Summer begins this week in the
northern hemisphere, and winter begins south of the equator. Counterintuitive to
northerners not familiar with the geometric cause of seasons (axis tilt) is that
the Earth is actually closest to the sun in January than it is in July. Our orbital
path is nearly circular, with an
eccentricity of just 0.0167. Anyway, I thought the onset of summer
would be a good time to post this installment of Mac's Radio Service Shop entitled,
"Summer Seminar." Typical of author John Frye's techno-sagas, more than one theme
runs through the story. It begins with shop owner Mac admonishing technician Barney
for throwing away a faulty
when he knows there is an industry-wide shortage on supplies of the element and
the bad components should be submitted for recycling. Fretting over as common an
element as selenium might seems ridiculous in these times of plenty, but resources
were more difficult to come by at the time. Prospecting for, extracting, and processing
just about every element in the periodic
table is almost a boring exercise. However, with the rate at which elements
are consumed in the manufacturing of such a vast amount of products as are used
nowadays, some scarcity is being reported in the news. Helium, the second most abundant
element in the universe, has been mentioned. Yttrium (used in oscillators) and neodymium
(super magnets) supplies are now being threatened by trade wars. Others have been
identified as well. The threat of scarcity is not for lack of known deposits but
because of poor planning on the part of nations that have knowingly risked their
own sovereignty and independence by facilitating - even directing - the concentration
of production exclusively offshore while eliminating domestic capacity for production.
In the case of the U.S., the resources needed to protect our economy and freedom
can be mined within its borders, but it will require immediate commencement of production
Mac's Radio Service Shop: Summer Seminar
By John T. Frye
The soft little breeze drifting through the wide open doors of the service shop
felt good to Mac and his helper, Barney, as they worked away at the bench on this
warm June afternoon. Mac glanced up from the new TV tuner he was installing in time
to see Barney toss a selenium rectifier he had just removed from a three-way portable
into the trash barrel.
Making sure he had Barney's attention but without saying a word, Mac fished a
dime from his pocket and nonchalantly flipped it into the barrel.
"Hey! You popped your cork?" Barney asked anxiously. "Wasn't that a dime you
just threw into the barrel ?"
"That's right. If you can throw away money so can I."
"What do you mean: I throw away money? My mother never had any stupid children."
"Didn't you just toss a selenium rectifier into the trash barrel?"
"Sure, but it wasn't any good." "Remember my telling you selenium is in short
supply and that rectifier manufacturers have asked us to save old rectifiers so
the selenium can be reclaimed?"
"Yes, now that you mention it, I do recall your saying something about that.
In fact, I also have a hazy recollection that our parts salesman mentioned he would
give us ten cents for every old rectifier we turned in, no matter what the size.
It just sort of slipped my mind."
"Well, just sort of slip into that trash barrel and fish out the rectifier you
tossed in as well as any others you may have discarded when I wasn't looking. And
while you're in there, you may as well recover my dime."
"OK, Boss," Barney said with a broad grin on his freckled face; "and you certainly
made your point. I may forget Ohm's Law or even the color of my Margie's eyes, but
the sight of a Scotsman throwing away money is something I'll never forget."
Fortunately the barrel had been dumped only a day or so before; so recovering
the rectifier and dime was easy. Barney placed the rectifier in a cardboard carton
and facetiously marked the outside "Old Diamonds, Old Gold, Old Selenium Rectifiers,"
Etc." and placed it beneath the bench. Then he turned his attention to what Mac
"Did lightning clobber that tuner?" he wanted to know.
"Yep, and it did such a good job that a complete replacement is the only practical
"Another case in which the lightning arrester obviously fell down on the job,"
Barney offered. "Sometimes I think those things are just a waste of money."
"Lightning arresters are something like kids," Mac said with a tolerant smile.
"People expect more out of them than they can deliver, and they get a lot of blame
they do not deserve. A properly installed lightning arrester with a short direct
lead to a really good ground will do an excellent job of protecting a TV set from
surges induced into the antenna and feedline by nearby lightning strokes, but only
a fool would expect it to furnish protection from a direct stroke to the antenna
itself. Neither will a lightning arrester afford protection against damage by lightning
that is going from the set into the antenna."
"From the set into the antenna!" Barney repeated. "What kind of crazy talk is
"It's not crazy at all. In fact, most of the lightning damage in this area is
caused by surges going up the feedline rather than down it. Keep in mind that the
majority of the antennas around here are of the yagi-inspired type that has the
driven element directly connected to the boom, the boom connects to the mast, the
mast connects to the tower, and the tower is grounded. In other words, the antenna
is actually at ground potential.
"Now let's review what happens when a stroke of lightning sends a surge along
the 'hot' wire of the power line to which the TV set is connected. This surge comes
in on one side of the line cord and promptly goes through the line bypass capacitor,
if one is present, to the chassis. If no capacitor is used between the line and
the chassis, as is often the case, the surge may jump the switch and reach the chassis
by breaking down the insulation between the power transformer primary and the core
or one of the other, grounded windings. Once on the chassis it goes through the
grounded center-tap of the antenna coil connected through the turret switch to the
antenna terminals, up the lead-in to the antenna, and back down the mast and the
tower to the ground, where it had been heading all the time.
"When you look at the charred coil and the melted turret contacting fingers,
there is no way of telling which direction the surge was travelling when it passed
through them. In fact. the natural conclusion to reach would be that the damage
was done by a surge coming down the feedline; but actually the chances are that
it was going up the feedline as I described. Whenever you are checking out a set
with these symptoms, be sure and test for a short-circuit between both sides of
the line cord and the chassis before letting the set out of the shop. It is a good
idea to disconnect the resistor often found between one side of the line and the
chassis while making this test so that a high value of leakage, that can quickly
change to a low value when the line voltage is applied, may be spotted. If there
is a short-circuit between one side of the line and the chassis, there will be a
fifty-fifty chance of burning out another antenna coil as soon as the antenna is
connected and the set plugged in. If the side of the line cord that is shorted happens
to be plugged into the grounded side of the light line, nothing may happen until
the plug is removed and turned over; but then the smoke will roll or the fuse will
"The best insurance against lightning damage would seem to be to yank the line
cord whenever a storm is approaching."
"Truer words were never spoken. Putting all your trust in a lightning arrester
is like barring the attic window against burglars and leaving all the rest of the
doors and windows wide open. If all our customers followed our advice and pulled
out their TV line cords when a thunderstorm approached or when they left home for
any length of time in the summer, our lightning repair business would drop to a
very low figure."
"Then why tell 'em?" Barney demanded.
Before Mac could answer an elderly lady entered the shop. Miss Perkins was on
vacation; so Mac went into the front part of the shop to give the customer her small
"Here you are, Mrs. Nelson," he said.
"I found the noise you mentioned, and a new tube took care of that; but I'm puzzled
by your saying the radio was dead. It started off as soon as I turned it on, and
I have kept it running for two whole days without any cutting out. Could it have
been possible you did not have the clock switch turned on? This is one of the few
sets I have come across that uses two turn-on switches connected in series: one
on the volume control and one on the clock."
"You mean those little knobs on the clock have something to do with the radio?"
the little old woman asked with a puzzled expression.
It quickly developed the radio was a Christmas present and that the donor had
not explained how it worked. The owner had never known there was any connection
between the clock and the radio. To her, a clock-radio was simply a clock and a
radio. Fortunately, the clock switch had been left in the "Manual" position; so
the switch on the volume control had served to turn the radio on and off. An inquisitive
visiting grandson had apparently turned the clock switch to "Off," where Mac had
found it; and so the volume control switch could not turn on the set.
Gently and patiently Mac explained the working of the combination. Not only did
he show her how to set the clock controls so that the radio would be turned on or
off at a given time, but he also made certain that she understood the clock switch
had to be left at "Manual" if she wished to use the volume control switch for turning
the set on and off.
"Boy! How dumb can you get?" Barney sniggered after she had thanked Mac warmly
and departed with her set.
"Let's have none of that kind of talk!" Mac said sternly.
"There's no reason why she should understand the workings of a clock-radio without
instruction. And there are dozens of fields, from churning butter to diapering babies,
in which her knowledge and experience would make us both look like real dopes. Let
me make it clear for once and for always that in this shop our Senior Customers
are to receive every courtesy, consideration, and kindness."
"I'm sorry, Mac," Barney said with a red face. "I know better than to say anything
"Sure you do. I heard you griping the other day how color TV, printed circuits,
u.h.f., and transistors were piling in on us faster than we could grasp them; but
did you ever stop to think what a bewildering array of basic new inventions and
discoveries have come into use during the span of that woman's life? Electric lights
and power, automobiles, airplanes, radio, TV, motion pictures, jet propulsion, antibiotics,
atomic energy - these are just a few of the things she has had to understand and
learn to live with and use during her lifetime. It is truly wonderful that she and
her contemporaries have been able to take all this in stride."
"That's a fact," Barney warmly agreed.
"And while we're on the subject, I want you to give these older customers of
ours a little special treatment. I'm not saying this just out of sentiment. As the
normal life span increases, elderly people are becoming more and more important
to our economy as a whole; and they play a particularly important part in the radio
and TV service picture."
"To active working people, radio and TV are just a couple more forms of amusement
bidding for attention; but to many retired persons they constitute practically the
only form of entertainment regularly enjoyed. This makes the radio receiver or TV
set assume an importance not always understood by the service technician. It's hard
for him to comprehend how lonely an elderly person may feel when his or her set
is out of order; yet both of us have heard these people say it's almost like having
someone dead in the house when the radio or TV is on the fritz."
"Then you want me to make every effort to return old people's sets in a hurry."
"That's the ticket. I hope that we can do a little plain and fancy record breaking
in this part of our servicing operation.
"More than that. When you return a set to them, make sure they know how to get
the most out of it. Try to have the owner tune the set while you watch. If he's
doing anything wrong, tactfully show him how it should be done. You'll find these
people are deeply grateful for any help you can give and for your intelligent interest
in their problems. They make loyal, highly-vocal customers who will provide us with
an astonishing amount of effective word-of-mouth advertising once they are convinced
we are honest, capable, and friendly. Be sure and note that word 'friendly.' It
is important in dealing with any customer, but friendliness is especially appreciated
by elderly people."
"Gotcha!" Barney exclaimed as he made an understanding circle with his thumb
Mac's Radio Service Shop Episodes on RF Cafe
This series of instructive 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 Radio & Television News
magazine (which itself started as simply Radio News), and then changed
its name to Mac's Service Shop after the magazine became
World. 'Mac' is electronics repair shop owner Mac McGregor, and Barney
is his eager, if not somewhat naive, technician assistant. 'Lessons' are taught
in story format with dialogs between Mac and Barney.
Posted June 17, 2019