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
By John T. Frye
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
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,"
"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 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.