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.

I do not possess all the transistors and diodes described below, in fact I am seeking some of them. It is noted in the text where I am seeking examples of any particular type: if you have some for sale or exchange, please


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 germanium junction diode
  • AC113 AC114 and AC115 germanium junction transistors
  • AC154 to AC157 germanium junction transistors
  • AC165 to AC169 germanium junction transistors
  • AC176 and AC177 germanium junction transistors
  • AD140 and AD149 germanium power transistors
  • BA116 and BA126 silicon double diodes
  • BY100 BY101 BY105 BY114 BY124 and BY130 silicon diodes

wanted ASY transistors However I believe that they manufactured at least one other range, ASY82 to ASY89. These must be later than 1966. If you know where I can find any of these, or have data for them, please


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.

I am seeking the following transistors by Thorn-AEI, with any of their brands:

  • AD140(branded Mazda or Thorn or Brimar, not Mullard or others)
  • any ASY type such as ASY82 (branded Mazda or Thorn or Brimar)

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


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:

  • pre-amplifier AC156
  • amplifier AC113
  • driver AC165
  • complementary output AC154 and AC157
  • bias compensating diode AA120

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.


power transistors

Thorn-AEI made two 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.


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 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






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