Please click on the picture. This is the way service personnel learned about Betamax, through factory instruction manuals and tapes used during classes taught by Sony field professionals. Training was constantly needed to keep technicians up to speed about circuit designs, production changes and new features.
Early on Sony knew that to keep the Beta format reliable was going to require training, factory training. Eventually Sony would take on the full responsibility of service and repair of most of their products, because they wanted the quality control that it allowed them and they wanted the revenue. Many independent service people saw this as kind of a slap in the face, a statement that they were somehow not qualified to work on Sony's newest products. Suffice it to say that it didn't win Sony any Betamax supporters from the repair industry. Especially since VHS was easier to work on, required less professional skill and they didn't care who worked on them (and VHS was outselling Beta anyway). It's hard to say which came first the chicken or the egg but the reality of it was many technicians did simply lacked the desire to work on Beta and many began to refuse to repair them altogether, something that also didn't help encourage people to adopt Beta.
I doubt that you, the reader, are preparing to work on a Betamax. But you may be interested in how sound and video is stored on tape and then played back. So in this panel we are going to take the information contained in those training manuals and make it easy to understand. Trust me. It'll be simple and fun, so let's get started. Click on the picture. If you started at the beginning of this "Legendary Betamax" section you've already been through the discussion on how conversion is needed for recording so you're ahead of the game. If you haven't done so you can go back to the very first panel, but here's a quick look at what was covered. Examine the picture above. In the center we see the human brain. On the left is an ear and on the right is a eye, sound and sight. Both of these specialized organs have been designed by nature to take mechanical forces and convert them into electrical signals, because the brain is an electrically operated central processor. In the ear the vibrations from sounds hit the drum and causes it to move. This mechanical movement is passed along to a special organ that has tiny hairs inside it that has a nerve(s) attached to each hair. When they wiggle the nerve sends an electrical signal to the brain that processes it and interprets it as sound. The eye is very similar. A wave particle of light enters and strikes a special receptor in the back of the eye. This generates an electrical charge, which goes to the brain and is constructed into an image. So on the most basic level we are constantly converting information around us into electrical information that our brains can process. Conversion isn't new and without it many things simply wouldn't work.
But all of these methods involve a process of conversion. It is very close to the magnetic rod but doesn't touch it, it is free to move. Click the picture again. Here are some common ways conversion is used for recording and storing information. It sounds silly to say this but if you waved an audio tape or video cassette in front of your TV all that would happen is your arm would get tired. The tape itself would not be affected. To make a recording requires an instrument that changes the video and sound into something the tape is made to store. To playing it back simply reverses the storage process. The Betamax is just such an instrument. Click the picture.
Here is the video recording conversion process in simple terms. At the moment it may look complicated but I assure you that it is not. Your guarantee that it is not difficult to understand is proved by the fact that we humans developed this system. We use it all the time and knowing how it is supposed to operate gives us the ability to fix it if something goes wrong. So here we go, as I said understanding audio/video recording and the Betamax is simple, I assure you. Audio recording is easiest that is why it is at the top of the list, so we'll do it first.
Click the picture. To get sound onto tape we have to change it. Look at this simple diagram of a public address system. On the upper left in the picture is what is simply a mechanical ear, a microphone. It has a flexible diaphragm made of a thin material, usually shaped like a disk or dinner plate. It is shown at the lower left. Attached to the diaphragm is a coil of wire that is free to move back and forth when the diaphram is hit by a sound vibration. The coil floats around a round rod shaped permanent magnet, but it doesn't touch it. When sound vibrations hit the diaphragm it vibrates. More when the sound is loud, less when it is soft. This also moves the coil around the magnet and this generates a small amount of electricity. Physical fact: moving a coil of wire over a magnet will make electricity. Good thing too, otherwise most of our electrical power would come from chemical reactions which could be dangerous and messy. The electricity coming from the moving coil is very weak, but we can amplify it, as shown in the center of the picture above. After we do this we can send the amplified (stronger) electricity to another device that will reproduce the sound. Called a speaker, shown on the right, it is very much like a microphone (shouldn't it be called a listener?) except it can handle move electricity. It has a moveable diaphragm with a coil of wire attached to it and a permanent magnet just like the microphone, all of it on a larger scale. Another physical fact: exciting a coil of wire wound around a permanent magnet with electricity will generate more magnetism. If the coil of wire can float it will make the diaphragm move and this will generate sound. So what we end up with is sound in, amplified, more sound out. Let's do one more thing to this sound. Let's find a way to store it so we can use it over and over again.
Click the picture. Let's store the sound on magnetic tape. Stay with me now because once you get through this magnetic recording process you've got it whipped. Everything from here on is just variations on a theme, simple stuff. That same electricity that moves the coil in the speaker can also be used to create a magnetic field for recording onto tape. In the picture above we see two electromagnets (greatly enlarged). When electricity is passed through coil of wire wound on the one on the left (recording head) it makes a strong magnetic force (called a field) where the gap is located (shown by the white radiating circles). If a strip of iron coated tape is passed along next to this force it will become magnetized. Pass it by at a uniform speed and a magnetic image can be imprinted (recorded) onto the tape that duplicates the electrical force (sound) that is energizing the field. The sound has been stored as scattered iron particles (little magnets) on the tape. (This is all on a microscopic size.) To get the sound back from the tape is just as easy. Just rewind the tape and send it by another electromagnet, shown as the one on the right. This time the head will be passive or said another way, it will be used to receive the stored magnetism on the tape. This electromagnet is just like the other one (it can even be the same one) but it will be used in reverse (playback head). The tiny magnetized particles on the tape made during the recording process will generate a field that makes electricity in the coils of the wire wrapped around it. Amplify this and you get the sound back. This is almost exactly how the audio is recorded and played back on the monaural track of a video recorder. And quess what? Video is recorded almost the same way so it's smooth sailing from here on out. Now on to video.
There's already a couple a things you already know about recording video. The first thing is we're going to use magnetic tape to do it, so the same physical principles are involved in the recording process. And second the video must somehow be different because we're discussing it seperately from audio. Right on both counts. So let's concentrate on that second point, why video is different. Keep in mind we are still going to use electromagnets changing iron particles on a long ribbon of tape. But it is these iron particles that forces us to use a slightly altered method for recording video. It has to do with their physical limits. It is just not reasonable to try and cram all the information necessary to record video onto a given section of tape (more on why that is in a moment). This is an important point so let's go back briefly and take another look at audio recording. As we have seen it's simple. When the magnetism generated by the electricity coming from the amplifier changes the iron particles on the tape (magnetizes them) it is done in pulses. Imagine these like the waves or ripples you get when you throw a rock into a still pond. The big slow ripples would represent the low pitch sounds and the tight fast ripples the high pitch sounds. The low sounds record easy because their big but the higher ones can get close together and that can be a problem. If they get too tightly packed they run together and become one big pile of noise. The solution to this problem is to speed the tape up. This speads or stretches the magnetic waves out over a longer distance making the highs more defined. The faster speed allows higher sounds to be recorded with no loss of the lower ones. A common speed in studio tape audio recording is 15 inches per second. Compromises are made for economy in home reel-to-reel recorders, they usually record at 7 1/2 and 3/3/4 ips. There are slower speed recordings of 1 7/8 and 15/16 ips. but they require special compression technology to reduce tape noise and to capture the highs, but this isn't really relevant to our discussion. Back to video. The challenge video presents to magnetic tape recording is that the waves or frequency (a word that means how many in a given time) are so high that it is beyond the capability of the particles on the tape. Yes, you could run the tape really fast but this gets messy. High speed recording increases wear and generates a lot of heat which can destroy the recording head. Also, serious damage can occur if something goes out of control. These are unnecessary risks since there is a easy and clever way to get around the tape limitation issue.
Up until now all we have discussed has been recording using stationary heads, ones that are mounted solidily to the recording platform. To get the faster speeds necessary for the higher frequencies needed for video recording the answer is to spin the recording electromagnets. This is accomplished by actually mounting the recording head on a disc or drum (called a scanner) then wrapping the tape around it. Click picture. Two types of video drum rotations are shown. The top one requires wide tape to work so it was only used in professional broadcasting. In the bottom design the tape doesn't have to be so wide, this one is the most common. Using the scanner system allows reasonable tape travel speeds because the spinning head(s) provide the needed recording distance and speed for recording the higher frequencies demands of video. With the longitudinal system the tape is slanted slightly as it travels around the drum so that each scan or head rotation is slightly behind the one before it.
So now we have the high frequencies stretched across a long track on the tape so video can be recorded. There is a little more to this. Everything has to be timed just right, which requires some precise motor operation. And the recording information has to be converted to magnetic pulses, but that's it. We have a video recorder. So next we are going to examine how the motors are controlled and how the video and audio is processed. To go to the that discussion click here.
Want a break? Listed below are several related subjects that you may want to check out. You will be given the option in each of the panels you open to return to this page or go forward to the section on motor control and video and audio operation.
If you would you like to skip this section altogether and go forward on to the next subject panel "Innovative Betamax" click here.