. Refasten them to the PCB as illustrated in step 3. Set the PCB assembly aside.
    
    
38. Prepare two 3 1/2" lengths of hookup wire as illustrated below. Strip 1/4" of insulation from one end of each wire. Make sure that the individual strands of the wire remain twisted together. Pre-coat ("tin") the stripped ends with a small amount of solder. Form the stripped ends into a hook.
    
    
    
    
39. Referring to the illustration below, solder one wire to each of the two speaker terminals. Insert the wire hooks through the holes in the lugs, and gently squeeze them closed with pliers, so that the wires remain in place during soldering. Lay the wires in the direction illustrated, and twist them together.
    
    
    
    
40. Referring to the illustration below, attach the speaker and battery holder to the panel with four #6-32 x 0.375" pan head screws, four #6 lockwashers, and four #6-32 hex nuts. As shown, the two top screws fasten both the speaker and the battery holder. The two sets of bottom screws, washers, and nuts are hidden from view.
    
    
    
    
41. Attach the PCB's standoffs to the panel using four #4-40 x 0.312" pan-head screws. Position the PCB as indicated in the illustration below.
    
    
    
    
42. The free ends of the panel component wires will now be soldered into holes on the PCB. The holes are outlined with labeled white rectangles. (Note that the hole labeled "GROUND" is not used.) Only the smaller hole within each rectangle will be used to solder the wire. The larger stress-relief holes will not be used. Each wire will enter the hole from the bottom of the PCB and solder will be applied to the top of the PCB.
    
    Start with the speaker wires. Strip 1/8" of insulation from one end of each wire. Make sure that the individual strands of the wire remain twisted together. Pre-coat ("tin") the stripped ends with a small amount of solder. Insert each speaker wire into one of the solder pad holes on the PCB labeled SPEAKER. Solder the wires in place.
    
    
43. Repeat the above procedure for the switch wires. Insert each switch wire into one of the solder pad holes on the PCB labeled SWITCH. Solder the wires in place.
    
    
44. Strip 1/8" of insulation from one end of each wire from the VOLUME control and tin them. Solder the VOLUME control wires to the solder pad holes on the PCB labeled VOL CCW, SLIDER, and VOL CW. These wires must be connected in the order illustrated below. Solder the wires in place.
    
    
    
    
45. Strip 1/8" of insulation from one end of each wire from the PITCH control and tin them. Insert the PITCH control wires to the solder pad holes on the PCB labeled ZERO CCW, SLIDER, and ZERO CW. These wires must be connected in the order illustrated below. Solder the wires in place.
    
    
    
    
46. Strip 1/8" of insulation from one end of each wire from the OUTPUT jack and tin them. Insert the OUTPUT jack wires into the solder pad holes on the PCB labeled LINE OUT and GROUND. These wires must be connected in the order illustrated below. Solder the wires in place.
    
    
    
    
47. Insert the antenna jack wire into the solder pad hole on the PCB labeled ANT. Solder the wire in place.
    
    
48. Attach knobs to the pitch control and volume control with the allen keys provided. The knobs have a white index line which indicate the control's degree of rotation. Position the index line so that it is approximately in the 7 o'clock position when the control shaft is fully counterclockwise, and approximately in the 5 o'clock position when the shaft is fully clockwise.
    
    
49. Assemble the antenna using the illustration below as a guide.
    
    a. Screw the banana plug onto one end of the threaded rod. Do not use any tools to tighten the plug; it only has to be finger-tight.
    b. Slide the banana plug housing onto the rod with its internal-threaded end downward, and screw it onto the banana plug. The housing also only has to be finger-tight.
    c. Slide flat washer #1 onto the rod.
    d. Slide the split-ring lockwasher onto the rod.
    e. Thread nut #1 onto the rod, and advance it all the way down to the lockwasher. Hold the banana plug housing firmly and tighten the nut with an adjustable wrench.
    f. Thread nut #2 onto the rod, advancing it about 1/4" from the top.
    g. Slide the inside-tooth lockwasher onto the rod.
    h. Slide the plate onto the rod.
    i. Slide flat washer #2 onto the rod.
    j. Thread nut #3 onto the rod.
    k. Hold nut #2 with an adjustable wrench, and tighten nut #3 with a 5/16" nut driver.
    
    Set the antenna assembly aside.
    
    
    
    
    

    Proceed to the Calibration Instructions that follow.

    
    
    

Calibration Instructions

A basic understanding of the one of the theremin's operating principles, described in the box below, will be helpful when performing the calibration.

The calibration procedure will ensure that the theremin responds correctly to hand positions. The procedure is performed with the case removed. After the calibration is complete, the case will be attached, and the theremin will be ready for use.

1. Set the POWER switch to the down (off) position.
   
2. Set the VOLUME control and the PITCH control to their middle (12 o'clock) positions.
   
3. Attach the 9V battery to the battery connector, and secure the battery in the holder.
   
4. Using a small flat-blade screwdriver, set the ZERO CAL potentiometer on the PCB to its extreme counterclockwise position by turning the slotted adjustment screw 15 full counterclockwise rotations. This ensures that it is set at the beginning of its adjustment range. Note that the potentiometer's mechanism has an internal slip clutch, so it can safely be turned an unlimited number of times in either direction.
   
   
   
   
5. Insert the Antenna into the antenna jack.
   
6. Set the POWER switch to the up (on) position.
   
7. With one hand, hold the theremin assembly securely by the top and bottom edges of the front panel, in an elevated position. Hold the theremin so that you are facing the ZERO potentiometer, and so that the antenna plate is positioned away from you. Keep the antenna at least 4 feet away from nearby objects. Positioning the theremin in this way enables access screwdriver access to the ZERO potentiometer.
   
8. With your other hand, using the small screwdriver, slowly turn the ZERO CAL potentiometer clockwise.
   
9. As the ZERO CAL potentiometer is rotated, a very high pitch will become evident. The pitch will become successively lower with continued rotation, until it stops abruptly. Stop turning the potentiometer at this point.
   
10. Remove the screwdriver from the potentiometer. Note that the pitch might return; this is a normal condition resulting from the capacitance change that occurs when the screwdriver is removed.
    
11. Adjust the PITCH control just to the point where the pitch stops. This point may occur either slightly clockwise or counterclockwise of its center position.
    
12. Starting from a distance of about two feet, move your hand toward the antenna. Note that the pitch commences at its lowest frequency with your hand about 18 inches away, increasing as the distance shortens.
    
13. The ZERO CAL potentiometer may be readjusted a few degrees in either direction, as required, until the "zero beat" condition coincides with a hand distance of 18 inches when the PITCH control is exactly in the 12 o'clock position.

Turn the power switch off and remove the antenna.

Place the theremin into the case with the antenna jack adjacent to the hole in the case's top.

Secure the panel to the case with a #4-40 x 0.375" flat-head screw in each corner.

Insert the antenna.

Your Harrison instruments Model 102 Theremin is complete! If you have any problems with your theremin, please e-mail us at sales@harrisoninstruments.com, and we will be happy to resolve any difficulties.

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The 102 Minimum Theremin design is used by licensed agreement with its owner. Specifications may change without notice. The purchase of these products from Harrison
Instruments or a third party does not convey a license to the buyer.

20161204