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| If someone were to ask what component of a car most people know the least about, it would have to be the radio. Not only is radio/electronics a mystery to many, but also the myths and legends that circulate seem to complicate things. Indeed, there are car stereo DEALERS out there who have little or no concept of what theyre even working with! |
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Article By Gary E. Tayman
If someone were to ask what component of a car most people know the least about, it would have to be the radio. Not only is radio/electronics a mystery to many, but also the myths and legends that circulate seem to complicate things. Indeed, there are car stereo DEALERS out there who have little or no concept of what they’re even working with!
As a well-known cruiser in southwest Florida who is also a CET, an FCC Radiotelephone licensee, an antique radio hobbyist, as well as a business owner that specializes in radios/stereos for collector cars, Ray has suggested I write a comment or two about my trade. I’ve decided to take it several steps further; rather than talk about myself I feel it’s more beneficial to write an article – rather a complete series – to help educate readers about these little music boxes you have in your dashboards. We’ll relive some history, discuss some basic design concepts, and provide recommendations for purchasing, servicing, and installing original car radios as well as modern aftermarket stereo systems. Without getting technical, you will be given enough information to allow you to make wise decisions about purchasing, installing, and having your radio serviced. We’ll start with the oldest and eventually work our way toward modern systems – all with the intention of helping you get the most out of that electronic gizmo, be it an 8-tube wonder or a modern mp3 docking station.
Let’s start things off with a history lesson, going back to the proverbial beginning. Before 1920, when KDKA and other stations began commercial broadcasting, radio’s main usage was in maritime, military, and industry. During World War I, around 1915-16, indeed some military vehicles were equipped with radio apparatus – the world’s first automobile radios. Car radios for consumers began around 1925, made by companies including Atwater Kent, Crosley, Philco, and Galvin (who made the “Motorola”). As you might expect these sets were primitive, clumsy, and expensive. Since the 6-volt DC car battery was inadequate to drive the tubes, they required an additional high-voltage B battery. Some models used a dynamotor – a motor/generator combination to provide the higher voltage needed in these sets. Either way, the car radio at the time was a mess, and few people owned them.
Not only were the early sets impractical, but the public was concerned about the use of car radios in general. Tuning/adjusting the set required taking your eyes off the road, and the sound of the radio could distract the driver from paying attention to his surroundings. Although these fears have later been disproved (at least by the 99% of us who use common sense), at the time it was a major concern.
If you’re into early brass vehicles and want an original period radio, you might find one of these beasts if you look hard. But it’s a novelty not practical for use. If you want it to work, you need to either become a radio hobbyist yourself, or spend lots of money and then become a hobbyist to understand how to use it. For a practical radio you’ll want something else.
The early 1930’s saw some interesting changes to radio as a whole. During the great depression radio sales took off. Why? Its entertainment predecessor, the gramophone, required you to continue purchasing records every time you wanted to hear a new song. With a radio you paid one price up front and listened to your heart’s content. Radios also got better and less expensive, and people began to overcome their fears of having a radio in the car. Plus there was an innovation milestone – the vibrator. This is a buzzer-like device that turns the 6-volt battery power into AC, allowing a transformer to boost the voltage as needed for the radio. Suddenly these sets became practical, and automakers began offering radios as factory options in their vehicles. From the early 1930’s through the late 1950’s, virtually all car radios were vibrator-powered. It’s easy to tell if it is – just turn it on. Do you hear a faint buzzing sound behind the dash? That’s the vibrator.
There’s a unique feature of vibrator-powered radios that’s worth noting – they work equally well on positive ground or negative ground electrical systems. Indeed, all Fords, Mopars, Studebakers, and certain GM cars used positive ground on their 6-volt systems – but this made no difference with the radio. In fact, the 1947-53 Chevy trucks used negative ground, while the GMC counterparts used positive ground. Both brands used the same radio. Now for some exceptions: Some 1940’s Buicks and Cadillac’s had radios with a special “synchronous” vibrator. These required the correct polarity. Also, if your radio has a modern replacement solid-state vibrator, the vibrator’s polarity must match the car.
Take my advice: if you have an original vibrator-powered radio, working or not, have it rebuilt by a professional before using it. Just like the vehicle itself – if you discover a car that’s been sitting in a barn for 30 years, give it a jump-start and it fires up, would you drive it to Chicago without doing some serious maintenance first? I don’t think so! So what goes bad in an old radio? The answer might surprise you. It’s generally not the tubes; in fact tubes have an infinite shelf life so they won’t go bad from sitting. Vibrators are failure-prone, but these are still not the big problem. So what is? Capacitors. Most capacitors from about 1955 on back are made of rolled-up foil and paper, covered with beeswax. In time moisture seeps in and contaminates them, allowing high voltages to leak and burn up other components such as tubes, vibrators, and even the power transformer – yuck! As the saying goes, you can pay now or pay much more later.
A typical rebuild consists of replacing all paper and filter capacitors, checking/replacing other components as needed, testing tubes and replacing any that test weak, and replacing the vibrator with a new solid state type. Original vibrators had an expected life of only 18 months! The new ones will last forever, if the surrounding components (such as the buffer capacitor) are good. The modern replacement capacitors are much better made and will far outlast the originals. A rebuild typically costs around $200 – miniscule compared to restoring the car’s other components -- and is well worth it. A properly rebuilt tube radio is better than new and you can use it every day without reservation. Bear in mind that the service price can go up if the radio is already damaged, or if the radio is a rusty mess pulled from a junkyard. Just like the car itself; you can expect a rust bucket to involve more restoration work than a clean car in a garage.
If you know a little about electronics and wish to service the radio yourself, be my guest. Antique electronics can be a fascinating and rewarding hobby -- but be sure you know what you’re doing. There is up to 250 volts inside – enough to light up your life if your fingers are in the wrong place. Also, if bench-testing a radio, bear in mind that you’ll need a good fat power supply to drive it. A typical 6-volt radio draws 8 amperes – and that’s not a misprint! The 12 volt versions draw between 3 and 4 amps – more manageable, but still on the hefty side. I’m sure some of you remember as kids – you listened to Elvis in your parents’ parked car and ended up with a dead battery – indeed with 6 volts you can kill it in less than an hour. For bench testing you can use a car battery if you’re careful, but DON’T use a battery charger – these provide considerably higher voltage than the battery, and can damage the radio. If you want service literature for your radio it’s not hard to find – there are books by John F. Rider (prewar) and Howard W. Sams (postwar) that contain schematics to these radios. Many schematics can be found online, and the complete Riders set is available new on CD-ROM. Common parts such as capacitors are available at electronics parts stores or mail-order houses. However, as I said, unless you want to be a radio hobbyist, better to have it done by a professional.
A couple more things to note about these radios: after World War II, most antennas are similar and interchangeable. Before the war, antennas varied greatly from one vehicle to another. Some were mounted in the fabric top, some were in the running board, some were underneath the car, and there were even some built into the radiator cap! These were very different electrically, and often-required component changes to the radio itself if you were to say, replace a top antenna with a running board type. If the changes aren’t made, the radio will be totally silent unless you’re across the street from a 100,000-watt station! As a rule of thumb, if the radio uses a Motorola connector (the familiar push-in type) it will work with a standard antenna (but don’t forget to adjust the trimmer – more on that in a later installment). If it has a bayonet connector, screw-on connector or some kind of multi-pin jack, it’s best to use the same antenna that came with the car – or an identical replacement. Also, vibrators had a tendency to interfere with reception, so these radios generally had the power supply partitioned off from the rest of the radio. In many cases the power supply was a separate unit. Be aware of this when shopping for an original radio at a swap meet – make sure you’re not buying only half the radio!
This is probably as good a place as any to stop. Next month we’ll discuss the newer radios; hybrid and transistor types. >From there we’ll proceed to stereos, tape players, discuss some tips for checking or shopping for a radio, and then continue on to the modern sets. Until then, enjoy your cruiser and be safe.
http://www.taymanelectrical.com
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