Early last spring, we featured a book review, as part of our occasional Books You Should Read series. Usually these are seminal tomes, those really useful books that stay with you for life and become well-thumbed, but in this case it was a children’s book. Making a Transistor Radio, by [George Dobbs, G3RJV], was a part of the long-running series of Ladybird books that educated, entertained, and enthralled mid-20th-century British kids, and its subject was the construction of a 3-transistor regenerative AM receiver. If you talk to a British electronic engineer of A Certain Age there is a good chance that this was the volume that first introduced them to their art, and they may even still have their prized radio somewhere.
Making a Transistor Radio was a success story, but what’s not so well-known is that there was a companion volume published a few years later in 1979. Simple Electronics was part of the imprint’s Learnabout series, and it took the basic premise of its predecessor away from the realm of radio into other transistor circuits. Transistor timers and multivibrators were covered, Morse code, and finally quite an ambitious project, an electronic organ.
Opening the book it is evident that there has been a slight cultural shift since the first volume was published. The typography is much more modern in feel, and the picture of the child experimenter on the inside of the cover is a photograph of a late-70s young girl in place of the 1950s-style boy wearing a tie building the radio. The practical nature of the writing hasn’t changed though, while it states that some of the background information is not being repeated from Making a Transistor Radio we are taken straight into the deep end with a section on the tools required to work with the series’ signature screw cup on wooden baseboard construction technique.
The original book used germanium transistors from the Mullard OC series, OC71s and an OC44. These were some of the earliest British transistors, and as I can attest from building my radio in that period, difficult to obtain by the late 1970s. This book has therefore moved on to a later design, the AC128. Still a germanium PNP device, but this time in a metal can and crucially still available at the time due to having been a part used in more than one mid-70s colour TV set. We’re given a no-nonsense introduction to the device, told about its package, pinout, and schematic diagram. It’s refreshing to see a children’s book in which the child is introduced to such an adult subject as this without being constantly reminded that they are a child.
We then spend a couple of pages looking at a transistor as a switch. A 10K base resistor is used to bias an AC128 with a flashlight bulb as its collector load, and with a flying lead to the negative supply (remember this …read more
Source:: Hackaday