There is one rather puzzling area of UK early semiconductor manufacture. The company Thorn-AEI Radio Valves and Tubes Ltd, which was apparently formerly Edison Swan Electric Co Ltd, manufactured germanium diodes and transistors branded principally 'MAZDA'. They had no connection with the French Mazda brand, rather, they were part of the complex web of companies deriving from the 19th century Edison and Swan Electric Light Company. They are also found branded 'THORN' and, rarely, their devices are branded 'BRIMAR', a name that they bought from STC. Note that, confusingly, devices branded AEI were not made by Thorn-AEI.

Thorn-AEI manufactured semiconductors in early 1960s, but did not move from germanium to silicon except for diodes. If anyone can provide the reason for this, or details of the company history, I would be very interested. They did not use any company logos on their devices: they just bear the word THORN or MAZDA or BRIMAR in capital letters plus the part number. They did not include a date code or other details.

MAZDA semiconductors data booklet

I have only one original data source for these devices, the "MAZDA Semiconductors DATA BOOKLET 1966" shown. The reverse cover is printed THORN . RADIO VALVES & TUBES LTD . 7 SOHO SQUARE LONDON W1 . GERrard 5233

This small booklet contains data sheets for the following devices:


AA120 diode

Thorn-AEI apparently only made one germanium diode, the AA120 shown. Unlike all their other devices it uses a red plastic TO-1 can, which may have a brown plastic sleeve.


AC113 transistor

Thorn-AEI may be branded either THORN or MAZDA, or rarely BRIMAR. My image shows all three brands. All Thorn AEI devices follow the pro-Electron naming convention.

Thorn-AEI transistors

Thorn-AEI low-power transistors nearly all had a plastic sleeve, although a few were unsleeved for use in a heatsink. The colour of the sleeve is specific to the part number, and is listed in the Data Booklet. This resulted in what is clearly the most colourful set of semiconductors produced by any manufacturer.

Sets of thes transistors were sold together as "transistor line-ups" for transformerless audio amplifiers. For example, the Mazda 'Circuit Number' SA11/3 comprised:

The 1966 Data Booklet lists five of these 'line-ups' spanning 1.5 Watts to 8 Watts. I don't know how successful these were but I think it was a clever marketing strategy.


wanted ASY transistors

Thorn-AEI made two germanium power transistors in the TO-3 'diamond' package: the AD140 and AD149. I am seeking the AD140.

MAZDA AD149 transistor

Here is the AD149, with its valve-type box. This type is common as a Philips/Mullard product; it is rare to see it branded MAZDA.


ASY89 transistor

I know that Thorn-AEI manufactured at least one other range of germanium transistors: ASY82 to ASY89. These must be later than 1966. I only have the Brimar ASY89 shown.

I am seeking any ASY type except ASY89 (branded Mazda or Thorn or Brimar). Also original data for this series.

If you know where I can find any of these, please


BA116 diode

Thorn-AEI silicon devices described in the booklet start with this dual-diode type BA116, in a transistor-type case with three pins. It was intended for use in television AGC circuits.

BA126 diode

Next in the booklet is the silicon dual-diode type BA126, in an unusual isoceles-trapezoidal plastic case with four pins.

BY105 diode

The BY105 silicon diode uses the standard VASCA SO-16 can.

BY124 diode

The BY124 silicon diode uses a bespoke plastic encapsulation.

BY130 diode

The BY130 silicon diode uses a cylindrical plastic encapsulation.

Y1909 diode

This Y1909 diode uses a plastic case similar to the BY130. However, such a series is not mentioned in the data booklet. If you know about this device, or anything about the Y series, please