Zenith console

zenith console

Zenith Model 12-S-471 Console Radio (1940)

With its sleek styling and black "robot" dial, this large Zenith 12-S-471 console typifies a great design period in radio history. Put a high-performance 12-tube chassis inside this luxurious cabinet and you have an unforgettable combination.

It took a fair amount of work to realize this radio's potential. The first picture shows the set on the day when I bought it. The second shows it after restoration.

Most of the cabinet was in decent shape, with small nicks and scratches here and there. The top had some discoloration and flaking, probably from flowerpots.

In the first photo, the chassis had been removed and placed on top of the cabinet. I don't always remove a radio's chassis for transport, but this set required careful treatment. The chassis is mounted on springs, normally held in tension by large mounting screws through the support shelf. Somebody had removed and lost the mounting screws, allowing the chassis to bounce on its springs like a rocking horse! Had I not removed the chassis, the dial might have smashed the dial glass by the time I got home.

The next photo shows the chassis as found, complete with a thick layer of vintage dust.

The owner said that the radio had played beautifully until one day he saw "a lot of sparks in back." He quickly unplugged the radio and had not tried it again. Looking at the rear, I saw that the power cord had frayed down to bare wire where it entered the chassis, causing a short circuit.

Putting on a dour expression, I explained to the owner that virtually all 50-year old radios require a thorough overhaul, and that a radio of this complexity might take many hours to rebuild. I also pointed out various dents and scratches on the cabinet, as well as a couple of chipped pushbuttons. By the time I was done, the price had been cut in half! We made a deal and I brought my prize home.

Description

Model 12-S-471 ranked near the top of the Zenith product line in 1940. Here is its description in a dealer's brochure:

Twelve-tube superheterodyne with Rotor Wavemagnet Aerial; Radiorgan; Automatic Tuning; Television Sound connection; Triple Spectrum Robot Dial; Outer Circle R.F. Circuit; 12-inch speaker; receives American, foreign broadcasts, police, amateurs, aviation, ships. 42 inches high. Walnut finish. $119.95.

The next photos show the ample 12-inch speaker. Combined with two 6V6 tubes in push-pull configuration, the 12-S-471 provides powerful, room-filling audio.

The Wavemagnet moniker was used for the antennas in many Zenith radios of the 1940s and 1950s, including the TransOceanic. Although WaveMagnets took many shapes, in this case it is a multi-element antenna mounted in a box-like form with a fabric cover. You can rotate the antenna back and forth to optimize reception from a particular direction. A slide switch on the antenna lets you favor standard broadcast or shortwave reception.

The Wavemagnet appears at lower left in the rear view:

Hanging from a terminal screw is a round green paper tag with instructions for connecting an external antenna.

As the rear view shows, the chassis of this radio is unusually tall. Zenith ads dubbed this the Super Goliath chassis, "generously oversize. a promise of impressive performance. Beautiful hammered gold finish. spring floated in cabinet ."

Even the tube shields were painted to match the hammered gold chassis color, a feature shared by my Zenith 6-J-230 tombstone.

The next photo gives a closer view of the dial and pushbuttons. On the left are the On and Off buttons, plus six tone buttons (Voice, Normal, Treble, Alto, Bass, and Lo Bass). The automatic tuning buttons are on the right.

Radiorgan was Zenith's trade name for a group of tone control buttons. Here is a breathless description from their sales literature:

Radiorgan brings new tone fidelity. new tone mastery. 64 tonal combinations! Now, hand-in-hand with the mastery of time and space. the mastery of tone is yours as well! Here is an organ keyboard that lets you choose high notes, brilliantly expressive, and low notes, deep and sonorous, all in their proper proportion. You can press in and pull out the "stops" of the Radiorgan keyboard to your heart's content. You can obtain an endless variation of "acoustic symmetries!" You choose them. with any kind of music. orchestra. string. brass. vocal. as you wish. when you wish.

Automatic tuning was provided through a set of eight pushbuttons that could be set to favorite stations. Pushbutton tuning was found in many other radios, such as my Stewart-Warner tombstone. Zenith ads claimed that this company was the first to introduce this feature, in 1928.

Zenith made their pushbuttons a bit easier to tune than did other companies. On many radios, you need to adjust two components—a coil and a trimmer capacitor—for each station. This radio has only





one adjuster per station; perhaps the coil and trimmer are ganged together on a single screw.

The Television Sound connector mentioned in the ad is a simple audio input jack on the back of the chassis. Here is Zenith's description of the feature:

Your 1945 Radio Here Now! Television Sound Connection—which means you can buy Zenith for the future with confidence. When television comes. you will be ready for it.

The TV Sound Connector was a hedge against obsolescence. Television broadcasting was largely experimental before World War II, and affordable TVs were not available until the late 1940s. A tiny number of prewar TVs were manufactured with no audio section, to reduce their cost. You plugged them into a radio or phono amplifier to hear the sound.

For a few years, some manufacturers offered a Television connector for this purpose. I suspect that very few of these connectors were used in practice. From the late 1940s onward, TVs included their own audio amplifiers.

Had Zenith been able to predict the future, they would also have known that there would be no such thing as a "1945 radio" for non-military customers. When the United States entered World War II, all domestic radio manufacturing was diverted to war production. The wartime moratorium was not lifted until 1946.

Collectors usually refer to the "Triple Spectrum Robot Dial" as a shutter dial or clamshell dial. Zenith used the term "robot" for a few different dial types over the years, and most robot dials did not use the shutter mechanism. Here is a description of the 1940 dial from a Zenith brochure:

Robot Dial. the dial that is three dials! Extreme simplicity in tuning all short wave and foreign broadcasts. Now all wave bands have separate, full sized dials. Just one clear, easy-to-read dial is visible at a time. The lever automatically changes the bands and pops up a complete new dial for each band.

This radio offers continuous coverage from .55 to 18 Mhz using three bands, labeled Broadcast (.55-1.6 Mhz), Medium wave (1.7-5.6 Mhz), and Shortwave (5-18 Mhz). The clever shutter dial employs three split dials, one for each band. The dials are arranged in a stack with the broadcast dial in the frontmost position. Each dial is a different color: black for the BC band, gold for shortwave, and a beautiful electric blue for medium wave.

Here's a view of the 12-S-471 dial set to the Broadcast band. You can also see the 6U5 magic eye tuning indicator.

When you switch from Broadcast to Shortwave, the Broadcast dial opens like a shutter in the middle and its halves disappear to the sides, exposing the Shortwave dial behind it. When you switch to the Medium wave band, the second dial disappears and exposes the innermost third dial.

The shutter mechanism was ingenious but expensive to manufacture. After a year or two, Zenith abandoned the shutters and went back to a single dial face, in which all bands are visible at all times.

Electronic Restoration

Below are two views of the 12-S-471 chassis after restoration. I put temporary blue tags on the automatic tuner leads to avoid mixing them up.

My radio's electronics were complete and in pretty good condition. The shorted power cord was responsible for the fireworks seen by the previous owner. After replacing the cord and cleaning things up, I slowly brought up the power on my variac. I was delighted to hear some local stations loud and clear. I quickly powered down the set, not to restart it until I had rebuilt the power supply.

Removing the chassis from the cabinet is a bit of a production. The first step, of course, is to remove the two knobs and the bandswitch lever, which are held on with setscrews.

The pushbutton bezels are held by small spring-loaded pins on their inner sides. Push in the pin and slide the bezel slightly toward the middle of the dial. The left assembly can be carefully turned and slid back through its hole. The right bezel will come off completely.

After you remove both bezels, you need to remove eight tiny screws and then take off the big dial bezel with its glass cover. That exposes mounting screws for the right tuner pushbutton assembly. Once those have been removed, you can unscrew the chassis mounting bolts from underneath and slide the chassis back and out.

Cleaning involved removing dust and grime from the chassis, using DeOxit electronic cleaner on the controls, and lubricating moving parts such as the tuner drive and band-changing mechanism.

All twelve tubes tested OK on my tester, but the two 6K7G tubes were weak enough to warrant replacement. I ordered new ones through the mail along with a copy of the schematic .

Zenith used this type 1207 chassis in five different cabinets, including the 12-S-471. Here is a list of its tubes and their functions:

Source: www.antiqueradio.org

Category: Other

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