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Mac's Service Shop: Servicing Amateur Equipment
July 1959 Electronics World

July 1959 Electronics World

July 1959 Electronics World Cover - RF Cafe Table of Contents 

Wax nostalgic about and learn from the history of early electronics. See articles from Electronics World, published May 1959 - December 1971. All copyrights hereby acknowledged.

According to sources I can find, it wasn't until the early 1970s that most (>50%) of homes in America had air conditioning. Many home on my boyhood street, including ours, didn't get their first window unit until the late 1960s. We suffered through some pretty miserable hot, humid summers just a few blocks from the Chesapeake Bay in Annapolis, Maryland. Going into stores - especially grocery stores, was a great relief from the oppressive heat. The A&P frozen foods aisle, with the open freezers, was my favorite spot. It's kind of gross, in retrospect, to imagine all the sweat that dripped off people and onto the icy packages lying in the freezers. Electronics service shops of the era definitely required air conditioning to keep all the vacuum tube TVs and radios cool while troubleshooting and aligning them. Of course most of the units would be going back into homes with no air conditioning, so maybe the final alignments should have been performed in a room sans AC.

Mac's Service Shop: Servicing Amateur Equipment

Mac's Service Shop: Servicing Amateur Equipment, July 1959 Electronics World - RF CafeBy John T. Frye

It was hot, steaming hot, outside; and Barney was glad to step into the dry coolness of the air-conditioned service shop. He stood in the doorway for a minute wiping the sweat from his freckled face as he exchanged glances with Mac, his employer; then he turned around, bent over with his hands resting on his knees, and said over his shoulder:

"Boss, would you mind giving me a good swift kick?"

"Don't tempt me!" Mac exclaimed; "but why?"

"I pulled a real boo-boo on that service call I just finished. As you know I was returning a TV chassis I had pulled and brought into the shop for complete re-alignment. It belongs to an elderly couple and the man is very hard of hearing. He uses an earphone connected to the speaker with the wires running beneath the rug over to his chair. He was sitting in this chair when I went in, but he didn't say anything except to nod.

"I explained to his wife what we had done to the set as I slid the chassis into the cabinet and hooked things up. Before putting on the back I plugged in a cheater cord and turned the set on. Everything was fine except for one thing: there was the darndest loudest 60-cycle hum you ever heard. It actually shook the floor! I glanced up at the old gentleman. He was sitting there with the earphone in his ear and a pleased smile on his face. Obviously he was hearing nothing wrong. Maybe he was deaf to the low frequency.

" 'Don't you notice that loud hum?' I asked the woman."

" 'Why, no; I don't hear anything unusual,' she said."

"Was it possible the hum had been in that set so long she had become accustomed to it? Nope, I couldn't sail for that. I know a speaker without a cabinet baffle can't do justice to a 60-cycle frequency; but we couldn't have overlooked a hum that loud. It must be moving the speaker cone a quarter of an inch, I thought. Something must have happened between the time I turned the set off in the shop and the time I turned it on in the house.

"Turning the volume up and down had no effect. Neither did changing channels. All the tubes were tight in their sockets. I pulled the first audio tube. No difference. All the filter capacitors must be wide-open. Reluctantly I decided the chassis had to come out again, and I reached around and turned the set off. The hum didn't stop! In desperation I jerked off the cheater cord. The hum kept right on humming. I really began to believe I had popped my cork.

"At this moment I happened to glance up and saw the old gentleman reach around behind his chair and pull a cord out of a wall socket. Instantly the hum ceased. Following that cord with my eyes, I saw it went to a little cushion on which his feet were resting. It was one of those vibrator pillows. No wonder my 'hum' had been shaking the floor!"

Mac chuckled aloud as Barney finished the story. "I'll bet you really felt silly," he chortled.

"Well," Barney answered, grinning at the memory, "all three of us had a good laugh when I explained what had been bothering me. They were so used to the humming of that vibrator pillow they didn't notice it at all. Did anything interesting happen while I was out?"

"A kid was in here trying to get me to work on his ham transmitter. I told him we didn't do that sort of work in the shop but that possibly you might help him out on your own. Here's his address and call."

"Yep, I know him," Barney said as he glanced at the slip of paper. "He's only had his Novice call a couple of months. You know something? Getting ham equipment repaired is becoming quite a thing."

"How come?"

"In the old days practically all amateurs built their own equipment, both receivers and transmitters. When they designed, built, and spent several weeks de-bugging their rigs, they were in an excellent position to take care of any trouble that popped up later. Today we have a whole new breed of hams. Practically none of them build their own receivers and an increasing number don't even build their transmitters. As soon as they get their license they go down to the store and buy a complete station. All they have to do is connect the receiver and transmitter up to the antenna and plug in the key or mike and they're in business. All goes well until something conks out in the equipment. Then they feel as helpless as if they had to depend on themselves to repair their TV set or their watch."

"But a ham's got to pass an examination on transmitter and receiver theory to get his license."

"True, but you're the last one I need to tell there's a lot of difference between having an elementary grasp of radio theory and possessing the practical experience and confidence needed to tackle a sick communications receiver or complex modern transmitter."

"Hm-m-m-m, I see what you mean.

On the other hand, the average radio and TV service technician isn't prepared to take on the job. He, too, lacks experience with high-powered transmitters. There's a lot of difference between working with r.f. circuits handling only microwatts of power and working on a transmitter in which a tube's grid circuit is likely to be handling more power than the plate circuits of receiving tubes. The service technician has had only limited experience with tubes operating in class C or class B. The TV technician is accustomed to working around high voltage, but he is not eager to mess with the lethal combination of high voltage and high current found in transmitters.

"Having no license himself, he can't make on-the-air tests without the owner present. Ordinarily he will have no transmitting antenna available at the shop. He is unable to fall back on one of his most trusted servicing techniques: the substitution of parts known to be good for doubtful parts. How many service shops have a stock of transmitting tubes, high-voltage filter capacitors, or modulation transformers?

"Finally, there's the matter of charging for the work. Remember the service technician is in business to make money, not to amuse himself. His time at work must bring in a calculated return if he is to stay in business. If he charges his regular rate for the time he must spend 'boning up' on the particular transmitter to be repaired, the owner will quite likely have a whopping big bill. On the other hand, the service technician can't afford to charge less than he could make working at his specialty: receiver service. Keep in mind it's not to his discredit that he knows little of transmitter circuits. He is a specialist in radio and TV service. Even a superb brain surgeon would probably want to do a little studying before attempting to deliver a baby!

"How about the ham's returning the transmitter to the manufacturer? There they should have the required knowledge, testing facilities, and replacement parts."

"That's a good last resort, but it has some drawbacks," Barney answered. "For one thing, trying to crate a heavy, delicate transmitter so it can be shipped without damage is about as easy as trying to wrap up a scythe in a newspaper. Even after the transmitter has been repaired it still has to make the rough trip home and it's quite likely to develop some new troubles as a result of this shaking up. Moreover, factory service is notoriously slow; and the average ham can't bear to be without his rig a day longer than necessary."

"OK, then; what's your answer to the problem?"

"I'm old-fashioned enough to think the best answer is still for the ham to educate himself to repair his own rig. Acquiring the knowledge of what's going on inside the equipment is a very large part of the fun of hamming. The guy who only operates misses all this. And really it is not too hard. Even the most complicated transmitter is simple, circuit-wise, when compared to a TV receiver."

"That's right. If the new ham would sit down as soon as he buys his transmitter and puzzle out the function of every part shown on the diagram, he'd be off to a running start. Once he knew what every part was supposed to do, he could consider the symptoms and make a shrewd guess as to which one had fallen down on the job."

"Check! Another thing he can do is keep a notebook of the comments he hears about his rig on the air. Every time he hears a fellow ham talking about trouble, its cause, and the cure with that particular transmitter, he should write it down. Each model transmitter has certain weak points that fail in unit after unit, just as is the case with TV receivers. That notebook can be a real help when trouble comes."

"Of course," Mac added, "he'll need some test equipment - at least a good v.o.m."

"Sure, and he should use it to do his darndest to find the difficulty himself. However, when he can't do it, he should next hunt up another ham with lots of experience and know-how. Many of these old-timers or just plain sharp boys are scattered around over the country. They are invariably willing to help a fellow ham who is really stumped, but they don't like having the problem just dumped in their laps without the owner's trying to help himself. These outstanding hams are almost sure to have good test equipment and access to substitute parts; but far more important they have a command of theory and a wealth of experience to help them. The new ham who can make a friend of one of these has a great treasure, and he will be wise not to abuse the friendship by asking for help with things he can do for himself."

"Amen!" Mac agreed heartily.



Posted August 3, 2018

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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