Retrotechtacular: Tinkertoy and Cordwood in the Pre-IC Era


It is widely accepted that Gutenberg’s printing press revolutionized thought in Europe and transformed the Western world. Prior to the printing press, books were rare and expensive and not generally accessible. Printing made all types of written material inexpensive and plentiful. You may not think about it, but printing–or, at least, printing-like processes–revolutionized electronics just as much.

In particular, the way electronics are built and the components we use have changed a lot since the early 1900s when the vacuum tube made amplification possible. Of course, the components themselves are different. Outside of some specialty and enthusiast items, we don’t use many tubes anymore. But even more dramatic has been how we build and package devices. Just like books, the key to lowering cost and raising availability is mass production. But mass producing electronic devices wasn’t always as easy as it is today.

Pre PCB

At one time, electronics were assembled by hand with point-to-point wiring and a variety of terminal strips and connections (for example, see the 1948 Motorola TV set to the right). Wires formed connections to the terminal strip (the component with five lugs near the top left), sockets, lugs on controls, and components.

This is in stark contrast to today where all the components would mount on a printed circuit board (PCB). Actually, PCBs in some form have been around since the early part of the 20th century. Even [Thomas Edison] tried to plate conductors on paper.

Despite some limited use, PCBs didn’t really take off until World War II. German mines and U. S. proximity fuses used them. Still, it would be well into the 1950s, though, before consumer electronics started to really use PCBs.

There are some technical advantages (and disadvantages) to using PCBs. But the most obvious advantage is just in labor savings. Assemblers used to use photographs and checklists to be sure they made every required connection. Not only was this labor-intensive, but it was also prone to error. The photo below shows an RCA radio factory in 1937.

Despite the name, printed circuit boards are not always printed (in fact, today, they are rarely printed). But the idea that you can make one template and automatically make tens, hundreds, or thousands of identical copies is the same idea of the printing press.

Pre IC

The other printing-like process that changed electronics forever was the integrated circuit. While the PCB allowed wires to be reproduced flawlessly, the IC lets you create entire circuits with many components and then reproduce them relatively easily. There are other advantages, too (miniaturization, close matching of active devices, etc.). But the ability to produce a CPU, for example, with all its components and wiring repeatedly using a reasonably simple process has driven price and innovation in the electronics business since it became available.

If you think about it, the IC makes a lot of things practical. Let’s say you are going to create a fish finder that uses a sonic pulse to find your dinner (or the bottom of the lake). You probably need an instrumentation amplifier. How much could you spend to develop it? You probably can’t sell millions of fish finders, so you won’t have a lot of time to refine your design. It probably can’t have too many components in it either, or the price will go up and you’ll have even fewer sales.

You can buy an instrumentation amplifier as an IC very inexpensively. The company that makes it probably spent years getting it to the current state that it is in, going through multiple product iterations. Although more components do drive up the cost of an IC (due to driving up the die size), it doesn’t raise it very much, especially at smaller die sizes where manufacturing processes have very high yields. So your choice is to design your own inferior amp using a few devices at great cost or spend the buck or less to get a well-tested design with dozens of devices and great specifications. Easy choice. Of course, if you can find a highly-integrated fish finder IC (don’t laugh, the LM1812 was a thing; see page 81 of this old Popular Electronics) then you can use that and be done with your whole design in an afternoon.

Better Living Through Military

The military is often the first to find ways to pay for new technology. They had been searching for a reasonable way to get more reproducible electronic assembly for some time. The U.S. Navy, for example, had project Tinkertoy. The idea was to make little modules out of ceramic with silver patterns painted on them. Components like resistors and capacitors could also be placed on the boards using automated processes. At the end, modules stacked together and little tabs around the edges served as a guide for interconnection wires as well as keys for orienting the boards.

You can see a very detailed–and a little stiff–video from 1953, below, explaining how the system worked. NIST (the technical muscle behind Tinkertoy) also has a photo gallery of both the devices and the pilot plant.