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

With its sleek styling and black "robot" dial, this large Zenith 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.

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 previous 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 pounded the fragile dial glass into smithereens by the time I got home.

The next photo gives a close-up view of the chassis, complete with a thick layer of vintage dust.

The owner stated that this 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 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. The rear photo also provides a look at the ample 12-inch speaker. Combined with push-pull audio, this speaker provides powerful, room-filling sound.

As the previous photo 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.

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 most 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 next photo gives a close-up 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.

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 bit of 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 other amplifier to hear the sound.

For a few years, some manufacturers offered a Television connector for this purpose. These connectors were rarely 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.

Of course, anyone with a phono player and the right connector could use the Television jack to play records, but many radios of the time included a Phono jack for that purpose.

Nowadays, the Triple Spectrum Robot Dial is popularly known as a shutter dial or clamshell dial. Zenith used the term "robot" for a few different dial types over the years. 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 mounted in a stack with the broadcast dial in the front-most position. Each dial is a different color: black for the BC band, gold for shortwave, and a beautiful electric blue for medium wave.

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. Within 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

This radio's electronics were complete as found. It had an obvious shorting problem, likely caused by the bad power cord. The rubber belt on its tuning dial had broken and had been replaced with a definitely non-authentic thin rubber band.

As I had observed, 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.

Cleaning involved getting all the dust and grime off the chassis, spraying DeOxit electronic cleaner inside all controls, and lubricating moving parts such as the tuner drive and dial-changing mechanism.

All twelve tubes tested "OK" on my simple 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. Here is a list of the tubes and their functions:

In an era when "tube count" was equated with quality, manufacturers occasionally used more tubes when fewer would do, especially in high-priced consoles. This twelve-tube radio could have used eleven tubes, or even ten, without degrading its performance. A single rectifier could have replaced the pair of 6X5 tubes. One dual-function tube could have replaced the two 6J5Gs that serve as detector and first audio amplifier.

Before diving into the electronics, I posted a message to the rec.antiques.radio+phono newsgroup, asking whether this set posed any particular problems in restoration. Among other advice, I got this note from Ed Engelken:

Your radio is one of the Zeniths that uses a pair of 6X5 rectifier
tubes. Those tubes were famous for developing heater-to-cathode shorts.
When that happens, the power transformer is history. Don't ask how I
know this! The old-timers used to hook up a pair of #44 pilot bulbs in
series with the plate leads to the rectifier tubes to act as fuses.
This was supposed to work better (read faster) than fusing the power
transformer primary. Perhaps a separate small filament transformer
under the chassis feeding the 6X5's would be a good idea. Just don't
connect the heater circuit to ground - let it float.

Peter Bertini offered another perspective on the rectifier issue:

I have never used the #44 lamp trick, since a 6X5 failure has always 
immediately blown the 1-amp line fuse I installed under chassis.

Of these three solutions—pilot lamps, transformer, or fuse—the fuse seemed easiest. The parts cost a couple of bucks at Radio Shack and took only a few minutes to install. Adding a line fuse is a good safety measure for all old radios.

I replaced the old rubber tuner belt with inexpensive O-ring material, a trick that I learned when restoring my Zenith 6-J-230. I posted the following description of the process to the antique radio newsgroup.

From: Phil Nelson
Newsgroups: rec.antiques.radio+phono
Date: Sunday, May 16, 1999 7:38 AM

I couldn't find O-ring stock or a large enough O-ring, so I bought two
smaller rings. I cut both rings on the diagonal and super-glued two ends
together, forming a longer strip of O-ring that could be trimmed to length
after wrapping it around the pulleys.

I did not disassemble the tuning mechanism. All that it needed, apart from a
belt, was cleaning & lubrication. I did clean the pulley channels with
lacquer thinner and Q-tip swabs. The O-rings seemed to have something like
silicon lubricant on them, which I also cleaned off.

To snake the new belt down onto the pulleys, I used two 12-inch lengths of
solder as helping hands. Crimp one end of each solder wire onto each end of
your new belt. From the top of the chassis, you can send one helper down
each side of the top pulley, laying the belt's middle over that pulley. The
hands were especially helpful with my homebrew belt, which wanted to curl
back into its original form. (This was all done with the chassis on its
side, of course.)

Working from the bottom, I removed the helping hand from one end of the new
belt and laid that end just over the curl of the bottom pulley. Holding that
end in place with a finger, I stretched the other end down using the helping
hand. When the tension seemed right, I grabbed that end with a needle nose
pliers at just the spot where I wanted to cut it. Then I cut the belt on a
diagonal at the marked spot.

Holding both ends in one hand, I slipped the belt off of the top pulley to
give enough slack for gluing. One SMALL drop of super glue is all you need
to cement the belt ends. (Be careful not to glue your fingers to the belt!)

Then I slipped the belt over the bottom pulley and used one of the helping
hands as a crook to pull the far loop over the top pulley. As you get the
belt partway over the top pulley, turn the tuner knob slightly to run the
belt onto the pulley.

That's it! The new belt seems strong and secure. And I didn't have to pull
apart the whole tuning mechanism. It's not too hard to "feel" the right
tension when you're measuring the belt. You want it tight enough to grip the
pulleys but not so tight that you'll wear things out prematurely.

The next day, I began replacing capacitors. As always, I started with the large electrolytic capacitors that filter the power supply, then turned to the small paper capacitors.

I also replaced the 1-megohm resistor for the magic tuning eye tube. If the value of this resistor drifts upward, as very often happens over time, the magic eye becomes unresponsive. The tiny resistor is mounted inside the base of the eye tube, wired between two pins. The next photo gives a view of the resistor in place. The red circle encloses the base, which I had loosened and slid down the cables. The red arrow points to the area where the resistor nestles among the pins.

If you replace this resistor, be careful not to break the delicate wires or pin connectors. I performed this surgery with the tube removed from its clamp and the pins secured in a "helping hands" device on the workbench. Now the magic eye became bright and responsive.

The next photo shows the chassis after recapping. You can see all of the replaced components—about 20 capacitors and a few resistors—lying in front of the chassis.

Here is a view of the restored underside.

The next step was to align the radio using my signal generator and multimeter. When that was done, the radio played like new, with outstanding sensitivity and strong audio. I was impressed with its shortwave reception using only the onboard Wavemagnet antenna. A well-designed antenna can deliver good performance in a small package.

I also adjusted the station pushbuttons, tuning each one to a favorite local station.

Cabinet Restoration

The worst part of the cabinet was the top, whose lacquer had suffered some stains and flaking. In search of better restoration techniques, I decided to try something new.

I had often read about "re-flowing" a lacquer finish but never succeeded in doing it. The idea is simple: using a mild solvent, you dissolve the old finish and spread it around until it smoothly coats the whole surface. Most of the finish on this cabinet top was still present, so I decided to give it a whirl.

With a couple of phone calls, I located an auto paint supplier in my town who sold lacquer retarder by the quart. A retarder does what it sounds like, slowing the action of lacquer as it dries. Retarder can be useful when spraying lacquer in humid conditions, to prevent lacquer "blush" caused when moisture is trapped under fast-drying lacquer.

If you mix retarder with lacquer thinner, then you have a mixture that will dissolve an old finish, but keep it from drying too fast, so that you have time to smooth it around.

That's the theory, anyway . . . .

I wasn't sure about which proportions to use, so I chose an old piece of damaged furniture to practice on. In the first experiment, I mixed one part retarder with four parts of lacquer thinner. This mixture was too strong. It acted like a slow stripper, removing most of the old finish before long.

Next experiment, I mixed retarder and thinner in equal proportions. This mixture was too mild. It took several minutes before the old finish began to dissolve. Once the old finish had loosened, it turned gummy and started to stick rather than flow. Adding more mixture only made things worse. After about fifteen minutes, I gave up, leaving an ugly finish that was dull and thin in some places, shiny and thick in others, and blotchy everywhere.

The next experiment used about one part retarder with two parts of thinner. This mixture was easier to use. It loosened the old finish after a couple of minutes and it seemed like I was smoothly re-flowing the old finish over the entire surface.

When I let the piece dry, the results were disappointing. Some areas had indeed been smoothed and coated. Others looked almost untouched, however, still showing the original scratches and dings.

There's more to this technique than simply pouring on magic liquid and pushing it around for a while. The refinishing mixture dries as you work, so you need to know when to add more mixture to keep things flowing. Temperature and humidity also affect the process. The idea is to loosen the entire old finish and smooth it evenly, but that's easier said than done!

Despite these uncertain results, I decided to try the refinishing mixture on the top of my radio cabinet. At worst, I would have to strip the top, something I'd have to do anyway. I mixed some fresh refinisher and gave it the old college try.

As in the previous trial, the final result was pretty uneven. The flaked areas that I hoped to recoat were barer than ever. Much of the original finish was still intact, but it still showed its old scars.

At this point, I became impatient and decided to strip the top. The re-flowing technique held promise, but I would need more practice!

Since I had plenty of thinner and retarder on hand, I used that as a stripper, going back to a 1:4 mixture. Applying this brew with soft rags, I soon had removed the old lacquer. I did this operation with the cabinet lying on its back, to avoid spilling stripper on the sides and front of the cabinet. I stopped wiping before I had removed all of the color and original filler, although the top now looked significantly lighter than the rest of the cabinet.

I let the top dry for an hour, then wiped on a thin coat of Min-Wax Special Walnut stain. This evened the color on the top. Using Q-tip cotton swabs, I also applied small amounts of stain to scratches elsewhere on the cabinet. If you apply just the right amount of stain, the scratch will be erased almost completely. A few trim areas on the cabinet have a contrasting, extremely dark brown color. One such area is the edge of the circular dial surround. I touched up scratches in these spots with a Min-Wax Dark Walnut stain pencil. After the stain had set for a few minutes, I wiped off the excess and buffed it dry with a clean cloth. Then I let the cabinet dry overnight.

The next day, I masked the remainder of the cabinet and sprayed several coats of Mohawk Perfect Brown toner lacquer on the top. This operation darkened the top to match the cabinet body. Toning lacquer is the same thing that manufacturers used to color cabinets, so the result will be authentic.

I removed the mask and examined the entire cabinet in strong light. The color match was close, but not perfect. The new toner on top was slightly redder than the original color. Working with care, I applied a very light coat of toner to the rest of the cabinet. I blended it carefully, applying more to the top areas than to the bottom. This light toner coat also blended the scratch repairs, making them disappear completely into the surrounding finish.

Lastly, I applied several finish coats of clear lacquer. In between every lacquer coat (including toner), I lightly buffed the whole cabinet with #0000 steel wool and wiped it with a tack rag. Although lacquer dries very quickly, you can see that applying a number of coats is a time-consuming process.

The next photo shows the restored cabinet.

The grain of the veener is exceptionally pretty. Contrasting burled strips adorn the sides and the decorative front-piece uses alternating grained strips to accentuate the diagonal lines of the cutouts.

Not every cabinet requires this much work. A very nice one may need nothing but cleaning (you can use paint thinner and soft rags). Minor scratches and dings can be concealed with a stain pencil or a Q-tip dipped in stain.

Please avoid stripping an entire cabinet to bare wood and applying a non-authentic finish. Virtually all wooden radio cabinets were finished in lacquer, using a walnut or dark brown toner for color. Few things are more ugly than a vintage radio that has been given a cheap "antique mall" strip job, ending up with the color much too light and covered with ghastly polyurethane.

Final Thoughts

The work that I did was typical for a Zenith of this vintage. I could have gotten by with less cabinet work, but I wanted this set to be a showpiece in our home. Right now, it sits in a corner of my study where I can look at it every day (it's playing as I write this article, in fact).

Only one small piece was required to complete this restoration. On the outside of the dial glass, right in the middle, should be a round metal shield with an embossed Zenith logo. Its color matches the metal shield behind the dial glass, which can be seen in the dial photo.

Some time after publishing this article, I obtained the correct part from a fellow collector. Now my project was truly complete!