Mac's Radio Service Shop: Thoughts on Test Equipment |
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When reading through this "Thoughts on Test Equipment" episode of John T. Frye's "Mac's Radio Service Shop" is seems maybe he was describing what would become two decades later the Betamax (aka Beta) analog audio-visual (A/V) recording and playback system. Mr. Frye incorporated that sort of visionary thinking in many of his stories. Here, Mac McGregor was experimenting with recording "real" television signals on high fidelity audio tape and then using it later during troubleshooting and alignment of sets in his shop. The idea was born out of a lament about how specialized and expensive service test equipment had become as new and more sophisticated radio, TVs, record players, tape decks, etc., were coming onto the commercial marketplace. Says Mac, "We've reached the point where our service instruments are more expensive, more complicated, more subject to trouble, and harder to learn to use than the apparatus upon which we work." That reality is part of the reason so many of the products on the market have evolved to where the price of manufacturing and distribution makes paying someone to troubleshoot and repair them often is greater than just throwing out the broken item and buying a new one. Assemblies are so modularized now that there are not that many separate failure-prone parts anyway. My own experience with troubleshooting newer items it that often the cause of failure is a contaminated or loose interconnect cable within. They are the most vulnerable points in the circuits. I have restored an amazing of number of TVs, radios, toys, computers, appliances, and other things for myself, friends and relatives simply by disconnecting and reconnecting all the connector interfaces. Try it the next time something goes on the blink and it's not due to some other obvious cause. Mac's Radio Service Shop: Thoughts on Test Equipment
Mac had come down to his service shop this warm July evening to tryout some new test records and a test tape he had just received. While he was busy running the signal-to-noise checking portion of the test tape through the recorder, he heard the front door open and bang shut. "Ha!" came the accusing voice of Barney, his assistant, as the youth strode through the door of the service department. "You trying to put something over on me? What's the idea of sneaking down here after hours? What're you holding out on me?" "Now calm yourself, Buster, before you melt a connection," Mac said soothingly. "It just happened these records and tapes came in late this afternoon after you had gone home, and I was eager to try them out at a time when I would not be interrupted - I hoped," he added pointedly. "You could have let me know," Barney grumbled. "I saw a weather forecast for heavy thunderstorms for tonight, and I came down to be sure I had pulled the master bench switch. Gosh," he broke off, as his eye caught sight of a stack of red, yellow, green, and blue, 5- and 7-inch plastic reels, on two of which were wound rolls of green and blue plastic tape, "are those the test tapes?" "Nope. Those are just some of the new colored reels and tapes recently put on the market. I'm going to try and work out a color-code scheme for filing our recordings that will let us know at a glance if a particular reel of tape is important not-to-be-erased material, is recorded from the microphone or by direct pickup, or if it contains blank tape, etc. Since we have five colors of reels, including the transparent, and three colors of tape, counting the conventional brown, the possibilities are considerable, and I want to work out a system that is simple and easy to remember but that will allow us to file our tapes under many color-keyed listings. "The test tape is on this five-inch reel," he said. "It and those test records over there are the ones we read about in that article in the May issue of Radio & Television News as being released by the Dubbings Company." "Say, you're really becoming pretty loopy about this tape business, aren't you?" Barney asked quizzically. "Couldn't you change 'loopy' to 'interested' ?" Mac asked. "I'll confess I'm greatly intrigued by the possibilities of tape recording, especially now that it is possible to record light images and other information on tape as well as sound. I keep thinking that possibly there is something here that will solve a problem that is beginning to be a big one." "What's your problem?" Barney wanted to know. "It's not just my problem; it's the growing problem of every service technician. In brief, it seems to me that the test equipment situation is getting somewhat out of hand. We've reached the point where our service instruments are more expensive, more complicated, more subject to trouble, and harder to learn to use than the apparatus upon which we work. If things keep on at the present rate, it does not take too great a stretch of the imagination to picture a time soon when the technician will be so busy studying and selecting new service equipment, learning how to use it, and keeping it in repair that he will not have any time left over at all for doing service work." Barney grinned broadly at this picture. "Guess it is not too far-fetched at that," he conceded. "The other day I counted up a total of sixty some tubes that are in use in just our test equipment. Sixty tubes and their associated circuits represent a lot of room for trouble. Much of that equipment, too, must or should be constantly checked to be certain it is operating as it ought to. As a 'ferinstance,' we do not depend upon the calibration of the sweep generator but use our marker generator to indicate exact frequencies; then we do not rely on the accuracy of the marker generator but check it against a crystal oscillator; and finally, we do not take the crystal oscillator frequency for granted but check it against WWV. Sounds kind of wacky, doesn't it?" "Sure does," Mac agreed, "and that's only one example. The increasing number of articles we see in service magazines on how to check, how to maintain, and how to use the many, many service instruments considered essential for present-day radio and TV servicing is a key to how serious this state of affairs is becoming. You've got to keep in mind that all thought and energy expended on service instruments is so much lost motion as far as direct addition to your income is concerned. When you are studying and working on service instruments, you could be working on a radio or TV set and being paid for doing so." "But if you really know your service instruments and if you keep them in good shape, you can do more and faster service work," Barney argued. "I'm not disputing that," Mac explained; "but what I am trying to say is that anything that takes your attention away from the essential job of repairing sets cuts into your income. Service technicians are constantly being told they should become better businessmen, which is another way of saying they should evaluate all their procedures strictly according to whether or not these activities increase their net income. Up to a point, time and money spent on service equipment will still yield an increased income in spite of the fact that the money is subtracted and the time is diverted from the service business proper. Eventually, though, the law of diminishing returns whittles down this increase until it no longer exists. I'm thinking that point is not too far away." "What can be done about it?" "Candidly, I'm not sure anything can; but I've some ideas I'd like to see tried. Manufacturers could help a lot if they would prepare service instructions with an eye to the equipment found on a typical service bench rather than the instruments on hand in their own engineering laboratories. I don't mean they should try to write up this service data so that everything can be done with a v.o.m.; but at the same time I feel that service instructions calling for special high-gain, broad-band oscilloscopes, sound and video crystal markers for every channel, etc., is pretty well wasted on the average technician. Far too much of this manufacturer-prepared service information sounds as though it were written to impress a competitor's engineering staff rather than to aid the technician." "Maybe we ought to have some kind of standardization of service instruments," Barney suggested. "That would be a good idea if it could be worked out. For example, if various service instrument manufacturers and set manufacturers could get together and decide what instruments are essential for modern service work and what minimum specifications for those instruments should be, that would be an excellent first step. Then service instructions could be prepared around these standardized instruments. Furthermore, a technician buying a piece of test equipment would only need to compare the specifications of the instrument being considered with the standard specifications to know whether or not he could rely on it to do the job. "He does not know that now. I was reading a couple of months back where an experimenter checked six different commercial sweep generators and found only one make had sufficiently good linearity, flat response, and adequate sweep to warrant its use without making allowance for errors - and that one cost over four hundred dollars! In using the other five, the technician had first to identify the shortcomings of the particular instrument and then to take these peculiarities into account in observing every trace produced with it. That's like trying to hunt with a rifle that shoots several degrees to the left of where the sights point. You may be able to do it, after a fashion, but it'll not be easy." "What's all that to do with test tapes?" Barney demanded. "Keep your shirt on; I'm coming to that," Mac retorted. "I keep thinking that what is really needed in TV service is a signal generator that will produce a real honest-to-gosh TV signal in the same way our AM signal generator produces an actual radio signal. Now that a complete television program can be recorded in black and white or color on a single tape, I believe we are in striking distance of this ideal. First. we shall need a couple of oscillators representing video and audio carriers whose frequencies can be adjusted to the carrier frequencies of any channel. Then the video oscillator will be AM modulated with the picture information on the tape and the audio oscillator will be FM modulated with the tape's audio track. The output of the oscillators will be combined, controlled, and fed to the antenna terminals of the TV set being tested. "The picture information on the tape can contain any type of information needed for testing. In fact, just a standard test pattern would provide a wealth of information; but other portions of the tape could produce patterns such as are normally obtained from a cross-hatch generator, a dot generator, or a color bar generator. Picture information could be entirely removed and just the sync signals observed. The output of the generator could be attenuated from a maximum to a strength such as would represent the weakest fringe-area reception." "You don't think that kind of an instrument would be cheap, do you?" "No, but I'm sure it would replace several other instruments now used whose total price would more than equal its cost. Still more important, a technician using such an instrument could determine in a few minutes more information about the condition of a receiver under test than he would be likely to learn in several hours of probing with conventional test equipment. I'm not saying we ought to have cheaper equipment. My argument is that we should have fewer and better instruments that will tell us more in less time. The way it is now, all the manufacturers seem to be trying to do is to load us down with more and more test equipment. As it is, we've had to put sideboards on our service bench to accommodate this equipment, and the end is not in sight." "Somebody is always spoiling things," Barney complained. "I was just planning on setting up in business as a test equipment technician, and I had already worked out a fine business motto: 'Brainy Barney, the Servic-man's Serviceman.' "
Posted July 14, 2020 Mac's Radio Service Shop Episodes on RF Cafe This series of instructive technodrama™ stories was the brainchild of none other than John T. Frye, creator of the Carl and Jerry series that ran in Popular Electronics for many years. "Mac's Radio Service Shop" began life in April 1948 in Radio News magazine (which later became Radio & Television News, then Electronics World), and changed its name to simply "Mac's Service Shop" until the final episode was published in a 1977 Popular Electronics magazine. "Mac" is electronics repair shop owner Mac McGregor, and Barney Jameson his his eager, if not somewhat naive, technician assistant. "Lessons" are taught in story format with dialogs between Mac and Barney.
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