RCA Mfg. Co., Inc.

IF Peak 460 KC

Internal Connections of Power Transformer
Figure 5 - Universal Transformer Connections

RCA Mfg. Co., Inc.

Models 128E, 224E
Chassis Wiring

Figure 2 - Chassis Wiring Diagram

RCA Mfg. Co., Inc.

Models 128E, 224E
Trimmers, Socket
Voltage, Speakers

Figure 3 - Table Loudspeaker Wiring

Figure 4 - Console Loudspeaker Wiring

Figure 7 - Tube Socket Voltages
All Voltages are to Ground

RCA Mfg. Co., Inc.

Models 128E, 224E
Alignment, Voltage

Checking with Tuning Wand

Before making any R.F., oscillator or first detector adjustments, the accuracy of the present adjustments may be checked by means of the tuning wand (Stock No. 6679). The tuning wand consists of a bakelite rod having a brass cylinder at one end and a special finely divided iron insert at the other end. Inserting the cylinder into the center of a coil lowers its inductance, while inserting the iron end increases its inductance. From this, it is seen that unless the trimmer adjustment for a particular coil is perfect at alignment frequencies, inserting one end of the wand may increase the output of a particular signal. A perfect adjustment is evidenced by a lowing of output when either end of the wand is inserted into a coil.

The shields over the R.F. coil assembly have a hole at their top for entrance of the tuning wand. The location of the various coils inside of the shield is shown in Figure 8. An example of the proper manner of using the tuning wand would be to assume the external oscillator were set at 1720 and the signal tuned in, and the output indicator should be connected across the voice coil of the loudspeaker. Then the tuning wand would be inserted, first one end and then the other end, into the top of the three transformers at the left of the R.F. assembly, facing the front of the chassis. A perfect adjustment of the trimmer would be evidenced by a reduction in output when each end of the wand is inserted in each of the three transformers. if one end - for example, the iron end - when inserted in one coil caused an increase in output, then that circuit is low. An increase in the trimmer capacitance would be the proper remedy.

(2) I.F. Tuning Capacitor Adjustments

The receiver has one I.F. stage that employs two transformers in conjunction with four adjustable capacitors. These capacitors may require adjustment, being tuned to 460 K.C.

A detailed procedure for making this adjustment follows:
(a) Connect the output of an external oscillator tuned to 460 K.C. between the first detector grid and ground. Connect the output indicator across the voice coil of the loudspeaker.
(b) Place the oscillator in operation at 460 K.C. Place the receiver in operation and adjust the station selector until a point is reached (Band B) where no signals are heard and turn the volume control to its maximum position. Reduce the oscillator input until a slight indication is obtained in the output indicator.
(c) Refer to Figure 6. Adjust each trimmer of the I.F. transformers until a maximum output is obtained. Go over the adjustments a second time.

(3) R.F., Oscillator and First Detector Adjustments

Four R.F., oscillator and first detector adjustments are required in Bands "A" and "B". Three are required in Band "C".

To properly align the various bands, each band must be aligned individually in the order given. This is "A", "B", and "C". The preliminary set-up requires the external oscillator to be connected between the antenna and ground terminals of the receiver and the output indicator must be connected across the voice coil of the loudspeaker. The volume control must be at its maximum position and the input from the oscillator must be at the minimum value possible to get an output indication under these conditions. in the high frequency bands, it may be necessary to disconnect the oscillator from the receiver and place it at a distance in order to get a sufficiently low input to the receiver.

The dial pointer must be properly set before starting any actual adjustments. This is done by turning the variable capacitor until it is at its maximum capacity position. One end of the pointer should point exactly at the horizontal line at the lowest frequency end of Band "A", while the other end should point to within 1/24 inch of the horizontal line at the highest frequency and of Band "A".

Figure 8 - Location of Coils in Shields

Figure 6 shows the location of the trimmers for each band. Care must be exercised to merely adjust the trimmers of the band under test.

Band "A"
(a) Set the Band Switch at "A."
(b) Tune the external oscillator to 410 K.C., set the dial pointer at 410 K.C. and adjust the oscillator detector and R.F. trimmers for maximum output.
(c) Shift the external oscillator frequency to 175 K.C. Tune in the 175 K.C. signal irrespective of scale calibration and adjust the series trimmer, marked 175 K.C. on Figure 6, for maximum output, at the same time rocking the variable tuning capacitor. Then readjust at 410 K.C. as described in (b).

Band "B"
(a) Set the Band Switch at "B."
(b) Tune the external oscillator to 1720 K.c., set the pointer and 1720 K.C. and adjust the oscillator, detector and R.F. trimmers for maximum output.
(c) Shift the external oscillator frequency to 600 K.C. Tune in the 600 K.C. signal, irrespective of scale calibration, and adjust the series trimmers, located on rear apron of chassis, for maximum output, at the same time rocking the variable tuning capacitor. Then readjust at 1720 K.C. as described in (b).

Band "C"
(a) Set the Band Switch at "C."
(b) Tune the external oscillator to 17,000 K.C., set the pointer at 18 M.C. Adjust the oscillator trimmer for maximum output. The trimmer should be set at the first peak obtained when increasing the trimmer capacitor from minimum to maximum.
(c) Check for the image signal, which should be received at approximately 17,080 K.C. on the dial. It may be necessary to increase the external oscillator output for this check.
(d) Reduce the capacity of the detector trimmer, while rocking the tuning capacitor, until the signal disappears. The first detector circuit is then aligned with the oscillator circuit and the RCA 6A7 tube is blocked. Then increase the capacity of the detector trimmer, while rocking the tuning capacitor, until the signal is peaked for maximum output.
(e) The antenna trimmer should now be peaked for maximum output. It is not necessary to rock the main tuning capacitor while making this adjustment.

(4) Power Transformer Connections

The 220-volt power transformer furnished with some instruments includes taps for operating on 110-volt lines. Figure 5 shows the schematic circuit of the transformer and the proper voltage to be applied to the various taps. The taps are located on the power transformer assembly and are accessible without removing the chassis from the cabinet.

(5) Voltage Readings

The following voltages are those at the various tube sockets while the receiver is in operating condition. No allowance has been made for currents drawn by the meter, and if low-resistance meters are used, such allowances must be made:

Radiotron Socket voltages
115-Volt A.C. Line - No Signal - Volume Control Maximum

Radiotron Number	Cathode to Ground, Volts, D.C.	Screen Grid to Ground, Volts, D.C.	Plate to Ground, Volts, D.C.	Plate Current, M.A.	Heater Volts
RCA 6D6 - R.F.	6.0	105	265	9.0	6.3
RCA 6A7 Det.	6.0	105	265	3.5	6.3
RCA 6A7 Osc.	-	-	220	4.5	6.3
RCA 6D6 - I.F.	6.0	105	265	9.0	6.3
RCA 6B7 - 2nd Detector	3.0	50	90*	0.7	6.3
RCA 41 - Power	16.5	26.5	245	30.0	6.3
RCA 80 - Rectifier	-	-	690 (RMS)	70.0	5.0

*Voltage calculated from 265 V. + B

RCA Mfg. Co., Inc.

Models 128E, 224E
Parts List

Receiver Assemblies
4427 - Bracket, Volume control or tone control mounting bracket
2747 - Capacitor - contact cap - Package of 5
3861 - Capacitor - adjustable trimmer capacitor (C2)
4442 - Capacitor - 50 mmfd. (C47)
4662 - Capacitor - 80 mmfd. (C37)
4413 - Capacitor - 360 mmfd. (C21)
4634 - Capacitor - 1120 mmfd. (C50)
4515 - Capacitor - 1160 mmfd. (C34)
4670 - Capacitor - 2250 mmfd. (C15)
4523 - Capacitor - 2400 mmfd. (C17)
4524 - Capacitor - 2850 mmfd. (C25)
4435 - Capacitor - 0.02 mfd. (C39)
4518 - Capacitor - 0.05 mfd. (C35)
4417 - Capacitor - 0.05 mfd. (C4, C12, C29)
3877 - Capacitor - 0.1 mfd. (C40)
4415 - Capacitor - 0.1 mfd. (C6, C15, C30)
4645 - Capacitor - 0.1 mfd. (C7, C26)
3597 - Capacitor - 0.25 mfd. (C38, C45)
4525 - Capacitor - 4.0 mfd. (C36)
4428 - Capacitor - 8.0 mfd. (C44)
7790 - Capacitor - 10.0 mfd. (C43)
4692 - Capacitor pack - Comprising one 0.035 mfd. and one 0.005 mfd. capacitors (C41, C42)
7589 - Capacitor pack - Comprising two 4.0 mfd. capacitors (C16, C46)
4358 - Clamp - Electrolytic capacitor mounting clamp
4734 - Coil - Antenna coil "A" (L26, L27, C51)
7803 - Coil - Antenna coil "B & C" (L1, L2, L5, L6, C1, C3)
4751 - Coil - Detector coil "A" (L28, L29, C52)
7805 - Coil - Detector coil "B & C" (L7, L8, L11, L12, C8, C9, C11)
7807 - Coil - Oscillator coil "B & C" (L13, L14, L17, L18, C19, C24)
4733 - Coil - Oscillator coil "A" (L30, L31, C53)
7801 - Condenser - 3-gang variable tuning condenser (C5, C13, C18)
4340 - Lamp - Dial lamp - Package of 5
3632 - Resistor - 500 ohms - Carbon type - 1 watt (R24) - Package of 5
3218 - Resistor - 600 ohms - Carbon type - 1/4 watt (R2, R6, R8) - Package of 5
4370 - Resistor - 1000 ohms - Carbon type - 1/4 watt (R3, R7) - Package of 5
3997 - Resistor - 4000 ohms - Carbon type - 1/4 watt (R14) - Package of 5
6318 - Resistor - 10,000 ohms (R21)
3114 - Resistor - 50,000 ohms - Carbon type - 1/4 watt (R16, R18) - Package of 5
3602 - Resistor - 60,000 ohms - Carbon type - 1/4 watt (R5) - Package of 5
3118 - Resistor - 100,000 ohms - Carbon type - 1/4 watt (R1, R4) - Package of 5
3116 - Resistor - 200,000 ohms - Carbon type - 1/4 watt (R15) - Package of 5
6186 - Resistor - 500,000 ohms - Carbon type - 1/4 watt (R17) - Package of 5
3033 - Resistor - 1 megohm - Carbon type - 1/4 watt (R10) - Package of 5
6242 - Resistor - 2 megohms - Carbon type - 1/4 watt (R11, R13) - Package of 5
3413 - Resistor - 5,000 ohms - Carbon type - 1/4 watt (R22, R23) - Package of 5
4513 - Resistor - 30,000 ohms - Carbon type - 1/4 watt (R20) - Package of 5
4521 - Shield - Antenna R.F. or oscillator coil shield
4145 - Shield - First detector or output Radiotron shield
4103 - Shield - I.F. amplifier Radiotron shield
6955 - Shield - R.F. amplifier Radiotron shield
3782 - Shield - Second detector Radiotron shield
3529 - Socket - Dial lamp socket
3859 - Socket - 4-contact Radiotron socket
6676 - Socket - 6-contact output Radiotron socket
7485 - Socket - 6-contact Radiotron socket
3572 - Socket - 7-contact Radiotron socket
4379 - Strip - Antenna terminal engraved "ANT-GND"
4684 - Switch - Operating switch (S11)
4728 - Switch - Range switch (S1, S2, S3, S4, S5, S6, S7, S8, S9, S10)
4517 - Tone control (R19)
4431 - Transformer - First intermediate frequency transformer (L19, L20, C27, C28, C48)
4433 - Transformer - Second intermediate frequency transformer (L21, L22, C31, C32, C33, R9)
9511 - Transformer - Power transformer - 105-125 volts - 50-60 cycles (T1)
9512 - Transformer - Power transformer - 105-125 volts - 25-40 cycles
9513 - Transformer - Power transformer - 105-250 volts - 40-60 cycles
4519 - Volume control (R12)

Drive Assemblies

4362 - Arm - Band indicator operating arm
10194 - Ball - Steel ball for condenser drive assembly - Package of 20
4422 - Clutch - Clutch drive assembly for variable condenser drive
4510 - Drive - Tuning condenser drive assembly
4361 - Indicator - Band indicator (celluloid)
4732 - Scale - Station selector dial scale
3943 - Screen - Dial light screen (celluloid) - Package of 2
3993 - Screw - Number 6-32-5/32 square head set screws for band indicator operating arm - Package of 10
4669 - Screw - Number 8-32-5/32 set screw for variable condenser drive assembly - Package of 10
4377 - Spring - Band indicator and arm tension spring - Package of 5
4378 - Stud - Band indicator operating arm stud - Package of 5

Reproducer Assembly Table Model

4526 - Cable - 3-conductor - Reproducer cable
7818 - Reproducer complete

Reproducer Assembly Consol Model

4473 - Board - Terminal board assembly
9460 - Coil - Field coil, magnet and cone support (L24)
8935 - Cone - Reproducer cone (L23) - Package of 5
9527 - Reproducer - Complete
4472 - Transformer - Output transformer (T2)

Miscellaneous Assembly

4677 - Bezel - Station selector dial (escutcheon) bezel
6614 - Glass - Station selector dial glass
4520 - Indicator - Station selector indicator pointer
4449 - Knob - Station selector, volume control, tone control, range switch or operating switch knob - Package of 5
4678 - Ring - Dial glass retaining ring - Package of 5
4527 - Screw - Chassis mounting screw assembly comprising 4 spacers, 4 screws, 4 lock-washers, 4 washers, 8 cushions - For table model
4685 - Screw - Chassis mounting screw assembly - Comprising 4 spacers, 4 screws, 4 lock-washers, 4 washers and 8 cushions - For console model
4632 - Screw - Number 8-32-7/16 headless set screw for knobs - Package of 10