November 1973 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Even if you are not, never were, and don't plan to be a color television serviceman, this installment of Mac's Service Shop that appeared in a 1973 issue of Popular Electronics provides an interesting insight into the manner in which the electronics industry was rapidly changing in the 1970s. By 1973 most manufacturers had fully committed to all solid state circuitry (except for the CRT, of course), and the competition was focusing on customer satisfaction. Point-to-point wiring of chassis with leaded resistors, capacitors, inductors, and interconnecting wires and coaxial cable gave way to multiple printed circuit boards (PCBs) with a maze of interconnecting wire harnesses. In theory the scheme was much more reliable and serviceable, and for the most part it was. The problem was that a lot of service guys were still struggling to come up to speed on the newfangled technology. Trying to use a 500 watt soldering iron with enough heat and thermal mass to solder copper downspout seams wreaked serious havoc on a PCB. The lower wattage components used with lower voltage and power circuits could easily be destroyed by excess heat. In order to help mitigate the issue, manufacturers provided swappable subassemblies that would expedite the troubleshooting and repair cycle, resulting in lower bills from the service shops. Bad PCB assemblies were returned to the factory or authorized repair centers, with a credit given to the service shop. Within three decades, yet another new paradigm would surface where most consumer electronics were cheap enough and became obsolete fast enough that a failed unit was simply discarded and shipped on a barge to a desert area in Africa where starving, shoeless kids burn piles of electronic waste (e-waste) and attempt to recover sellable metals from the process while inhaling poisonous fumes.
Mac's Service Shop: Motorola's 1974 Color TV Receivers
By John T. Frye, W9EGV, KHD4167
I see you're at it again," was Barney's early morning greeting to Mac, his employer, who was sitting at a back bench literally covered with pictures, service manuals, press releases, and other manufacturer's literature, all bearing the name of "Motorola" or that company's distinctive emblem: a heavily shaded, stylized black "M" within a circle.
"Yes," Mac replied; "now that we've boned up on Zenith and RCA color sets, I think it's time we studied the 1974 offerings of another leading manufacturer, Motorola. The first thing that impresses me, naturally, is the serviceability of these color sets. As I'll explain later, that's no accident. But first let's back off and take a panoramic view of the whole color line.
The Entire Line. "By my count Motorola offers 37 color TV receivers that include one each of 12", 14", 16", and 17" portables; two 18" portables; five 19" portables; three 21" table models; three 23" consoles; eight 25" Quasar II consoles that are solid-state except for four chassis tubes; eleven 25" Quasar consoles that are all solid-state; and one unique 21" table model that can be switched to receive either the NTSC color system we use in this country or the PAL system used in Europe. All models have 'Insta-Matic' color tuning in which the push of a single button automatically balances color hue, intensity, brightness, and contrast and activates the automatic tuning. All console models except one 23" use black-matrix, negative-guard-band picture tubes, and this type of tube can also be had in two of the 19" portables.
"The 'Satellite Remote Control' is available on one 19", one 21", and eight 25" models. The mechanical ultrasonic transmitter has only two buttons that turn the set on and off, select a desired vhf or uhf channel (except for the 19" portable which selects only vhf channels), and adjust the volume. This simplified control is possible because the Insta-Matic circuitry of the chassis maintains a stable color picture when changing channels. The vhf tuners are of the type that permits pre-set fine tuning, and the solid-state uhf tuner comes in four versions in different models: 70-detent-click, continuous, pushbutton, and varactor tuned. In the pushbutton type, up to five uhf channels can be set up for pushbutton selection just as you set up a car radio."
"The thing that impresses me," Barney interrupted, "is that 'Works in a Drawer' solid-state chassis that pulls out from the front of the set on guides. You can have the whole chassis right there in front of you, with the picture in plain view, while you probe around with a diddle stick or tap components to locate an intermittent connection. A Motorola service technician told me 94% of the components in these sets are mounted on plug-in modules, or 'panels,' as he calls them. Even tuners plug in, and anyone who has had to unwire an easily damaged, easily misaligned tuner and wire in another in cramped quarters to see if that is the trouble knows what a blessing a plug-in tuner can be. He says Motorola sets use up to ten panels and that the most expensive, the Electronic Power Supply Module, costs the customer only $18 on an exchange basis."
Electronic Power Supply Module
Photo shows a comparison of the Motorola "JA" electronic power supply (near right) used in the Quasar sets and the previously used power supply. The new unit weighs about 1 3/4 pounds as compared to 13 pounds for the original iron-core power supply.
"That power supply, introduced in the 1972 models, is one of the most interesting engineering features of these sets," Mac commented. "Essentially it transforms rectified 60-Hz current into 15,750-Hz pulses that are applied to the primary of a lightweight 'flyback' transformer whose secondary then furnishes seven different 15,750-Hz ac voltages that are rectified to produce positive and negative voltages for powering the chassis and heating the filament of the CRT, as well as high-frequency ac for heating pilot lamps.
"Dc through the primary is turned on at a 15,750-Hz rate by a switching transistor switched by a square-wave input. This input originates as pulses from an oscillator locked in sync to the horizontal sweep circuit. These pulses pass through a shaper that transforms them into square waves and thence to a driver stage to the switching transistor. This switching transistor is turned on only when the positive-going portion of the square wave is present at its input. How long it remains on, and consequently how much power is delivered to the primary, depends on the duration of this positive portion of the square wave.
"This affords a means of power and voltage regulation. Suppose you increase the brightness and so the load demand on the secondary. This drops all secondary voltages. A sensing winding on the secondary passes this voltage drop to a voltage-regulating transistor whose resulting changed output is passed to the shaper stage. There it widens the square wave delivered to the driver and thence to the switching transistor. The resulting longer on time of this switch delivers more power to the primary and brings the voltage of the secondary windings back up to where they were before the brightness was advanced. A decrease in power demand in the secondary has the opposite effect: it causes the VR transistor to narrow the square wave put out by the shaper and so reduce power in the primary and voltage in the secondary.
"Still another feature is automatic shutdown of the power supply if the load increases to an unsafe level. An SCR samples the emitter resistor voltage of the switching transistor. If an overload causes this voltage to rise above a pre-set level, the SCR fires and short circuits the square-wave input of the switching transistor, preventing it from turning on. The SCR continues to conduct and keep the switching transistor off until all power is removed by turning the set's on/off switch off momentarily. The SCR then becomes non-conductive and allows the power supply to operate when turned on."
"I'd think that kind of power supply would have lots of advantages."
"It does. First, there is isolation of the chassis from the AC line. It regulates for line voltage changes in the same way it regulates for power demand changes. The powdered-iron core of the high-frequency transformer is much lighter than the heavy soft-iron cores necessary at 60 Hz. At the higher frequency, filter capacitors are substantially smaller in both size and capacitance."
Dual System Sets
"How about that set that operates on both the NTSC and the PAL systems?" "That's the ZX600JW Model obviously intended for people who globe-trot and don't want to have to buy a new TV set every time they cross the pond. It covers all NTSC channels, all PAL uhf channels, and eight PAL vhf channels. PAL channels 2, 11, and 12 are out of the receiver tuning range. The chassis includes both 4.5-MHz (NTSC) and 5.5-MHz (PAL) sound i-f and color processing circuits for both systems of transmission. Switching diodes, controlled by a PAL-NTSC switch on the front panel, activate the appropriate circuit. Tuners, part of the video i-f, the audio output, and the deflection circuits are common to both systems. To change from one system to the other, you simply push the PAL-NTSC switch and fine tune the desired channel. This initial fine tuning is necessary because of the difference in channel allocations in the two systems. For example, in the PAL system the video carrier, chroma carrier, and sound carrier frequencies of channel 3 are respectively 55.25 MHz, 59.68 MHz, and 60.75 MHZ. In the NTSC system, they are, for channel 2, 55.25 MHz, 58.83 MHz, and 59.75 MHz. Here is the service manual on this cosmopolitan TV receiver. I think you'll find it technically very interesting, even if you never expect to service one."
"Okay, but you said you'd tell me why the serviceability of Motorola color sets is no accident." "That's right. I'm always interested in the basic philosophy of the manufacturer of any product, and we have a rare opportunity to examine the Motorola philosophy through a speech delivered by Edward P. Heavey, Jr., Vice President & General Manager of the Consumer Products Division of Motorola, Inc., to the American Management Association in September, 1971. Let me read you a few excerpts from it:
"'Change is taking place throughout the land. ... There are early warnings that an anti-materialistic mood could be building. More Americans appear to be interested in meeting their basic needs as easily and inexpensively as possible. ... Many are moving away from the big shiny cars to small cars. ... There's less interest in big TV-stereo combinations and more demand for smaller sets. People want reliability and serviceability from their cars and TV sets.
... The product [they buy] often costs less than the service performed on that product .... People are angry. Mad. Sore.
... This is what consumerism is all about, gentlemen - service.
"'For too long, service has been treated as a dingy back-room operation in too many companies. Top management has paid little or no attention to this part of the business. ... We have been so busy building new and better products. ... that we simply have not learned how to serve the customer ... Top management had better find out where the service department is located, who runs it, and how well he runs it. ... The head of service should be a part of top management. In my company, he is. My service manager is a vice president. Service requires that kind of authority and visibility today. We "think" service from the design of the color TV until the ultimate consumer tells us he is happy with our product. ... I am completely convinced that success and even survival of a company in the 1970's and 1980's will depend upon how well that company serves the consumer:
"There was lots more to the speech," Mac said, laying the paper aside, "in which he tells what Motorola has been doing about improving service to their customers. This does not stop with improving the serviceability of their sets with the module concept - which they pioneered in 1967 - and with the 'Works in a Drawer' idea. He is opposed to what he calls 'cosmetic consumerism' in which a token attempt is made to placate the consumer with 'plastic programs announced with great fanfare: Such programs include the listing of a trouble phone, an expensive media campaign, and the appointment of a vice president of consumer affairs. As Mr. Reavey points out, 'When an angry customer contacts you, it's just possible you've already lost him as a future buyer, no matter how rapidly and efficiently you respond to his call for help.'
"So, according to Mr. Reavey, Motorola has been trying to anticipate complaints. They tested a program of phoning purchasers of Quasar TV sets to see if the owner was satisfied with his purchase. If not, they went out and saw to it that he was. Mr. Reavey himself began dropping into consumers' homes as he went about his business. He took along a service manager, and if the Motorola customer had a problem, the service manager fixed it. Public reaction to these programs was about the same as would be evoked by the advent of the millenium!"
"I can well imagine," Barney exclaimed. "But that sounds as though someone might have been listening to us after all. I've heard you say a hundred times that it is downright stupid not to have a good technician play a major role in the design of a color receiver; and how many times have I seen you pick up the telephone and make sure that a set we'd fixed was working satisfactorily?"
"All that proves," Mac said with a grin, "is that a really good idea is seldom the property of one person!
Posted October 24, 2019
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.