R.C.A. Victor Co., Inc. 12-2 Schematic

R.C.A. Victor Co., Inc. 12-2

Get a print!

$8.00
Product Information:
Model:12-2
Manufacturer:R.C.A. Victor Co., Inc.

Schematics Content

Page 2:

RCA-VICTOR CO., INC.

MODEL. 121, 122
Alignment, Voltage
Trimmer location

Figure. C - Loudspeaker Wiring

This receiver is a six tube two band A.C. operated Superheterodyne Receiver combining the standard, and short-wave broadcasting bands. The frequency ranges are selected by means of a two position switch. Other features include a double reduction vernier drive using two concentric knobs giving a 10-1 and a 55-1 ratio of speed reduction, a continuously variable tone control, six-inch electrodynamic loudspeaker, automatic volume control, single Pentode output tube and the inherent sensitivity, selectivity, and tone quality of the Superheterodyne.

The chassis is of compact construction, affording unusual accessibility to all parts and adjustments. An "Airplane" type dial calibrated in frequency and showing the location of the short-wave bands is a special feature of this instrument. Figure A shows the schematic circuit, Figure B the wiring diagram and Figure C the loudspeaker wiring.

Line-Up Capacitor Adjustments

In order to properly align this receiver, it is essential that Stock No. 9050 Test Oscillator bo usad. This oscillator covers the frequencies of 150 K.C. to 20.000 K.C. continuously, has good stability and includes an attenuator. In addition to the oscillator, a non-metallic screwdriver such as Stock No. 7065 and an output meter are required. The output meter should be preferably a thermo-couple galvanometer connected across or in place of the cone coil of the loudspeaker.

I.F. Tuning Adjustments - Two transformers comprising three tuned circuits (the secondary of the second transformer is untuned) are used in the intermediate amplifier. These are tuned to 370 K.C. and the adjustment screws are accessible as shown in Figure D. Proceed as follows:

(a) Short-circuit the antenna and ground leads and tune the receiver so that no signal is heard. Set the volume control at maximum and connect a ground to the chassis.

(b) Connect the test oscillator output between the first detector control grid and chassis ground. Connect the output meter across the voice coil of the loudspeaker and adjust the oscillator output so that, with the receiver volume control at maximum, a slight deflection is obtained in the output meter.

(c) Adjust the primary of the second, and the secondary and primary of the first I.F. transformers until a maximum deflection is obtained. Keep the oscillator output at a low value so that only a slight deflection is obtained on the output meter at all times. Go over these adjustments a second time, as there is a slight interlocking of adjustments. This completes the I.F. adjustments.

R.F. and Oscillator Adjustments - The R.F. line-up capacitors are located at the bottom of the coil assemblies instead of their usual position on the gang capacitor. They are all accessible from the bottom of the chassis except the 600 K.C. series capacitor, which is accessible from the rear of the chassis. Proceed as follows:

(a) Connect the output of the oscillator to the antenna and ground leads of the receiver. Check the position of the indicator pointer when the tuning capacitor plates are fully meshed. It should be coincident with the radial line adjacent to the dial reading of 54. Then set the Test Oscillator at 1400 K.C., the dial indicator at 140 and the oscillator output so that a slight deflection will be obtained in the output meter when the volume control is at its maximum position.

(b) With the Range Switch at the "in" position, adjust the three trimmers under the three R.F. coils, designated as L.W. in Figure D, until a maximum deflection is obtained in the output meter. Then shift the Test OScillator frequency to 600 K.c.. The trimmer capacitor, accessible form the rear of the chassis, should now be adjusted for maximum output while rocking the main tuning capacitor back and forth through the signal. Then repeat the 1400 K.C. adjustment.

(c) Now place the Range Switch at the "out" position, shift the Test Oscillator to 15,000 K.C. and set the dial at 150. Adjust the three trimmer capacitors designated as SW in Figure D for maximum output, beginning with the oscillator trimmer. It will be noted that the trimmers will have two positions at which the signal will give maximum output. The position which uses the lower trimmer capacitance, obtained by turning the screw counter-clockwise, is the proper adjustment for the oscillator. The position that uses a maximum capacitance is correct for the detector and R.F. In conjunction with the detector adjustment, it is advisable to rock the main tuning capacitor back and forth while making the adjustment. This completes the line-up adjustments.

The important points to remember are the need for using the minimum oscillator output to obtain a deflection in the output meter with the volume control at its maximum position and the manner of obtaining the proper high frequency oscillator adjustment

Power Transformer Connections

The power transformer used in this Model has a tapped primary winding. The transformer is normally connected for lines ranging in voltage from 110 to 125 volts. If for any reason the line is normally below 110 volts the connections should be changed so the tap will be used. This is done by unsoldering the black with red tracer transformer lead connected to the power switch (on tone control) and substituting the red and black lead normally taped up. The black with red tracer lead should then be carefully taped to prevent short-circuit.

Figure D - Location of Line-Up Capacitors

RADIOTRON SOCKET VOLTAGES
115 Volts, A.C. Line - No Signal

Page 3:

Model 121, 122 Schematic

RCA-VICTOR CO., INC.

Electrical Specifications
Voltage Rating ... 100 - 125 Volts
Frequency Rating ... 25 - 60 and 50 - 60 cycle
Power Consumption ... 60 Cycle, 75 Watts; 25 Cycle, 80 Watts
Number and Type of Radiotrons ... 2 RCA-58, 1 RCA-2A7, 1 RCA-2B7, 1 RCA-2A5, 1 RCA-80 - Total 6
Tuning Ranges ... 540 K.C. - 1,500 K.C. - 5,400 K.C. - 15,350 K.C.
Undistorted Output ... 1.75 Watts

Figure A - Schematic Diagram

Page 4:

MODEL 121,122 Chassis wiring

Figure B - Wiring Diagram

Page 5:

REPLACEMENT PARTS Insist on genuine factory tested parts, which are readily identified and may be purchased from authorized dealers