An Old School Education – Radio & Electronics Course 1B: “Parts is Parts!” Hear No RF Evil - See No RF Evil |  |
| An Old School Education – Radio & Electronics Course 1B: “Parts is Parts!” Posted: 17 Sep 2012 08:39 AM PDT The year is 1960, and the young Curmudgeon-to-be, still a university student, is working part-time as a counter clerk in a general electronics store and is simultaneously soaking up an "old school education" from his work experiences there. The parts side of the business was more interesting and more educational for me than were the consumer sales. Having independently studied electronics during the previous year with the goal of earning an Amateur radio license, I had "book-learned" mostly just the fundamentals. Now I could deal with actual parts and circuits, and with the people who bought and used those parts. Independent commercial radio/TV repairmen were the major parts customers, although the occasional hobbyist or ham did come through the store. The TV guys (I never met any female techs) were a crusty bunch. They usually didn't have much formal education, often having learned electronics repair in the military or as apprentices to older guys. Most of their diagnostic and servicing knowledge was at the practical rather than the circuit analysis level. Thus their conventional knowledge: "If the picture tube shows no sweep, just replace the sand-covered, 10 watt-rated, power resistor connected to the cathode pin of the horizontal output tube; it's blown." As a group they didn't make much money and they had to scramble to keep moving and to get enough work to support their businesses. Thus in dealing with them this young salesman learned customer service skills quickly. These guys didn't have time to waste, and they didn't have much regard for the young clerk who thought electronics was "the neatest thing since sliced Coors in cans!" Electronics was just their "pork and beans," and there was nothing at all romantic about that.  Vintage 1950's Radio-TV Repair Shop The major consumer electronics products of that time were intended to be fairly inexpensively repaired if they quit working, since products of those days did not have the inherent reliability that is common today. No consumer would ever think of just discarding a relatively new TV set that had failed; it would be repaired and returned to service, period. Much of the repairmen's trade was "tube swaps" in the customers' homes, and the men traveled with well-stocked tube caddies. But some TV sets did develop fried under-chassis components, and these sets went back with the repairmen to their shops. So the repairmen would come into the store with lists of parts needed for current bench jobs, or items necessary for new rooftop antenna installations, or to refill their tube caddies. They typically needed three different categories of supplies. The first category was vacuum tubes. In those days we did not sell many semiconductor parts. Commercially, transistors and solid-state diode parts had been on the market for only a few years and they were expensive. A "cheap" experimental transistor, the Raytheon CK-722 germanium point-contact small signal amplifier, cost the equivalent of $10 (in 2012 terms). It was so low in performance that today no one would consider using this device for any purpose. So there was not much call for replacement transistors for repair work.  Vacuum Tubes in All Shapes and Sizes Were Used in 1960 In vacuum tubes we stocked probably two hundred replacement types, and they formed the basis for a lively trade. Some types were absolutely "standard," and I quickly learned these types and their prices. A 6AL5 was a 75 cent dual-diode FM detector, almost universally found in TV and FM receivers. A 5U4GB was always the power rectifier in TV sets, and it cost $0.95 in 1960 dollars. Type 6SN7 was the sweep oscillator and 6DQ6 was often the horizontal output tube in TV sets, 6L6s (with a metal tube envelope) and 6L6GTs (with a glass envelope) were often audio output tubes in stereo amplifiers, etc. We mostly stocked tubes made by Tung-Sol (a well regarded company, which is now long departed) but we also sold GE and RCA tubes. There was also a continuing trade in a different kind of vacuum tube: rebuilt CRT picture tubes. We stocked a good supply of these in large sealed cardboard cartons in the store's rear storage area, and often I would have to dig for one to meet a repairman's request. It wasn't easy, moving all the stock around to locate the right one. These "rebuilts" sold for half the price of a brand new tube or even less, and everybody installed them as replacements. In reality, the only part of the CRT that was re-used was the thick glass envelope; all the internal parts were new. We sold only black and white CRTs of course; it was too early in the game for replacement color picture tubes. Replacing a CRT wasn't a particularly difficult job; I once did it successfully on my own TV. One needed only to remember to keep his fingers well away from the 25 kV anode connection on the glass envelope of the old picture tube, lest a memorable "bite" be delivered from that HV point. The HV potential, even in a "dead" picture tube, resulted from charge being stored in the inherent distributed capacitance in the tube's physical structure. Second, the TV guys needed published service information for the sets on which they were working. In those days the needed information didn't come from the TV set manufacturer, although with some effort it might have been obtained there. Rather, it was provided by the Howard W. Sams Corporation, in monthly "magazines" known as Sams PhotoFacts. Each monthly issue contained service "folders" for about six or so new television receiver models, in an assortment from all the major manufacturers. Each of the individual folders contained all the information necessary for working on one particular chassis (or a few closely-related ones): complete schematics, voltage and resistance maps, parts lists, alignment instructions, tips, etc. Some of the larger repair shops routinely purchased each month's magazine as it was issued and they kept all of them in file cabinets. Smaller shops bought from us just what they needed for the current work. The price for a month's magazine was $2.95, not a small amount!  Industry Repair Bible – Sam's PhotoFacts Third, the repair guys needed passive electronic parts. Parts could be resistors and pots (generally IRC and Ohmite), switches and capacitors (Centralab), coils, signal transformers, RF chokes, and inductors (J. W. Miller). All these companies were "American standards" in the parts business of the time. Or they might be power transformers (Thordarson-Meissner or UTC). Vacuum tube equipment drew considerable primary electrical power (relative to today's solid-state gadgets) and required high voltages (200 to 500 volts d.c.). No "regulated 12 volt buss supplies" were used in that world. Almost every device of significance used a power transformer which would heat and occasionally short out, and replacements were needed. TV sets also used a "flyback transformer" to produce the 25 kV potential for the anode of the picture tube from the horizontal sweep amplifier, and these required frequent replacement also. So in doing this work I learned to deal with many different types of customers. There was the repair guy who used one of the first artificial larynxes I had ever encountered in a human. Apparently he had "smoked out" his original larynx. He had a primitive battery-operated vibrator which he held up to his Adam's apple while he spoke. It produced a weird, robot-like, monotone speech pattern that was a bit difficult to understand, but he got his parts as quickly as I could move. And then there was the fellow who once routinely asked for a "300 ohm (twin-lead), 20 dB pad," a fixed-attenuator to be inserted into the TV/FM antenna's flat ribbon transmission line. Based on my (then) "half-vast" knowledge of the parts business, I quite confidently assured him that "there is no such device," and thus we certainly wouldn't have one. His response was simple and direct: "Out of my way, son!" He stomped past me over to the Centralab parts cabinet sitting in the shelves behind the counter and in a split-second he fished such a pad out of it. I sheepishly wrote up the order. And that's how my old school learning, the kind of learning that was nowhere to be found at the university, progressed over the course of the months. Well, this education couldn't go on forever, and it didn't. After about a year of this, my bride informed me that she was tired of sitting home alone all weekend, and that I had better find other work. She was correct of course (when was she ever wrong?), and so I bade farewell to my dream job and moved on. I picked up enough other part-time work to get us through to our graduations, after which I moved into full-time industrial science and engineering. A few weeks ago I was back in that city of my youth and, for nostalgia's sake, I cruised past the old store. Yes, the building is still there (it's now a retail unfinished furniture shop), but my bosses Mike and Erv and the business itself are long since gone. After that wonderful experience I would never again work that special kind of job, but I treasured the fact that I once had the chance to do it. Only for a very few, very brief periods in my later career would I experience anything even remotely close to it again. The fact that this kind of old school education is no longer available in today's world is a real loss. New engineers are somewhat limited if they did not get that kind of learning. So, about forty years after leaving the old school I was the engineering representative on a small panel conducting a job interview for a candidate B.S.E.E to join our project. I had earlier read the candidate's resume and knew that his professional engineering experience and university education were solid. And I also knew that a job offer awaited him; the interview was just a formality. But I had to ask him some sort of question during the session.  Venerable Resistor Color Code – In Use Since 1920 So I used one of my "default" electronics questions, in an innocent attempt to "toss him a softball" and make him look good before the non-technical managers on our team: "What is the color code for a 4.7K-ohm, ½ watt, 10% tolerance resistor?" (How many of these same devices had I pushed across the counter to the TV repairmen at the old store? To judge from the candidate's response, you would have thought that I had asked him to derive Einstein's Special Theory of Relativity starting from Newton's Laws of Motion! This graduate engineer instantly turned crimson. He wheezed. He gasped. He stammered. "Oh! Er! Ummmm! Mmmm!…..Gee, I can sort of vaguely recall something about Roy G. Biv!" Sputter. Choke. (Long swallow) And then, sheepishly, "Oh, if I could just get to the Internet I know that I could find the answer!!!" (The answer that I hoped for and expected to receive would have been, "yellow-violet-red-silver, of course, and I used a bunch of them when I was building my kilowatt amplifier for the HF ham bands that I designed myself." But alas, it just wasn't to be. There was only sputtering.) "No need to look it up," I said aloud, "you passed. No further questions." And in the same instant that I spoke the above statement, in my mind's eye I could just see those crusty old TV repairmen looking down on the scene and rolling around in the aisles of our long-ago, far-away store, uproariously laughing their fool heads off! They had been my unwitting but exacting "professors" at the "old school," and they had taught me very well indeed, bless 'em all! What do you think? "Let's save the universe for RF!" The Old RF Curmudgeon Since 1963, LBA has been providing RF equipment and engineering consulting services for radio and television broadcast and wireless communications. The post An Old School Education – Radio & Electronics Course 1B: "Parts is Parts!" appeared first on LBA Blogs.    |
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