Evolution of Electronic Construction

Before the widespread use of printed circuit boards (pcb) there were some attempts to improve the construction of electronic devices. One reason was to get greater uniformity and accuracy mainly on high frequencies. Of course a welcome effect was speed up manufacture for lower cost and ease of repair.

The Ratsnest

Conventional wiring and placing of the components was established between tube socket pins and some solder posts. The result was a dense 'rats-nest' which today will make restoration a challenge. It was widley used for consumer products until the late sixties (photo taken from museum's hallicrafters SX-122 shortwave receiver):

A first step - the CTC post

Two rows of small bakelite strips with metal solder pins (CTC posts) made component placing more uniform. As nearly all components were of axial type it was the logical choice. All connections were still conventional wired. This standard two row layout was eased by the introduction of double rowed bakelite boards:

First Printed Wires

Based on the double rowed bakelite boards some early printed circuit boards were used by Hewlett-Packard. On the now phenolic boards few copper trains on one side replaces some wires (here opposite side with white silk screen):

Ceramic donates neat Layouts

Tektronix take up the CTC posts and developed a ceramic variant which set a new standard for electronic products. As more and more transistors appeared in their instruments the former advantage was lost and finally Tektronix shifted to pcb's.

A three-dimensional circuit - the Craigmount

All construction used one plane which was typically no problem, as the cabinets were quite large. Hewlett-Packard and Beckman/Berkeley were producing electronic counters in large numbers. Both were faced with the problem of small subassemblies for their decade counters. While hp used pcb layout, Beckman/Berkeley invented the so called Craigmount assembly. The components were put in a bakelite plate with predrilled holes and were soldered with their leads on both sides. This enabled very compact subassemblies and needed less wiring (photo shows B/B 705AH decade counter assy):

Wire-Wrap Technology

Bell Labs developed the Wire-Wrap to speed up wiring of telephone equipment and makeing service easier than with solder junctions. Early computers did use this technique too, to get the shortest connection between two points.(photo shows backside of microprocessor system made by S. Graef)

Rocketproof Wiring

The Welded-Cordwood Construction was born at the military. Few compunents are welded (not soldererd) togehtert to a three-dimensional box. The box is then potted with a plastic material. On one side there are remaining wires, which form the pins for soldering the boxes to a printed-circuit board. This sort of circuit is extremelx reliable and shockproof because of only few solder points. Use was military equipment like aircraft and missile electronics. (photo shows plug-in of military module taken from Lockheed F-104G anti-stall-controller).

Printed Circuit Board

All you us are familiar with the green board and the black bugs on it (photo shows main pcb of computer Commodore CBM8032).