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General Electric Model HJ-1205 Radio Service Data Sheet
June 1940 Radio-Craft

June 1940 Radio-Craft

June 1940 Radio Craft Cover - RF Cafe[Table of Contents]

People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.

This Radio Service Data Sheet for the General Electric Model HJ-1205 floor console model vacuum tube radio came from the June 1940 edition of Radio-Craft magazine, published by Hugo Gernsback. I post these for the sake of hobbyists and historians searching for information on vintage electronics. If you happen to own one of these radios, whether in its restored or unrestored condition, please send me a photo and I will be glad to post it here with attribution to you.

General Electric Model HJ-1205 Radio Service Data Sheet

General Electric Model HJ-1205 Radio Service Data Sheet, June 1940 Radio-Craft - RF Cafe12-Tube Superheterodyne; A.C. Operation; 3 Bands (540-1,600 kc., 2,300-7,000 kc., 7,000-22,000 kc.); Power Output (undistorted). 8.5 W.; A.V.C.; Tone Monitor; "Eye" Tube; Built-in, Rotatable "Beam-a-Scope" Antenna; Dual P.M. Dynamic Speakers, 1 - 12 in. and 1 - 6 1/2 in.; 11 Push buttons (Keys), including keys for Phono, or Television Audio Channel.

The model HJ-1205 is a 3-band A.C. operated receiver employing 12 General Electric pre-tested tubes in a superheterodyne circuit. The receiver is equipped with 11 feathertouch tuning keys, 8 of which may be set up for favorite stations. The 3 remaining keys allow power control, manual tuning and phonograph or television audio reception. Each model is also equipped with the new Super Beam-a-scope; a highly efficient, self-contained antenna circuit. Other features of design include: dual dynapower speakers (See "The Use of Dual Loudspeakers," in this issue of Radio-Craft.), floodlighted station-key finder, visual dial, iron-core I.F. transformers, automatic tone compensation, automatic volume control, and push-pull output.

Super Beam-a-Scope

The Super Beam-a-scope is essentially a tuned coil antenna wound on a frame and shielded by a Faraday screen against electrostatic disturbances. This construction favors the desired signal over a local man-made noise source in 3 ways. First, since any noise source is composed of 2 components - electrostatic and electromagnetic fields - the Super Beam-a-scope may be revolved so that a null point is found where no voltage is produced from these 2 components. Due to the fact that this null point is very sharp, it is very unusual that any desired station will be in a direct line with the rejected noise signal and thereby have its signal strength reduced appreciably.

In the second place, the Super Beam-a-scope eliminates the external return path to ground present in the case of an unshielded antenna. This reduces or eliminates local man-made noise sources in much the same way as a shielded antenna lead-in does in an ordinary antenna installation.

In the third place the Super Beam-a-scope discriminates against the electrostatic component of an incoming wave in comparison with the electromagnetic component, because of the Faraday shield. Since the electrostatic component of a local noise source is a great deal larger than the electromagnetic component, this rejection property brings about an enormous increase in signal-to-noise ratio.

The above operation is only available on the broadcast band and in this position the Super Beam-a-scope is also the 1st tuned grid circuit. On the "C" and "D" bands, the Super Beam-a-scope is grounded at the grid end thus preventing absorption spots due to loop resonance. (See "How the Beam-a-scope Works," Radio-Craft, April 1939.)

Fig. 1. Location of trimmers and, Fig. 3, circuit of I.R.E. dummy antenna.

G.E. model HJ-1205 dual-loudspeaker receiver.

Loudspeakers

The voice coils are accurately and permanently centered at the factory and should seldom give trouble. In case a voice coil needs recentering it will be necessary to replace the entire cone and voice coil assembly.

Note: In no case should the magnet be removed from the assembled position without remagnetizing after replacing it.

Special Service Data

The following information will be found very useful in servicing receivers if a vacuum-tube voltmeter or similar voltage measuring instrument is available.

(1) Stage Gains‡

(a) Antenna post to converter grid Band "B" (Beam-a-scope connected) *-3 V. at 1,000 kc.

Band "C" (Beam-a-scope disconnected) **-3 V. at 4 mc.

Band "D" (Beam-a-scope disconnected) **-3 V. at 18 mc.

(b) Converter grid to 1st 6SK7 grid, 30 at 455 kc.

(c) 1st 6SK7 grid to 2nd 6SK7 grid, 6 at 455 kc.

(d) 2nd 6SK7 grid to 6H6 det. plate, 70 at 455 kc.

(2) A 400-cycle signal of 0.04-V. across volume control will give 1/2-W. speaker output.‡ (Volume Control turned to maximum)

(3) Average D.C. voltage developed across oscillator grid resistor (R1) with gang closed.

Band "B" .......... 6.5 V.

Band "C" .......... 7 V.

Band "D" .......... 2.8 V.

‡Variations of +10%, -20% permissible.

*Use I.R.E. dummy antenna.

**Use 70 mmf. condenser between signal generator and antenna post.

Fig. 2. I.F. curves. A, sharp position; B, expanded position.

Alignment Procedure

The alignment procedure is given in table form. Use the designated "dummy" antenna in making each Individual alignment. The I.F. alignment may be performed with the chassis removed from the cabinet and the Beam-a-scope disconnected. The R.F. alignment on "C" and "D" bands should be performed with the Beam-a-scope disconnected and a 70 mmf. mica condenser between the signal generator and the point of Input. The R.F. alignment on "B" band should be performed with the chassis and Beam-a-scope mounted in the cabinet and properly connected.

I.F. Alignment with Oscilloscope*

I.F. Alignment with Output Meter*

R.F. Alignment

*Use "dummy" antenna consisting of 0.05-mf. condenser between signal generator and point of input.

** Use a "dummy" antenna consisting of 70 mmf. condenser between signal generator and point of input with "Beam-a-scope" disconnected.

*** Use an I.R.E. "dummy" antenna as shown in Fig. 3 between signal generator and the point of input.

Fig. 4. Normal socket voltages.

 

Condensers

C1 Tuning

C3 "C" Band ant. trimmer

C4 "D" Band ant. trimmer

C5"B" Band osc. trimmer

C6 "C" Band osc. trimmer

C7 "D" Hand osc. trimmer

C8 "B" Band padder

C9 0.0016-mf. mica

C10 0.0043-mf. mica

C11 750 mmf. silvered mica

C12 150 mmf. mica

C13 0.1-mf. paper

C14 47 mmf. mica

C15 01.-mf. paper

C18 47 mmf. mica

C19 0.05-mf. paper

C23 0.05-mf. paper

C24 100 mmf. mica

C25 41 mmf. mira

C26 0.01-mf. paper

C27 470 mmf. mica

C28 0.01-mf. paper

C29 0.05-mf. paper

C31 0.01-mf paper

C32 0.003-mf. paper

C34 47 mmf. mica

C35 0.05-mf paper

C36 0.05-mf. paper

Q37a 20 mf. 25 V. dry elec.

C37b 20 mf. 300 V. dry elec.

C37c 20 mf. 300 V. dry elec.

C37d 40 mf. 350 V. dry elec.

C38 0.01-mf. 1,000 V. paper

C42 0.01-mf. 1,000 V. paper

C43 7-65 mmf. ant. trimmer

C44 7-65 mmf. ant. trimmer

C45 20-180 mmf. ant. trimmer

C46 20-180 mmf. ant. trimmer

C47 20-180 mmf. ant. trimmer

C48 100-490 mmf. ant.trimmer

C49 100-490 mmf. ant.trimmer

C50 100-490 mmf. ant.trimmer

C51 0.1-mf. paper

C54 0.05-mf. paper

Coils

L1 Beam-a-scope

L2 "C" Band ant. coil

L3 "D" Band ant. coil

L4 "B" Band osc. coil

L5 "C" Band ant. coil

L6 "D" Band ant. coil

L7, 8 Tuning coils (no code)

L9, 10, 11 Tuning coils (code-red)

L12, 13, 14 Tuning coils (code-blue)

Resistors

R1 22.000 ohms, carbon

R2 1. meg. carbon

R3 6,800 ohms, carbon

R4 47,000 ohms, carbon

R5 330 ohms, carbon

R7 1,000 ohms, carbon

R8 47,000 ohms, carbon

R9 0.22-meg. carbon

R10 47,00 ohms,carbon

R1 2.2-megs., carbon

R12 470 ohms, carbon

R13 2 megs. vol. con.

R14 0.15-meg., carbon

R15 3,300 ohms, carbon

R16 47,000 ohms, carbon

R17 0.15-meg., carbon

R18 47,000 ohms, carbon

R19 3,300 ohms, carbon

R20 1.5-megs., carbon

R21 0.27-meg., carbon

R22 0.22-meg., carbon

R23 0.22-meg., carbon

R24 100 ohms. 3.4 W. wire-wound

R25 2,400 ohms, or 3,300 ohms 2 w. carbon

R26 2.200 ohms, 2.6 W. wire-wound

R27 56 ohms, carbon

R28 100 ohms, carbon

R29 47,000 ohms, carbon

R30 1 meg., carbon

R32 5.6 megs., carbon

R3 1,000 ohms, carbon

R34 1,000 ohms, carbon

R40 33 ohms, carbon

R41 4.7 megs., carbon

R43 0.2-meg., carbon

R44 0.15-meg. carbon

R45 2,200 ohms carbon

P1, 2 Pilot lights, Mazda No. 44

S1 Ant. band switch

S2 Osc. band switch

S3 Tone switch

S4 Phono switch

S5 Power switch

S6 Manual switch

S7 Ant. section touch tuning switch

S8 Osc. section touch tuning switch

 

Radio Service Data Sheets

These schematics, tuning instructions, and other data are reproduced from my collection of vintage radio and electronics magazines. As back in the era, similar schematic and service info was available for purchase from sources such as SAMS Photofacts, but these printings were a no-cost bonus for readers.

 

 

 

Posted April 28, 2015

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