Can anyone identify this transistor?

[ukcol]

This is a germanium PNP transistor with an hFE of about 30. There is a red spot to identify the collector lead and another red spot on top of the case which may identify its type or application.

Anyone know who the manufacturer was and the type?

[Cobaltblue]

Looks like one of Semiconductors Limited (Plessey) MAT series

See here

Cheers

Mike T

[ukcol]

Goodness that was a quick reply Mike.

Yes, the case looks exactly the same as the Plessey type. On my example, however, it looks like it never had any alpha-numeric markings which makes me think that the red spot is a code for a type or application.

[jimmc101]

Could be just a 'Red spot' transistor, these were manufacturers rejects sold cheaply on the amateur market.
As I remember, red spot audio, white spot RF there were also green & yellow spot and possibly red/yellow spot but I can't remember what they were for

See the last couple of paragraphs here for a little more detail.

Jim

[ParcGwyn]

I think Ediswan also used similar cases I seem to remember seeing some in the AF stages of a Murphy B385 radio.

Dave
GW7ONS

[Cobaltblue]

As far as I know only Plessey and Philco used this package

It was quite common in the 60's and even into the 70's to sell unmarked transistors and code them with a dob of paint.

These were often manufacturers rejects that didn't meet all the specs of the marked devices.

The marked transistor were beyond my pocket money in the late 60's but these were fine for most projects.

ISTR the red spot was the general purpose audio transistor white spot RF

But if varied by supplier.

Cheers

Mike T

[60 oldjohn]

Originally Posted by jimmc101

Could be just a 'Red spot' transistor, these were manufacturers rejects sold cheaply on the amateur market.
As I remember, red spot audio, white spot RF there were also green & yellow spot and possibly red/yellow spot but I can't remember what they were for

I have some here, I think Bi Pre Pack were big sellers and possibly also J Bull.
John.

[ukcol]

Thanks for the replies gents. It looks like it is a general purpose AF transistor then. The hFE of mine is quite low at 30 which is probably why it didn't get to be marked witha a type number.

[m0cemdave]

The infamous Clive Sinclair also used to sell these, presumably re-specified rejects from the Plessey factory. This was in conjunction with one of the Bernards constructor books written or edited by either Clive or his brother (Ian ?).

The Sinclair types were usually only labelled with a plastic sleeve, which would easily get lost. Part numbers were MAT (Micro Alloy Transistor) followed by a number, I seem to remember 120 and 121 and they were RF transistors with a very low maximum voltage rating, maybe surface barrier types.

It seems to have been common practice for transistor manufacturers to sell rejected batches of transistors that failed to reach the commercial specification, to companies who supplied the hobby trade. I think the better ones actually tested the devices to their own (lower) specification and labelled them accordingly. The others just sold bulk packs as "untested" leaving the buyers to sort out the good from the bad. Usually the euphemistic term "fall-outs" was used instead of "rejects".

[jim_jobe]

Some of Sinclair's MAT transistors had no markings at all. The ones in my Micro-6 receiver were just plain gold and nothing else.