National Panasonic T-100D inside Look

The T-100D has an interesting build because it is from a time when many manufacturers were switching over from valve technology to transistor technology. Consequently, these early radios had a metal chassis and large slug-tuned coils that valve circuits usually employed, and this is what makes them very desirable with radio enthusiasts.

This is a very neat and simple design where they have kept the coils on the metal chassis. There is a small printed circuit board (PCB), which has the intermediate frequency (IF), and audio frequency (AF) stages, as well as the oscillator and mixer. The PCB construction appears to include a solder flow, however the overall construction would have been by hand. To the inexperienced it can look messy, however this is a hand built radio, and no two radios would have been identical.

Soldering all the wires and installing the light switch and meter would have required skilled labour. They would have had a person to install the string for the tuning dial and band indicator mechanisms. There would also have been a person to tune all the coils, which by no means is a simple matter. Whilst it would take me half a day using an oscilloscope, the woman at the factory would have been able to tune all of them in seconds.

The manufacturer has also included information by way of a label to show how the tuning string installs, so if it breaks, then someone in the UK will have the intelligence to install a new one. Providing information in this way is extremely useful to an engineer, and I wish they had included a circuit diagram, which was a common practice back then. Many people will remember radiograms and televisions having labels showing valve positions, and audio connections. If you had a Philips EL3302 then it would have had a little circuit diagram attached to the inside back cover. Back then, manufacturers expected their products to last almost forever, and they provided information so that someone could repair it.

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