Microalloy Transistors

[keith3d]

Does anyone know anything about microalloy transistors (MATs)? I know they were heavily promoted and sold by Clive Sinclair in the 1960s, and I also know that the story about them being Plessey rejects that Sinclair and his wife tested and labelled. But was there really anything special about them? Back in the 60s, I wanted to build some tiny receivers using some of the circuits Sinclair published, but I could never afford his MAT transistors and, of course, he made it clear that no other type would work! Was I misled? Would I have been OK with OC44 or even "white spot" transistors?

What's brough this to mind is that I've started to sort out my collection (probably accumulation would be more accurate) of old electronic components, and this afternoon I came across three brand new MAT120 transistors, still in their packets, complete with an information sheet from Technical Suppliers Limited, which I'm guessing was a company in which Sinclair had an interest. I probably bought these some time in the 1980s or 90s.

Out of curiosity, I tested a couple of the MATs - one had an hfe of 8, the other and hfe of 23. That doesn't seem too impressive to me, but I notice that the information sheet quotes a common emitter current gain of just 25 to 75, which doesn't really stack up with the claim on the other side of the sheet, which says, "very high gain"!

Incidentally, I also found a couple of SB078 surface barrier transistors, but these are in "used" condition. I'm reluctant to put them on my tester, because it uses a 9 V supply and I vaguely remember that the maximum for these was about 5 V. Strangely, I can't find any data for the SB078 on the web. The only reference that comes up is to a kit from Henry's Radio that apparently used them.

Finally, if I've posted this in the wrong forum, please let me know. I only joined yesterday so I'm still finding my way around.

Thanks for reading this!

Keith

[Pat Pending]

The Sinclair miniature MW receivers would all have worked with early Mullard OC xxM transistors, the gain in those examples does seem poor but then they have probably been knocking around for forty odd years, and no transistor of that vintage was great in that respect . The technology used in the metal alloy transistors was I believe developed by Philco in the US and for their time were a quantum leap in performance, some examples having ft sufficient to allow their use in vhf radio sets. Sir Clive did have a gift for talking up his products, and spoke of the mat transistors as if they were produced at his own premises.  A couple of years ago I called in at J Birketts in Lincoln and was amused to see that they had packs of ten mixed types of mat's on sale for a pound.....

[Refugee]

They were not special apart from the printed number on them.
Like the spot ones they were just tested rejects.
I used to buy them unmarked and test them on my home made test set with a range of 5 collector currents to choose from at a fixed VCE.
I still have the test set and used it about a year ago on some power transistors with an external bench power supply to extend the current to a couple of amps or so.
Just don't fix a transistor tester that is not broke.

[Murphyv310]

Hi.
I have a few MAT100 and 101's. They test OK but from what I can remember they were pretty much a mixed bag, some good some not so good.
Perhaps one day I'll give them a proper try out.