Zenith Models 430 and 440 12-Tube Superheterodyne
Radio Service Data Sheet
February 1933 Radio-Craft

February 1933 Radio-Craft [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

In a continuing effort to provide archival material for researchers and for anyone seeking information on a particular radio restoration project, this Radio Service Data Sheet for the Zenith Model 430/440 radio from a 1933 edition of Radio-Craft is being posted. An Internet search will show that there are many people engaging in such activities. Restoring my Crosley Model 03BC console radio would have been more difficult if not for others who have done similar work to assist the 'community.' I generally despise the phrase "giving back" because it is usually uttered by people that really owe nothing to anyone, but somehow feel obligated to do so or are conditioned to automatically say such things. This is a case where I benefitted from somebody else's work and there is an opportunity to return the favor.

Update: Mr. Steve  of The Radio Fox website wrote to express thanks for having this information posted. He owns both a Zenith Model 430 and a Zenith Model 440 (click thumbnails).

Zenith Models 430 and 440 12-Tube Superheterodyne Radio Service Data Sheet

(Dual reproducers, Zenith class AAA A.F. power amplifier; illuminated auto type full-vision control escutcheons; 540 to 1750 kc. - 121 channels, including police band; silent tuning; A.V.C.; low-volume tone compensator; "shadowgraph" tuning; tone control; 110 V. or 220 V. line.)

The newest product of Zenith Radio Corp. is the model 430 receiver; equipped with the Zenith automatic tuning device, it is the model 440. The outstanding feature of this set is the "class AAA" system of A.F. amplification used;

Line potential, 115 V.; all controls maximum.

All tube readings, except heaters, are socket to ground, using 1,000-ohms-per-volt D. C. meter.

Resistor R1, manual volume control. 0.5-meg., total, tapped at 0.4-meg. from ground end; R2, tone control, 0.5-meg.; R3, quiet-tuning control, 400 ohms; R4, R6, R10, 1,900 ohms; R5, 150 ohms; R7, R25, 1,500 ohms; R8, R17, 0.25-meg.; R9, R16, 24,000 ohms; R11, R12, 50,000 ohms; R13, 0.1-meg.; R14, R18, 500 ohms; R15, 8,000 ohms; R19, R20, 1 meg, ; R21, 2,500 ohms; R22, 18,000 ohms; R23, R24, 400 ohms.

Condensers C1, C2, C3, tuning gang; C1A, C2A, C3A, tuning trimmers; C4 to C7, I. F. trimmers; C8, L. F. padder; C9, H. F. coupling condenser; C10, C11, C12, 0.2-mf.; C13, 0.1-mf.; C14, C15, C16, C17, C19, C20, C24 (25 cycles, 0.4-mf.), C30, C31, C35, .1-mf.; C18, 0.05-mf.; C21, C22, C23, C25, C26, C27, 8 mf.; C28, 0.5-mf.; C29, 25 mmf.; C32, C33, 500 mmf.; C34, 0.002-mf.

The condenser gang in this receiver is aligned at 1,500 kc.; the oscillator padder is aligned at 600 kc.

Field coil No. 1 has a resistance of 1,600 ohms; field coil No. 2 has a resistance of 2,000 ohms for section A and 3,500 ohms for section B. Choke Ch.2 has a resistance of 400 ohms.

There are no circuit changes or switches in this receiver for the reception of police calls. The tuning dial, itself, actually takes in the police frequencies since it covers a total range of 540 to 1,750 kc.

"Shadowgraph" tuning is effected by means of a vane fastened to a meter movement connected in the plate-supply circuit to tubes V1, V2, V3. The incoming signal causes this "meter" to move in the usual manner, thus twisting the vane so that it either obstructs the light and casts a wide shadow (off resonance), or permits the light to pass, casting a shadow no wider than the thickness of the vane (exact resonance of the tuned circuits).

Class AAA A.F. amplifier is the Zenith designation for a system employing three power tubes, each of which are biased as class A amplifiers, one of which is used to drive the other two in push-pull. If the grids were overdriven with the usual type of coupling transformer, having a high secondary impedance, between the driver and the output tubes and the push-pull grids overdriven, extreme distortion would take place. This difficulty is overcome by employing a special transformer of step-down ratio having larger wire and much less resistance in its secondary. This transformer is a very important part of the system. With such an arrangement it is possible to drive the grids of the power tubes positive without introducing distortion, because of the driver being a power tube and capable of supplying the necessary current on such peaks. The primary of this transformer has a higher impedance than is normally used, which value is somewhat reduced as the impedance changes in the secondary, when the power grids are driven positive. Its impedance, however, at the lowest value, still matches the driver plate circuit. It should be remembered that in an ordinary class A amplifier distortion enters when the grids are driven positive by virtue of the previous tube not supplying sufficient power for grid excitation of the output tubes. In other words, in class A, voltage on the power grids is available as long as they do not go positive. As soon as they are driven past zero in that direction the previous amplifier can no longer supply the necessary power.

Above, Arrangement of the tubes in the "430." Right, Comparative figures indicating the effectiveness of A.F. amplifiers classes A, push-pull; B, push-push; pentodes in push-pull, and AAA, push-pull, Watts rating, respectively, 4.3 W., 0.8- to 24 W., 6.3 W., 14.2 W.

Summing up the above, the triple A amplifier is a combination of both class A and class B. The exception being that the tubes are biased as class A, but by virtue of the power delivered by the driver and the special coupling transformer, sufficient power is supplied for the power tube to draw grid current and still prevent distortion as in the class B amplifier.

Many set analyzers will not accommodate the new tubes, consequently, all voltage readings are to ground. Thus, for instance. the actual voltage on the plates of the power tubes is 295 V.

The two reproducers are similar in construction but one is peaked at 90 cycles and the other at 70 cycles. (This is done to cancel the natural period of each reproducer.) The paralleled voice coils result in four times the power obtainable from a single reproducer, states the manufacturer.

An overall sensitivity of less than one-half microvolt-per-meter is obtained with an undistorted power output of 15 watts. The total line consumption at 115 V. is 125 W.

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. There are 220 Radio Service Data Sheets as of February 2, 2018.

Remler Model No. 36 Dual-Wave Auto-Radio Stromberg-Carlson No. 82 All-Wave Receiver Majestic A.V.C. Model 290 Chassis FADA 9 Tube Model 190 "Metal" All-Wave RCA Victor Models 9T and K2 9-Tube, 5- to 566-Meter Motorola "Golden Voice" Model RCA Victor Model H-6 Simplex Model TA Automatic "Magic Eye" Model A1 Silvertone Models 4488 and 4588 (Chassis No.101412) and 4488A and 4588A (Chassis No. 101412A) RCA Victor Model M109 "De Luxe" 7-Tube Auto-Radio Receiver Crosley Model 6625 6-Tube 3-Band Receiver International Model 77 Series 7-Tube Dual-Band Receiver Belmont Model 6D121 General Electric Models 60, 62 Admiral Model 7C64 Radiola "28" Super and "104" Power Speaker Sonora Model TW-49 Stromberg-Carlson Models 1020, 1120, Series 10 Air King Model 4604D Sparton Models 526, 526X, 526PS Truetone Model D2624 Admiral Models 6EI, 6EIN Detrola Models 571A, 571B General Electric Model 250 Howard Model 920 Colonial Model 652 5-Tube Broadcast-Short-Wave Fairbanks-Morse 9-Tube All-Wave Model 91 International Model 500 5-Tube Dual-Range Battery Emerson Model 678 "Auto-Dynamic" 5 Tube Stromberg-Carlson Nos. 230 and 231 Series Atwater Kent Model 649 All-Wave Howard Model G-26, and "Airplane 4" Model AA25 Montgomery Ward "Airline" Series 7GM 7-Tube High-Fidelity Receiver RCA Victor Model T5-2 5-Tube, 2-Band A.C. Superheterodyne Receiver Majestic "Models 50," "51" and "52" Bremer-Tully Model 7-70 and 7-71 General Electric Model M-49 4-Tube Radio-Phonograph Dual-Wave Superheterodyne RCA-Victor Radiola "Superette" Model R7 Superheterodyne Crosley Model AC-7 and AC-7C Westinghouse "Columnaire" Models WR-8 and WR-8-R (Remote Control) Characteristics of Metal Tubes - and Other "Octal" (8-Prong) Base Types Kolster K20, K22, K25, K27 and K37 Six-Tube Receivers Stromberg-Carlson Nos. 62 and 63, 8-Tube High-Fidelity Chassis RCA Model 103, 4-Tube A.C. Compact Dual-Wave FADA "Special" Model 265-A and FADA "7" Model 475-A General Electric Model C-62 6-Tube Battery Emerson 5A Automotive Zenith 666 Automotive Motorola 100 Automotive Crosley Roamio 4-A-1 Automotive American-Bosch 524A Automotive Crosley Model 1316 (in Model 167 Console) RCA Victor "High-Fidelity Electrola," Model R-99 AMRAD Model 81 ("Bel Canto" Series) Receiver Fada 103 Fadalette, Stewart-Warner Series 108, DeWald 54 Dynette Sets RCA Victor R-27 and Philco 53 Ultra-Midget A.C.-D.C. Radio Receivers Majestic Models Fairfax and Sheffield 8-Tube Stromberg-Carlson No. 29, 9-Tube Superhet International Kadette Model 400 4-Tube Battery-Operated Superhet RCA Victor Model 5M 5-Tube Auto Superhet Majestic Model 11 Short-Wave Converter Silver-Marshall Model 727-DC Battery-Operated Superheterodyne RCA Victor Model VHR-307 Home Recording - Phono-Radio Combination Delco 32-Volt Radio Receiver Chassis Models RA-3, RB-3 and RC-3 Majestic Chassis Models 380 A.C. T.R.F., and 400 A.C.-D.C. Superheterodyne General Motors S1A, S1B Admiral Model 7C63, Chassis 7C1 Westinghouse Model H-133 Arvin Models 150TC, 151TC Kadette Model 90 Duplex RCA-Victor "Magic Brain" Model 281 Grunow 11A Chassis 11-Tube All-Wave Superheterodyne Sears, Roebuck & Co., Silvertone "Rocket" Models 6110 and 6111 General Electric Model GD-52 Zenith Models 6D302, 6D311, 6D326, 6D336, 6D360 Allied Radio, Knight Model E10913 Arvin Model 140P Emerson Models 501, 502, 504 Crosley Model 56TD-W Hoffman Model A500 Stewart-Warner Model 9003-B Zenith Models 6D014, 6D029 Coronet Model C-2 Sparton Models 7-46, 7-46PA, 8-46, 8-46PA Stewart-Warner Models 9001-C, D, E, F Zenith Models 5D011-5D027 Bendix Models 636A, C, D ECA Model 108 International Model 66 and 666, 6-Tube Superhet Ford-Philco Radio, Model FT9, 6-Tube Auto-Radio Receiver Howard Explorer Model W Deluxe 19 Tube All-Wave Superhet RCA Victor Portable Table Electrola Model R-95 Atwater Kent Model 305Z 5-Tube 32 V. D.C. Superhet Kadette Jewel Model 40 Chassis 3-Tube Ultra-Midget Receivers General Electric Model N-60 6-Tube Auto Superheterodyne Sparton Model 40 6-Tube T.R.F. Automotive Receiver Clarion "Replacement" Chassis, Model AC-160 A.V.C. Superheterodyne Emerson Models 20A and 25A General Electric K-40A Pilot Model B-2 RCA-Victor Radiola Model M-30 Automotive Radio Motovox Models 10A All-Electric and 10E Battery-Operated "Moto-Tetradynes" Kennedy Superheterodyne Short-Wave Converter RCA Victor Model R-78 B1-Acoustic 12-Tube Philco Model 15 Series, 11-Tube Superheterodyne Chassis Zenith Challenger Model 740

Sparton Selectronne Receivers Models 1068 and 1068X Fada Model 155 Super Fadalette A.C.-D.C. Set Clarion De Luxe Models AC-280 and 25-280 Crosley Model A-157 (River Roamio) Auto Radio Philco Model '37-116 Codes 121 (Shadometer) and 122 (Dial Tuning) Arvin Model 28 Philco Model 818 Fada Model 266 Motoset Bosch Models 736, 737, 738 RCA-Victor Model 15U, Radio-Phonograph Sparton Models 566 ("Bluebird" Mirror), A.C.-D.C. 5-Tube 2-Band Midget Superhet Atwater Kent Model 776 6-Tube Auto Radio Stromberg-Carlson No. 61 4-Band 7-Tube A.C.-D.C. Receiver Arvin Model 182TFM Crosley Model 58TK Westinghouse Model H-165 General Electric Models G-105 and G-106 Silvertone "F," "FF," "G," "H," and "J" Stewart-Warner Model 03-5A1 to 03-5A9 (Chassis 03-5A) Senior Varsity Radio Radiola Models 61-6, 61-7 Westinghouse Models H-104, H-105, H-107, H-108 Farnsworth Models EC-260, EK-262, EK-263, EK-264, EK-265 United Models 980744, 980745 Stewart-Warner (R-127 Chassis) Models 1271 to 1279 All-Wave ERLA Model 4500 Dual-Wave T.R.F. 4-Tube A.C. Receiver Clarion No. TC-31 5-Tube A.C.-D.C. Superhet. Detrola Model 105C 5-Tube Dual-Band A.C.-D.C. Zenith 6-Tube All-Wave Chassis No. 5634 RCA Victor Model 261, 555 to 107 Meter Philco Model 38-116; Code 125 Stewart-Warner "Ferrodyne" Chassis Model R-136 American-Bosch Model 43OT 5-Tube 3-Band Superheterodyne RCA Victor Model C9-4 9-Tube 3-Band Superheterodyne Kennedy "Model 826B" Combination Receiver Steinite 50-A and 102-A Pilot Model 63 All-Wave 6-Tube Superheterodyne Stromberg-Carlson No. 69 4-Tube All-Wave Superhet. Selector (Converter) RCA Victor Model 102 4-Tube A.C.-D.C. T.R.F. Receiver Bosch Models 60 and 61 Atwater Kent Models 30, 33, 35, 48 and 49 Crosley Model 120 Senior Superheterodyne (Pliodynatron) Chassis Columbia Screen-Grid 8 Receiver General Electric Models A82 and A87, 8-Metal-Tube All-Wave A.C. Superhet. Colonial 31 and 32 D.C. Zenith 5-Tube Triple-Wave Chassis nos. 5508 and 5509 Remler Model 46 ("Scottie") General Electric FA-60 and FA-61 Stewart-Warner Series 900 Howard Model B-5 (715), Series 1 and 2 (Sheaffer Radio-Clock-Pen Desk Set) Ford-Philco Car-Radio Models F-1440 and F-1442 Brunswick Model 31 Combination Radio and Panatrope Emerson Models 38, 42 and 49, 6-Tube Dual-Wave (Chassis U6) General Motors Chevrolet No. 601574 Automotive RCA Victor M-104 (and M-108) Automotive Arvin-Ford 17-A Automotive Westinghouse Model WR 207 & WR 208 5-Tube Dual-Band Superheterodyne Radiolas "Super VIII" (AR-810, "Semi-Portable" (AR-812), 24 and 26 Howard Model 45 A. V. C. Majestic Model 25 Galvin Motorola Model 61 Arvin Model 6 Admiral Models 7T06, 7T12 Garod Model 5A1 Hoffman Model A301 Knight Model E10716 Battery Portable Arvin Models 555, 555A, 552N, 552AN Grantline Models 605, 606 Truetone Model D2616 Belmont Model 5D128 Arvin Models 444, 444A International Kadette Model 1019 Stewart-Warner Models 97-561 to 97-569 General Electric Model 280 Zenith Models 5R080, 5R086 Truetone Models D1747, D1748 Crosley Roamio Automotive T.R.F. Models 90, 91, 92 Crosley Roamio Automotive Superheterodyne Models 95, 96 Wells-Gardner Series 062 Emerson Model AZ-196 Belmont Model 5P19 Crosley Model 56FC Emerson Models 507, 509, 518, 522, 535 Garod Model 6AU-1 General Electric Models 219, 202, 221 Crosley "Chairside" Model 567 Belmont Model 408 Battery "Farm" Wards Model 74BR-1055A Farnsworth Models EK-081, EK-082, EK-083, EK-681 Philco Model 200-X Radio Admiral "Aeroscope" Models 161-5L, 162-5L and 163-5L Philco Model 59, 4-Tube A.C. Midget Superheterodyne Zenith Farm Model 6V 27, 6-Tube Superhet Ward 10-Tube All-Wave High-Fidelity Superhet, Series ODM Philco-Packard Deluxe Canadian Westinghouse Model 175 Crosley Model 1155 Philco Models 39 and 39A Arvin Model 35 8-Tube Car-Radio Hetro Air-Ace Series M Westinghouse Models H-161, H-168, H-168A Garod Model 5A4 Arvin Models 152T, 153T Belmont Model 5240 Mantola Models 92505, 92506 General Electric Models 102, 102W, 107, 107W, 114, 114W, 115, 115W Crosley Model 555 (A.F.M.) Crosley Model 515 (Fiver) Crosley Model 425 (Travo) Firestone-Stewart-Warner Model R1332 Fairbanks-Morse Model 81 "Farm" Set Clarion Model 423, 470, 471, 472, 480 International Radio Corp. Model 90 Belmont Model 578 Series A