You’ve just acquired an old radio, but apart from the manufacturer’s name on the front, you don’t know a blessed thing about it. Learning more about your radio may satisfy your curiosity, or it may serve a practical purpose such as helping you get repair information. Here’s how to go about identifying an antique or vintage radio, and then how to decide if it’s playable.
Identifying Radios By Manufacturer, Name, and Model Numbers
Tens of thousands of different radio models were manufactured over the decades, in the US alone. Many thousands more were manufactured worldwide. Most of the radios sold over those decades are not very interesting. For every rare and unusual radio, there were thousands of cheap and common radios.
The normal way to identify a radio is by manufacturer and model number (for example, “Zenith 7G605″ or “Philco 42-350″). Model numbers can include any combination of letters and numbers, and they may be long or short, although most are from two to six characters in length. There is no standardization whatsoever for model numbers. Every manufacturer was free to make up its own scheme, and often a given manufacturer would change its numbering scheme over the years.
Model numbers are often printed on a paper label attached to the back, inside, or bottom of the radio cabinet. The label usually contains other information, such as a serial number, tube diagram, or even a complete schematic diagram. The model number may also be printed somewhere on the cabinet itself. On my Zenith TransOceanic H500, the number is printed in white ink inside the hinged back cover.
Most radios also list various patent numbers. These are pretty useless for identification, because virtually all radio makers licensed several technology patents from other manufacturers, and they were required by law to disclose those patent licenses. If you look at a bunch of old radios, you’ll see that many of them list exactly the same patents.
Patent notices often include dates, but those do not tell you when the radio was made. They only indicate when the patent was originally granted, which could be many years earlier. So a patent date merely tells you that the radio could not have been made before that date.
Some radios have a name in addition to (or, occasionally, instead of) a model number. For instance, my Crosley F5-TWE was known as the “Musical Chef,” and that name is actually printed on the front of its cabinet. Hundreds of different names were used over the decades—everything from the predictable (“Globetrotter”) to the alliterative (Zenith “Zenette”) to the fanciful (“Phantom Baby”). The name may be handy if a collector guide happens to list your set by name instead of by model number.
Resources for Identifying Your Old Radio
Collector books list thousands of radios, often with approximate values. The Slusser (formerly Bunis) collector guide is one of the most popular, although it’s by no means the only show in town.
Technical service publications are another great source of information. These include Rider’s, Sams Photofacts, Most Needed Radio Diagrams, and so on. Technical references were published for radio repair shops and they are still to be found in many public libraries.
Radio collectors may be able to help. If you haven’t already done so, look for a radio collector club in your vicinity. The Antique Radio Classified website has an extensive list of clubs in North America.
Newsgroups. If there’s no club nearby, another possibility is the USENET newsgroup rec.antiques.radio+phono. Although that group is concerned mainly with technical discussions, some members are willing to help with identifications.
Websites. When I launched my site in August, 1995, there was only one other website like it in the world. Now there are dozens, with more appearing all the time. A radio website might happen to show your radio, or perhaps its webmaster is willing to field your question. Speaking of which—if you’ve tried all these channels and struck out, feel free to send me some email. I usually have time to make a quick scan of my collector books to see if a radio is listed.
Other Identifying Features
Even if your radio has lost its label or logo, or perhaps never had them to begin with, you can still identify the set, though it may take some detective work. Here’s some things to look at:
Component markings. If the outside lacks identifiers, the inside may still hold clues. Look inside the chassis—if you see the same manufacturer’s name stamped on all the tubes and other components, that’s a tipoff. On the other hand, it’s not unusual to see a mixture of brand names on components. Many manufacturers got components from other suppliers. And radios that were repaired over the years often have a random assortment of replacement parts under the hood.
Cabinet design. Often a strong indicator of when a radio was made. The very earliest radios were typically bare components mounted on a board. Somewhat later, many were housed in comparatively plain wooden or metal boxes. By the late 1920s, some were housed in elaborate cabinets designed to look like “real furniture” instead of electronic gear. Cathedral and tombstone style wooden cabinets were most popular during the 1930s. The 1940s were the heyday of “Machine Age” and other design trends.
Cabinet materials. 1920s radios were typically housed in wood, although some tabletops came in rather plain metal cabinets. Bakelite and Catalin were the most popular synthetic materials during the 1930s and 1940s. Other early plastics, such as Plaskon and Beetle, predated the flood of new synthetics that came along during the 1950s. Wooden cabinets were used during all periods from the 1920s to the present.
Dial Markings. The band and frequency markings on the dial can tell you something about a radio’s age. The earliest 1920s radios did not show any station numbers; instead, their knobs were marked with numbers from 0-100 or sometimes nothing at all. If your radio has a band marked Police or Aircraft, it was probably made before World War II; those frequencies are no longer used for such communications. Shortwave radio was common from early days, but FM broadcasting wasn’t developed until the 1930s. The FM band frequencies were changed after World War II, so if you have a radio that tunes FM from 42-50 megahertz rather than the modern 88-108 megahertz band, you know it was manufactured before 1942. A radio that has FM stereo was made in the late 1950s at the earliest. Civil Defense (CD) markings on the AM dial at 640 and 1240 kilohertz indicate that the radio was made between 1953 and 1963.
Tubes. The very oldest radio vacuum tubes looked more like light bulbs and had screw-type connections. Most 1920s tubes had glass envelopes and large bakelite bases with four or five pins. 1930s and 1940s tubes typically had glass or metal envelopes and six, seven, or eight pins. Locking (“loktal”) metal bases were used for a few years in the late 1940s. They were superseded in the 1950s by all-glass “miniature” tubes with very thin pins. Keep in mind that different tube types overlapped. For example, some radios continued to use loktal or older tube types into the 1950s. However, if your radio uses glass miniature tubes, you know it must have been made after the end of World War II, and was likely made in the 1950s or later.
Transistors. Transistors were introduced in 1957, so every transistor radio is dated after that time. Transistors didn’t become common until the 1960s.
Before Turning On Your Radio
If you just brought home an antique radio, you’re probably dying to play it immediately. That could be an expensive mistake unless the set was professionally repaired before you bought it. If the radio has a short circuit or defective component, turning it on could further damage the set or even start a fire. You should always check an unknown radio for gross problems before you turn it on—otherwise, “firing it up” might be a sadly literal experience!
A few problems can be spotted visually. For example, if the power cord is broken, cracked, or frayed, you must replace it before trying to plug in the radio. Some other problems can be spotted by looking at the chassis. (This is the metal box inside the cabinet, upon which other components are mounted.)
Some radios have backs and others don’t. If the radio has a back, you’ll need to remove it to inspect the components (tubes, etc.) on top of the chassis. The cabinet back is usually attached with a handful of small screws or clips. As you remove it, be careful not to break any antenna wires that may be attached. Some newer radios will have an integrated connector for the power cord, which unplugs the cord from the chassis as you (gently!) remove the back.
After the back has been removed, you should look for gross problems include missing or broken tubes, and anything else that’s obviously absent, broken, disconnected, fried, or massively corroded. If you see any of these signs, count on repairing the set before you power it up.
In almost all cases, the radio’s electronic components—tubes, capacitors, resistors, etc.—will look exactly the same whether they have failed completely or they are working perfectly. When a radio is turned off, a dead tube looks just like a good one. A shorted capacitor looks just like a good one, and so on.
Many experienced restorers would not bother trying out the radio at this stage. Instead, they would remove the chassis and routinely replace most or all of the old capacitors. If you’re a beginner, you won’t learn anything useful by looking under the chassis. And plugging in the radio outside the cabinet will only increase your risk of getting an electrical shock. But you can read all about this process in my article Replacing Capacitors in Old Radios. Whether you want to take this cautious approach is up to you.
Let’s assume that either you have finished the capacitor replacement or you’re willing to risk firing up the radio as-is. Either way, most restorers will power up the radio using a gadget called a variac which lets you slowly increase the voltage, watching for any danger signs along the way. If you don’t have a variac, you can use an inexpensive homemade substitute. Our Dim-Bulb Tester page gives directions on building and using such a device. In addition to increasing the voltage by increments, a dim-bulb tester can also warn you of short circuits in the radio’s power supply.
If you don’t have either one, you can simply turn on the power switch and cross your fingers, but I advise against that practice, for all the reasons given above. Once the voltage has been increased to full power, turn the volume control up about one-third of the way and tune the radio dial to a strong local station. Within about fifteen seconds, the tubes should begin to glow with a faint orange color. (Exceptions are metal-cased tubes, which have an opaque covering, or very-low voltage tubes such as those in old Zenith TransOceanics.)
Watch closely for anything unusual as the radio warms up. A slightly hot smell is normal, especially if the radio is dusty, but a strong burning smell indicates trouble. The same goes for any sparking sounds or smoke, which usually indicates a serious problem. If the radio plays normally, take a moment to congratulate yourself, then turn it off until you have time to replace the capacitors (see above).
If you hear a loud humming sound that does not change when you turn the volume control, that is caused by failed filter capacitors in the power supply. The radio will not work until you replace them.
If it Sounds OK, Can I Use It?
You can play an unrestored radio all you want . . . if you don’t mind the risk that it will fail at any time without warning. In my experience, most unrestored radios will conk out—typically with one or more failed capacitors—before long. And if you go in to replace that failed capacitor, it’s only a short time before the next one will fail, and so on.
To get a radio that is safe and reliable to use every day, it’s best to replace all of the old capacitors at once. If you choose not to do that, I strongly advise that you never leave the room while the radio is playing, or leave it playing overnight. It’s just not worth the risk. A few unrestored radios might play for a long time without problems. Others can start on fire—it has happened to me!
Images in this article appear in the following order:
(All images courtesy Phil Nelson of Phils Old Radios)
1. Zenith TransOceanic 6G601M
2. Wooden Philco 90
3. Emerson 558 Tube Portable
4. Plastic Zephyr 1
5. Buick Trans-portable Transistor
6. Zenith Y724 Bakelite
7. Zenith TransOceanic G500
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