[Table of Contents]People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April
1985. As time permits, I will be glad to scan articles for you. All copyrights (if any) are hereby acknowledged.
Point-to-point wiring of
electronics assemblies is rarely seen these days. For that matter, the use of leaded components is rarely seen
these days. The advent of printed circuit boards was a real breakthrough concept when they became commercially
viable in the 1950s. As the comic at the bottom of the page suggests, many people did not even know what a printed
circuit board was.
The air traffic control radar unit that I worked on in the USAF had all point-to-point
wiring in a trailer-full of chassis. Terminal strips and bus strips, bifurcated terminals, tube socket terminals,
and studs from relays and switches were the connection points that the leaded components and wiring stretched
between. Compared to a PCB (especially multi-layered through-hole), servicing those assemblies was a piece of
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Printed Circuits Come of Age
By ALLEN LYTEL
circuits have come of age. Today they are an integral part of almost all electronic equipment. Look at the nearest
device: if it has been made in the past year, the chances are that in it you will find printed circuits or
Some of the newest uses for printed circuits are in the instrument cluster connections in an
auto dashboard (see photo above). Guided missiles have compact, reliable controls which use printed circuits, and
so do midget tape recorders, jet planes, hearing aids, electronic organs, and hundreds of other devices.
The most common type is an insulating board* with a pattern of conducting wires (below right). A photo or printing
process transfers the design to the copper-clad base and an etching process removes the excess copper, leaving the
circuit. In other methods, the conductors are built up on the insulated base. Next step is the placement of
components, handled mechanically. In one machine all heads are controlled simultaneously, and as the board is
positioned, all the capacitors and resistors are inserted in one operation. In another machine, they are inserted
one at a time as the board moves down the line. After the components are inserted, all parts are dipsoldered in
place in a single operation.
Printed Circuit Board (PCB)
Figures 3, 4, and 5
The use of printed circuits has led to the development of modules. These are complete circuits such as audio
amplifiers, cathode followers or pulse generators.
Modules are built on a single board as a unit, acting
as a standard circuit which can be used in different end products. Figure 1 on the next page shows an experimental
TV receiver built of 17 modules which hold 153 of the 195 components (resistors, capacitors, etc.) exclusive of
the tuner. Other modular construction is of the type in Fig. 2. These are plug-in boards as used in many computers
and industrial controls. Tube and tubeless types with diodes are shown.
These modules can be made up of
smaller units. For example, several resistors and capacitors can make up a package -- a "super component" -- and
can be used on a printed-circuit board (Fig. 3). In another way of treating the same situation, the components are
encapsulated in phenolic material (Fig. 4).
The newest development is flat Tape Cable (Fig. 5) which
eases the task of interconnecting printed wiring (see October issue of POPULAR ELECTRONICS, p. 72).