RCA Theremin Bill of Materials

The component numbering system is from our modernized schematic/Art Harrison's RCA Theremin write up. Component values are taken from the original RCA Theremin Service Notes, the RCA Theremin Replacement Parts document, Art Harrison's write up, or measured from original RCA Theremins directly.

Vacuum Tubes

Name Location Description
V1 UY-227 chassis Variable Pitch Oscillator
V2 UY-224 chassis Detector Modulator
V3 UY-227 chassis Fixed Pitch Oscillator
V4 UY-227 chassis 1st A.F. Amplifier
V5 UX-120 chassis Volume Control
V6 UX-171A chassis Volume Control Oscillator
V7 UX-171A chassis Power A.F. Amplifier
V8 UX-280 SPU Full-Wave Rectifier

Transformers

Value Location Description Value Source
T1 SPU Power Transformer
T2 ~55 µH chassis volume oscillator coil (inner winding) Measured from theremin
~60 µH chassis volume oscillator coil (outer winding) Measured from theremin
T3 ~12 mH 10" coil form volume control resonant coil Measured from theremin
~15 µH 10" coil form volume control pickup coil Measured from theremin
T4 ~1k Ω chassis A.F. Transformer, GW-42 (primary) Measured from theremin
~5k Ω chassis A.F. Transformer, GW-42 (secondary) Measured from theremin
T5 speaker RCA 106 Loudspeaker output transformer
T6 ~175 µH chassis pitch reference oscillator coil (inner winding) Measured from theremin
~195 µH chassis pitch reference oscillator coil (outer winding) Measured from theremin
T7 ~1k Ω chassis A.F. Transformer, GW-42 (primary) Measured from theremin
~5k Ω chassis A.F. Transformer, GW-42 (secondary) Measured from theremin
T8 ~175 µH chassis variable oscillator coil (inner winding) Measured from theremin
~195 µH chassis variable oscillator coil (outer winding) Measured from theremin
T9 ~30 mH 12" coil form Pitch control resonant coil Measured from theremin
~20 mH under 12" coil Pitch concentrated coil Measured from theremin

Resistors

Value Wattage Location Type Value Source
R1 2,250 Ω SPU wire wound plate Service Notes
R2 14.3K Ω 1 W SPU dogbone resistor Service Notes
R3 20K Ω 3 W SPU dogbone resistor Service Notes
R4 30 Ω (~14 Ω) SPU center-tapped wire wound Replacement Parts (Measured)
R5 30 Ω (~14 Ω) SPU center-tapped wire wound Replacement Parts (Measured)
R6 550 Ω chassis, multigang position 4 multigang wire wound Service Notes
R7 30 Ω (~14 Ω) SPU center-tapped wire wound Replacement Parts (Measured)
R8 30 Ω (~14 Ω) SPU center-tapped wire wound Replacement Parts (Measured)
R9 1000 Ω chassis, multigang position 1 multigang wire wound Service Notes
R10 625 Ω chassis, multigang position 2 multigang wire wound Service Notes
R11 420 Ω chassis, multigang position 3 multigang wire wound Service Notes
R12 100K Ω 1 W chassis, under multigang resistor dogbone resistor Service Notes
R13 250K Ω 1 W chassis, between G(V7) & GND dogbone resistor Service Notes
R14 10K Ω chassis, multigang position 5 multigang wire wound Service Notes
R15 5K Ω 1 W chassis, between C7 and C17/C21 dogbone resistor Service Notes
R16 10K Ω 1 W chassis, between SG(V2) & G(V1) dogbone resistor Service Notes
R17 5K Ω 1 W chassis, between C15 and C17/C21 dogbone resistor Service Notes

Capacitors

Value Location Type Description/Function Value Source
C1 2 MFD SPU paper/film filter capacitor Service Notes
C2 2 MFD SPU paper/film filter capacitor Service Notes
C3 0.5 MFD SPU paper/film filter capacitor Service Notes
C4 0.5 MFD SPU paper/film bypass capacitor Service Notes
C5 0.5 MFD SPU paper/film bypass capacitor Service Notes
C6 2 MFD chassis paper/film bypass capacitor Service Notes
C7 2 MFD chassis paper/film bypass capacitor Service Notes
C8 2200 pF volume coil mica DC blocking capacitor Art Harrison
C9 1 MFD chassis mica bypass capacitor Service Notes
C10 135 pF chassis, front panel air variable volume control adjustment Service Notes
C11 100 pF chassis mica trimmer volume trimmer Art Harrison
C12 ~580 pF chassis mica fixed tuning capacitor (volume) Replacement Parts
C13 0.5 MFD chassis paper/film bypass capacitor Service Notes
C14 0.02 MFD SPU, output jacks mica fixed capacitor Service Notes
C15 2 MFD chassis paper/film bypass capacitor Service Notes
C16 55 pF chassis, front panel air variable pitch control adjustment Service Notes
C17 0.5 MFD chassis paper/film center-tapped capacitor Service Notes
C18 100 pF chassis mica trimmer fixed pitch trimmer Art Harrison
C19 ~1160 pF chassis mica fixed tuning capacitor (fixed pitch) Replacement Parts
C20 2200 pF pitch coil mica DC blocking capacitor Art Harrison
C21 0.5 MFD chassis paper/film center-tapped capacitor Service Notes
C22 100 pF chassis mica trimmer variable pitch trimmer Art Harrison
C23 ~1200 pF chassis mica fixed tuning capacitor (variable pitch) Replacement Parts

Pilot Lamp

Type Voltage Amperage Location Description
I1 No. 40 6 v 0.15 amp chassis T-3 bulb, miniature base