This episode of
"Mac's Radio Service Shop" is a prime example of the difference between a
business owner and an employee when it comes to always thinking about how to
make things more efficient and attractive to customers - and therefore more
profitable. To be fair, there is no reason to expect an employee to have as high
a level of devotion as an owner other than for better job security. The October
1950 story entitled "Mending Harness," appearing in Radio & Television News
magazine, is a prime example. Mac, the proprietor, had spend many hours in the
evenings completing service jobs and clearing the shop of its sizeable backlog.
Barney, the employee, loved the situation since he thought it would mean some
slack time for him. Mac, though, planned to use that time for repairing,
aligning, and improving the test equipment - something that had gone wanting
during the busy times. As always, Mac's Service Shop docu-dramas are a good mix
of useful lessons and good humor.
Mac's Radio Service Shop: Mending Harness
By John T. Frye
"There!" Mac said as he placed a little white radio on the "repaired" shelf;
"that's the very last set we had to fix. We are all caught up."
"Hey!" his assistant, Barney, said in wide-eyed amazement, "what goes here? That's
the first time I ever remember that happening. Is business falling off? Have you
got my Social Security paid up?"
"Now don't get excited," Mac said soothingly. "Business is all okay. I have simply
been putting in a lot of overtime lately. My wife has been visiting her sister in
St. Louis this past week, and I got the fidgets sitting around home by myself; so
I have been coming down here every night and knocking out several sets. You better
turn in your Boy Scout badge for not having been observant enough to notice this."
"Well," Barney said complacently as he tilted the stool upon which he was sitting
back against the wall and propped his generous-sized feet up on the service bench,
"it is a revolting development, but we may as well face it. Just wake me up if any
business comes in that requires my personal attention."
"Oh no you don't!" Mac said as he scooped a handful of shredded paper out of
a tube-shipping box and sprinkled it over Barney's recumbent form. "We are going
to do what we used to do when I was a boy down on the farm and a rainy day kept
us out of the fields; namely and to wit: mend harness."
"Mend harness ?" Barney questioned.
"I always knew you worked me like a horse, but I never caught sight of any harness
"A figure of speech, my boy," Mac explained. "I mean that we are going to take
advantage of this lull to overhaul some of our equipment and otherwise catch up
on some of the little things around the shop that we do not have time to take care
of when business is rushing."
"That's got a kind of nasty sound to it," Barney commented dubiously. "What are
some of those 'little things'?"
"First, I want every instrument in the shop thoroughly cleaned and waxed. I especially
want those instruments that we take with us to the customer's home to be gleaming.
A dirty instrument with frayed cord and test leads makes an impression on a customer
about like that he would have if his doctor used a rusty stethoscope or a soiled
tongue-depressor on him; but you will note that a doctor, that wisest of 'servicemen,'
always sees to it that his instruments are immaculate.
"Replace any a.c. cords that show the least sign of insulation failure, and make
up new test leads for all of the portable instruments. While you are at it, too,
you may as well make up a few new test lead terminations."
"What's a 'termination'?" Barney demanded.
"A big word to describe a useful little gadget. In ninety per-cent of the cases,
the ordinary test prod is all you need; but there are times when it is handy or
even necessary to have a needle-point prod or one with a clip on the end of the
lead. It is foolish to lug around a pair of separate leads for each of these rarely-needed
cases. If an alligator clip or a phono-needle chuck is soldered to a phone-tip jack,
this jack can be slipped over the end of the test prod and so will convert it to
whatever type of lead you need. These 'terminations' take up lots less space than
do complete and separate test leads and serve the purpose just as well."
"Is that all we have to do?"
"Oh no; we are just getting started. I also want you to put a separate line-switch
and pilot lamp on our tube checker. That present arrangement of having the line-switch
on the 'Line Volts Adjust' control is not so hot. I have already had to replace
two of those controls that had the wire elements worn out by the wear produced in
turning the thing off and on. Putting in a separate switch will get away from this;
and, while you are at it, you may as well put in a red-jeweled pilot lamp so we
won't leave the tester on when we are not using it. There is plenty of room."
"And may I be so bold as to ask what you are going to be doing while I am slaving
away on these projects?"
"You may," Mac said with a grin. "I am going to check and recalibrate our test
oscillators. After those hot humid summer days, they are bound to be off a trifle;
but if I correct them now, at the beginning of October, they should be all right
all during the winter. I want to make sure that when our test oscillator pointer
says '456 kc.' it is 456 kc."
"Is that so important? I don't think you would see much difference in tracking
if the i.f. were off four or five kc.'
"The difference in tracking is not the whole story. It is important that the
i.f.'s be right on the nose. Broadcast stations are placed on the even ten kilocycle
frequencies. The i.f. frequencies are seldom divisible by ten. This is no accident.
If, by error, we should set up the i.f.'s on 450 kc., two strong broadcast stations
450 kc. apart could mix right in the input circuit and both ride on through the
i.f. channel; but if our i.f. was properly set on 456 kc., this could not happen,
for no two broadcast stations are ever 456 kc. apart. What is more, setting the
i.f.'s off their correct frequency by only a couple of kilocycles will often put
a disagreeable 'birdie' on a particular station."
"How are you going to do this re-calibrating ?"
"If the frequency is not too far off, I intend simply to make a correction note
and paste it on the generator. For example, it may say, 'Set pointer to 454 to get
456 kc.' I prefer doing this to disturbing the insides of the instrument, and I
know by experience that the oscillator may drift enough by spring so that the dial
reading will again be correct. Of course, if any major discrepancy is found, I'll
re-calibrate the whole thing in accordance with the information given in the instruction
"Where are you going to get your frequency standards?"
"Silly boy!" Mac chided. "I'll use the broadcast stations and WWV, of course.
For the low frequencies, harmonics that fall in the broadcast band can be used.
For example, I can locate 455 kc. very exactly by making the second harmonic of
this frequency zero beat with the carrier of the broadcast station on 910 kc. For
higher frequencies than the broadcast band, I can use fundamentals or harmonics
that fall on the various WWV frequencies of 5000, 10,000, and 15,000 kc. The crystal
markers we have for the i.f. frequencies of our TV generator make it unnecessary
for us to worry about the calibration there.
"I also intend to check all of our meters. This afternoon I am taking the multimeter
to the high school physics laboratory to set the low-range d.c. scales exactly on
the nose as compared with a standard cell they have there. The a.c. ranges will
also be checked against the fine a.c. meter in the lab. Then I'll bring the multimeter
back to the shop and check all of our meters against it. The multimeter and another
meter can be connected in parallel across a flashlight battery, a "B" battery, etc.,
and the two readings compared. Of course, I need not tell a seasoned old technician
like yourself that both meters should be connected at the same time rather than
separate readings being taken to make sure that the voltage does not change with
the difference in loading between the multimeter and the other meter."
"How about the ohmmeters?"
"I'll check those by testing several wirewound resistors. Those wirewound jobs
are plenty accurate enough for that purpose."
"Just supposing," Barney said cautiously, "I was able to get all of the instruments
cleaned up and the tube-tester fixed before supper time. Would you have any other
'little thing' you would want me to do?"
"Oh, yes; I've got a job you will love because it is a sitting-down job. As you
know, we take about every radio and television trade magazine on the market, and
there is a wealth of fine, current material in these magazines that can be found
nowhere else. The only trouble comes in being able to put your finger on a particular
article when you want it.
"Fortunately, some of the editors appreciate this problem and do what they can
to help. For example, Radio & Television News prints a complete annual index
in their December issue.
"What I want you to do is to go back through our entire file of magazines and
clip out all of those indices - indexes to you - and arrange them in a loose-leaf
notebook. Then when we want some information on a particular subject - say wire
recorders, for example - we can look in this magazine index book and quickly sort
out the issues that carried information on the subject. After that - Say, Junior,
what are you looking so down-in-the-mouth about?" Mac broke off to ask.
"Well," Barney said as he got a bottle of carbon tetrachloride and a can of paste
wax out of the cupboard, "I was just thinking that it will take me a full week of
ordinary working days to recover from the effects of this one day that we had nothing
Posted April 12, 2022
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 April 1948 in Radio News
magazine (which later became Radio & Television News, then
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.