RCA MFG., CO., INC.

MODEL 103 Schematic Voltage

Figure 5 - Loudspeaker Wiring

IF PEAK 460 KC.

RADIOTRON SOCKET VOLTAGES - BETWEEN ELEMENTS
120. Volt. 60 - Cycle Line - Maximum Volume Control Settings - No Signal

R.C.A. - VICTOR CO., Inc.
Radiola Division

RCA Loudspeaker Model 100A

R.C.A 100B and 103 Speakers

104 Loudspeaker

RCA MFG. CO., INC.

MODEL 103 Chassis Wiring

Figure 2 - Chassis Wiring Diagram

RCA MFG. CO., INC.

MODEL 103 Circuit Data, Socket Trimmers, Voltage Alignment Parts

DESCRIPTION OF ELECTRICAL CIRCUIT

The first stage is a combined detector and oscillator using an RCA Radiotron 6A7. The two functions are obtained through means of individual tuned circuits. On the detector tuning coil a tap is made, so that a portion of the coil can be short-circuited by switch contacts and thus extend the tuning of the receiver to the higher frequency range. The oscillator second harmonic is used to produce the intermediate frequency for the upper tuning range. The oscillator circuit is arranged to have the low-frequency trimmer capacitor attached in series with the inductance, permitting accuracy in its adjustment to be easily secured, and to give a more uniform sensitivity over the tuning range.
In the following stage, the I.F. amplification and final detection take place in the dual-purpose RCA 6F7.

The input section of this tube constitutes a sreen-grid I.F. amplifier, with the output elements arranged to perform as a triode detector.
One RCA - 41, a Pencode type, is employed in the audio output stage.
The rectifying unit consists of an RCA - 1-V, a cathode-type, half-wave tube. Its high voltage is supplied from the power transformer secondary, which is a single winding capped at various points for furnishing heater current to all Radiotrons of the receiver. The heater of the RCA - 41 stage and the pilot lamp are supplied by one section of the secondary winding: and the remaining three heaters are connected series to receive supply from a 19 - volt section of the same winding.

Voltage Rating ... 105-125 volts
Frequency Ratings ... 25-60 or 50-60 Cycles
Power Consumption ... 40 watts at 115 volts
Number and Type of Radiotrons ... 1 RCA-6A7, 1 RCA-6F7, 1 RCA-41, 1 RCA-1V -> total 4
Tuning Frequency Ranges ... 540-1500 K.C. and 1600-3500 K.C.
Intermediate Frequency ... 490 K.C.
Maximum Undistorted Output ... 1.9 watts
Maximum Output ... 3 watts
Line-up Frequencies ... 460 K.C., 600 K.C., and 1400 K.C.

SERVICE DATA

(1) ALIGNMENT PROCEDURE
Locations of the alignment condensers are indicated on Figure 3. There are five adjustments necessary. Before attempting to align the receiver, the antenna must be disconnected to obviate any interference that may be caused by pickup on a local station. The adjusting should then be performed in order as follows:
(a) First I.F. Transformer - Connect the output of an external oscillator, which is set to produce a 460 KC. signal, from the RCA - 6A7 detector grid to chassis-ground. Tune the primary and secondary trimmers C-11 and C-12, respectively, for maximum receiver output.
(b) Receiver Oscillator and Detector - Two adjustments are provided. The first is accomplished by feeding a 1400 KC. signal from an external oscillator into the antenna-ground terminals. Set the tuning dial at 1400, and adjust the two trimmers of the tuning condenser for maximum receiver output. For the second oscillator adjustment, a signal of 600 KC. is required from the external source, fed into the antenna-ground connections. The trimmer for this frequency appears on the rear of the chassis. Adjust this trimmer, simultaneously rocking the tuning condenser through the signal, until maximum receiver output is obtained. Reading of the dial should fall within reasonable limits of accuracy at the 600 KC point.

(2) VOLTAGE READINGS
In Figure 3, voltage values from tube contacts to ground are shown. They are the actual operating values and should be checked with the tubes in place. The table of Figure 4 lists the operating voltages and currents, referred to cathode, and measurable by means of a socket adaptor or set analyzer.

Figure 3 - Line-Up Capacitor Locations and Miscellaneous Voltages at Radiotron Sockets, 120-Volt 60-Cycle Line - Volume Control at Maximum - No Signal

REPLACEMENT PARTS