Transistors and semiconductor diodes have been manufactured in Japan since the 1950s. However it is difficult to find information about the early history of this industry and so this page is rather less informative than most of my other 'country' pages. In particular I do not know if Japan made any semiconductor diodes prior to the invention of the transistor, for example, germanium radar diodes. I also suspect that the Japanese transistor industry got off to a relatively late start because of the state of the country after the second World War. I could be wrong about that though.

Once they did get started, there were a good number of Japanese companies involved, many of which are now worldwide household names for electrical goods. These include:

Somewhat similar to the USA, the Japanese manufacturers all agreed quite rapidly to use a small number of standard series of part numbers and device encapsulations, specified by the Electronic Industries Association of Japan. However, there was a short initial period when nicely idiosyncratic numbering and forms were used, and I mainly show those below.

There used to be one site on the Web that was outstanding in its display of early Japanese semiconductors: that of Masahiro Nakahori. It contained little descriptive text, but a wealth of images. Sadly it seems to have disappeared.

I do not possess all the transistors below, in fact I am seeking many of them and also data on them. It is noted in the text where that is the case. If you can help, please

T1698 data

Inside the box of my Sony 1T21 diode (see below) is a small datasheet in Japanese that lists a number of transistors, one of which is the T1698. The Western Electric type 1698 is a point-contact transistor. On the Web, there is a Kobe University research paper on the approach to start-up companies in Japan and the USA, taking the early transistor industry as an example. It confirms my long-held suspicion that the Sony T1698 is a point-contact transistor, probably the only such type ever made in Japan. It was used in the ETL mark III, which the paper states was "the world's first stored-program transistor computer". If anyone can translate the shown extract from the data sheet, or provide information about this transistor, or examples of it, please

1T21 transistor

This image shows what is possibly my oldest Japanese device: a 1T21 germanium diode made by Tokyo Tsushin Kogyo, also known as Sony. This was presented to me in 1996 by a Japanese correspondent called, I think, Minoru Moru who informed me that it was once owned by the president of Sony. Regrettably I have lost the details of this exchange. If you have any information or data about this diode, please

1F21 diodes

Here is a set of five 1F21 diodes made by Fujitsu, in a long matchbook-style carton printed 'FUJIODE Germanium Diode'. I speculate that they have similar characteristics to the 1T21, but have no data at all. If you have any information or data about this diode, please

2T65 transistor

I am unsure as to what might be my oldest Japanese transistor, as I have no data on the earliest types. Sony are known to be the first Japanese company to have taken out the Bell Labs license for manufacturing transistors. The little data sheet in the 1T21 diode box lists the following devices in addition to the T1698:

Regrettably, I have none of these apart from the 1T21. My image shows a 2T65 which is not in this list but is not far away in terms of numbering. If you have any information or data about these transistors, or have any for sale or exchange, please

Hitachi transistors

This image shows a pair of early Hitachi types: HJ17D and HJ34A. If you have any information or data about these transistors, please

MA23 usage MA23 transistor

Another early device is this MA23(B) branded National, which uses a Philips Group glass SO-2 capsule. National is a brand used by Matsushita, also known as Panasonic. Thanks to a correspondent, Takashi Yamasaki, I now know that this is in fact a varistor. However it is not a standard one: early semiconductor makers in Japan sold defective transistors as varistors or zener diodes. The MA23 was called "Variode" by Matsushita Electric and Japanese radio makers used MA23's base+collector and emitter as the varistor's cathode and anode respectively. Three versions were suffixed (A), (B) and (C) depending upon their forward voltage at 1mA.

OC45C transistor

Here's another brightly-coloured National transistor in a Philips group glass SO-2 capsule. This one even adopts the Philips/Mullard part number OC45, with a suffix C. If you have any information or data about this transistor, please

2SA12 transistor

As I explained above, all Japanese manufacturers rapidly adopted device numbering according to standards specified by the EIAJ, plus standardised packaging from JEDEC. According to that Wikipedia EIAJ article, the different series are:

However, other (probably less reliable) articles on the Web give variations on this. Some of these series are quite obscure, but 2SA to 2SD were very numerous and can still easily be found on eBay. The majority are low to medium power types in the TO-1 metal can like the Hitachi 2SA12 shown. It is quite common for the leading '2S' to be omitted, so that A234, for example, means a 2SA234.

2S56 transistor

A number of transistors in a series 2S were made before the EIAJ numbering had been finalised such as this 2S56 made by Toshiba. If you have original data about this series please

2SB205 transistor

I bought this 2SB205 on eBay simply because of its size. It is a germanium PNP power transistor, but it measures 5cm in length and is quite heavy. I show it next to a standard TO-3 type. Shindengen made a number of types in this package. As far as I know, the only larger transistors ever made were the Russian P207 and P208.

Van der Heem 2SA12 transistor

A company called Van der Heem in the Netherlands used to buy Japanese transistors and rebrand them. The web site of Hans Hilberink shows a 2SA12 transistor rebranded 'vdHEEM' and states that this was done across the "famous 2SA12 to 2SB77 series", mainly manufactured by Hitachi. Radiomuseum shows a similar example of a 2SA235. I purchased a rather dilapidated Erres portable radio that contains a number of such rebranded types: my image shows a 2SA12.