John Eng's Dead Tech Rescue

1945-1959 Post War Tube Radios

Page 2

1945-1950

Post War Plastic and Portable Radios with Prewar Electronic Designs

With all the inventory of 1940-41 parts and not much time to retool with newer technology, manufacturers had to convince customers that what they were buying is the latest. SOLUTION cover up the old stuff with a nicer cabinet with a modern look. Plastic made that easier to do than traditional wood.

The photo shows two Sentinel Radios. The radios on the left is the model 343 made in 1952 and the radio on the right is the model 313 made in 1949.

The chassis on the left is the model 313 (1949) using prewar technology and the chassis on the right is model 343 (1952) using post war technology.

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Table Sets

Carry Over Models from 1942

A few popular styles from the pre-war period were continued into the post war.

FADA 1000 Bullet (1946) Catalin carryover from 1942 (Highly collectible). A six tube transformerless radio with an untunned RF amplifier stage.

How to identify a CATALIN- The light shines through!

Belmont 6D111 (1946-47)- Belmont Radio Chicago, Div of Raytheon Corp. Carry over from the model 638 in 1942. Raytheon acquired Belmont after WW2 to build small radios with miniature tubes and later transistors. This popular model (often seen as reproductions) has unusual quarter round dial and push button tuning. A six tube transformerless radio with an untunned RF amplifier stage.
BELOW is a Coronado C640 (had tubes labeled Coronado) made by Belmont for Gamble's Department Stores. Identical to 6D111.
The white push button is a reproduction to replace a missing one. All the push buttons can be set. Takes a little practice to set them.

Top view of chassis. All the tube types and serial number are stamped on the chassis, a nice touch. The push button tuning mechanism is on the top left.

Total restoration underneath chassis. All paper capacitors restuffed with new ones. Dog bone resistor out of tolerance are corrected with a new resistor in parallel underneath the dog bone resistor.

Pre 1950 Post War Cabinet Table Sets

Zenith 6D015 Consoltone (1946), Zenith Radio, Chicago. 6 Tube transformerless radio with unique red power on indicator. Has RF stage using 12SJ7 tube, but is untuned- so no improvement in selectivity.

POWER ON!

Narrow Chassis. Octal tubes make servicing radio moderately difficult. Partial restore done as old capacitors were packed in tightly making wiring cramped. Notice the single control at the bottom. The tunning is the outer shaft and volume is inner shaft. This feature may look stylish, was an annoyance as turning the volume would turn the turn the tunning shaft.

From Canada

Eaton's Aurora 481B made for Eaton's Dept Store by Thorcraft (Thorkelson Radio Co, Winnepeg). early 1950s. Eaton's was once Canada's largest retailer, founded in Toronto. This is a typical AA5 radio using the octal based AA5. The IF frequency is 456 KHz, which is unusual for a 1950s radio.

Dial Glow

ABOVE: Complete restoration, most capacitors made in Canada by Aerovox (AVX). New caps were inserted into old bodies. BELOW: Chassis and parts were cleaned and polished. Typical AA5 octal base tube set

Back Cover

Below chassis front view of Belmont 6D111 / Coronado C640

The cabinet was in very good condition. All that was needed is resurfacing, buffing and polish

The antenna coil is still intact but the back was deteriorating. Made a hard board copy glued it to original back which strengthened and preserved the integrity.

Dial light illumination.

BELOW: Hoffman A200 with all pre-war technology except the use of a PM speaker.

BELOW: Pulley restore. The A200 plastic pulley wheel deteriorated and had to be removed and a new one made. The new pulley wheel was made from a round wood cap with a carved out track, The axel that supports the pulley made with a cotter pin.

More Pre 1950 Post War Cabinet Table Sets

Sonora RBMU-177 (1947) Sonora Radio and Television Corp, New York. Ivory Painted Bakelite. Replaces RBU-177 (which uses octal AA5 tubes). This radio used a few war surplus parts. Military grade ceramic tube sockets with shield mounts, large wattage resistors of different makes and cloth covered wire. This AA5 miniature tube radio uses the 50B5, forerunner of 50C5.

Economical Model. Sonora seems always design one adjustable tuned IF transformer and one fixed tuned under chassis type when marketing entry level sets. This similar design is found in entry level Japanese imports about 10 years later.

WAR surplus parts. All military grade ceramic tube sockets with shield mounts and high wattage resistors of different makes. Did an almost complete restoration on the wiring. This model uses all postwar miniature AA5 tubes.

Sentinel Companions (1949), Sentinel Radio and Television, Evanston, IL Left 315W FM/AM Using FreModyne FM Design and Right 313 AM Radios.
The model 313 is a 6 tube transformerless AM radio. All six tubes are prewar octal tubes. The sixth tube used as a untuned RF amplifier. See SHOWCASE for more info on the model 315.

BELOW: Top and under chassis wiring of model 313. Notice that the IF transformers are JW Miller replacements. A normal restoration installing new more reliable parts.

Lafayette RML-114 (1947), Lafayette Radio and Electronics, New York. Transformerless Table Bakelite using less common LOCTAL AA5 tubes (50A5, 35Y4, 14B6, 14A7 and 14Q7). Probably a kit radio- a rather large radio for the time period.

AA5 with all Loctal based tubes are not that common. Usually I see them with at least one or two octal tubes (usually the rectifier and power amplifier).

Photo of RML-114 with dial light glowing

Hoffman A200 (1946)- Hoffman Radio and Television, Los Angeles CA. Five tube AA5 radio using 12SA7, 12SG7, 12SQ7, 35Z5GT and 50L6GT vacuum tubes, Les Hoffman bought Mission Bell Radio toward the end of WW2. Their first models were the A100, A200, A300 and A400 radio phonograph.

All Hoffman radios have lighted dials.

BELOW: Complete estoration. Chassis cleaned and polish. All capacitors cleaned out and new parts stuffed inside. Resistors checked, non working speaker repaired,

Portable Radios

Portable Radios with low drain miniature battery tubes designed before WW2 did not have design issues and could move forward with upgrades inside and out.

Sonora 101 (1949) Lunchbox Style. Sonora Radio and Television Corp, New York. A 4 tube battery only portable radio.

With the exception of a newer electrolytic, the original wax coated paper capacitors are all good, thanks to the lower operating temperature of battery tubes, preserves the seal integrity of the capacitors. Most of the time I have no need to restore them.

The tubes used are 1R5, 1U4, 1U5 and 3S4. The 3S4 would be replaced in later years with a better performing 3Q4 and 3V4 tubes.

ABOVE: Notice the punch out hole between the two tubes, another large hole next to the tunning capacitor and a small holes near the speaker. These are for the model 102 AC and DC portable (se below). The holes are for the 117Z3 rectifier tube, 4-section electrolytic and power resistor divider.

Sonora 102 (1949) Lunchbox Style. Sonora Radio and Television Corp, New York. A 5 tube ac/battery portable radio. Uses a 117Z3 rectifier tube to operate 112 VAC line voltage. The other 4 tubes are the same as the model 101 above.

ABOVE: The tallest tube is the 117Z3 rectifier. By the 1950s, this tube will be replaced with s solid state selenium rectifier.

ABOVE: The 117Z3 is the only tube with a noticeable glow.

BELOW: The original electrolytic (silver) has a value of 4 x 10uf 350 WVDC. The cardboard covering says 2 x 30uf 150 WVDC, 50uf 150 WVDC and 100uf at 25 WVDC. STRANGE, capacitor made by Sprague,

Sentinel 286PMI and 286PR "Treasure Chest" (1947) Sentinel radio and Television, Evanston IL. Treasure Chest Series 3 Way Portable.
Lift the lid to turn on and the lid is an antenna and dust cover.

Chassis after cabinet, front and back removed. The selenium rectifier shown on the far left below means this is a model 286PR. The 286P uses a tube rectifier.

BELOW of the Sentinel 286PMI and 286PR wiring is tight, so component replacement is a chore.

BELOW: The Sonora 101 is battery only. Uses a 4 1/2 v "A" battery and 67 1/2 v "B" battery as shown.

BELOW: Arvin 240P,: Large paper capacitors indicate prewar parts. Rare use of a 1LB4 loctal prewar tube to save battery life and use standard D cell battery.

BELOW: Complete restoration- all capacitors including electrolytic have been restuffed with new parts.

Other views with the lid closed

BELOW: Earlier models has recessed gold lettering while later versions had raised letters unpainted.

Arvin 240P (1948) Lunchbox Portable.Noblitt Sparks Industries, Columbus, Indiana. Unusual vertical dial. For some reason, horizontal seems more popular. Pre 1950 portables used bakelite materials for cabinets. This set used typical 1R5, 1U4 and 1U5 miniature tubes. However the output tube is the loctal 1LB4, probably to keep A battery drain low and still use 1.5 V. The set is powered by 3- 1.5 V D cells in parallel and a 67.5 V B battery.

Midget Radios

Sonora WJU-252 (1947) Sonora Radio and Television, New York. Four tube midget superheterodyne painted bakelite radio. Uses 35W4, 12BE6, 12AT6 and 50B5 (later redesigned for UL safety requirements to be 50C5).

Tubes glowing. This model uses a 12BE6 as oscillator and converter. Other sets used a 12AU6 as an oscillator and converter. Lack of an IF amplifier makes sensitivity and selectivity poor.

Sonora switched over to miniature tubes quickly, but there is a single prewar IF transformer. This model uses a 3 1/2 inch speaker. The antenna lead was attached to the line cord.

Modern film capacitors replaced bulky and space hog paper capacitors. The original layout was very cramped and hard to service.

Early AM / FM Radios

THE FM STANDARD WARS

Armstrong versus RCA giant and David Sarnoff

Zenith 7H820 (1948) Rare Dual FM Band Radio- FM45, FM100 / AM (RARE). After WW2, the FM allocation war between inventor Edwin Armstrong and the radio manufacturers, lead by RCA temporarily forced manufacturers to provide dual FM bands (FM45: 42-48.5 MHz and FM100: 88-108 MHz). By the end of 1948 only 88-108 MHz band was used.

This model features the early use of solid state rectifier (selenium) and the first Zenith to use all miniature tubes (2-12BA6, 1-12BE6, 1-12AU6, 19T8 and 35B5 (35C5).

This Radio is the first Zenith table model that features the circular dial surrounding the speaker. This model features the "atomic" age styling, the see through plastic dials that seem to float in air (1940's holographic look).

"FreModyne" FM Design by Hazeltine Corporation

Selling the new FM band but saving money

Other Early AM FM radios

AM and FM radios were expensive and was not as popular as AM only radios. It would take Americans over two decades to fall in love with FM. Early radio models that aerethe more expensive RCA patented superheterodynes used a dicriminator detection instead of the ratio detector common in FM sets now. For the more budget AM and FM radios a superregenerative FM design call FreModyne was used for a very short time.

Sonora WEU-240 (1948) Sonora Radio and Television, New York. Early Hi Band FM/AM Radio. Transformerless 8 tube set.

Spacious chassis, mix of octal and miniature tubes.Left to Right 6BA6, 6BE6, 6BA6, 6BA6, 6SQ7GT, 6AL5, 25L6GT and 25Z6GT

Sentinel 315W FM/AM Radio of 1949 The invention of FM transmission and reception by Edwin Armstrong ushered in static free radio broadcasts. However the superheterodyne design required a lot of parts and required paying royalties. The Hazeltine Corporation invented a low cost approach through a modified design of Armstrong's superegenerative invention that was now public domain. Hazeltine designed a low cost FM tuner using superegenerative design and patented the FreModyne. Though it lacked the sensitivity and noise free properties of superheterodyne FM, it provided a simple low cost approach to having an FM radio for the consumer. This bought some time for radio manufacturers to catch up during the early post war period by featuring new post war inventions using prewar engineering. The FreModyne lasted for a VERY short time, by early 1950 virtually all FM was superheterodyne. If you look above in the radio photo gallery you will notice that this model has the same cabinet as the 313. Your guess!!!!!!

WEU-240 dial light glow. Tuning knob is directly under dial pointer with band selector to the right of it. Other knobs to the left are volume and tone. BELOW RCA 2-XF-91 side view.

RCA 2-XF-91 (The Forbes)- Rca Victor, Camden NJ. Transformerless 8 Tube AM/FM Radio with separate AM and FM dial pointers moving on opposite directions.

ABOVE: Tubes and IF transformers. Radio uses 19X8 AM / FM Osc -Conv, 6BJ6 AM / FM RF. 2- 12AU6 FM IF, 12BA6, AM IF, 12AL5 Det / Discriminator, 12AV6 AM Det and 1st Audio and 35C5 Power Amp. Solid state rectifier replaces tube. Originally Selenium, replaced with Silicon rectifier. LEFT: Upper- Tuner Cavity- both AM and FM components wired around the 19X8 Mixer-Converter tube. FM oscillator frequency is accomplished by stretching or compressing the coil. LEFT: Lower- Rest of the wiring, modern capacitors replaced paper and molded capacitors.

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