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Ian Greenhalgh 19th January 2019 12:54 PM

Mysterious Semelab T22PG277AXV
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Hi folks

I have obtained a number of mysterious Semelab transistors, mysterious because they are unmarked and the code written on the bag they came in does not appear to exist as I have tried googling several variations and find nothing.

Anyone got any idea what these are? My component tester identifies them as NPN transistors.

gholl 19th January 2019 01:17 PM

Have you given Semelab a call?

Ian Greenhalgh 19th January 2019 02:59 PM

I sent them an email.

Ian Greenhalgh 10th February 2019 09:15 PM

Semelab were very helpful and the information is, I think, quite interesting:


"The part number T22PG277AXV is what we would classify as a raw line and is not a sales part

A given chip set in this case the G277 die can make many different sales parts depending on how it falls within the spread of the transistor parameters and of course the way we test it .

This transistor family was from our distributed base technology very tough devices and high energy and fast switching, a typical well know device that could be made from this transistor was a BUV 28 typically 200 volt 10 amps.

I think what as happen here is that at some point the parts are as been sold as scrap parts , rather than being scrapped fully they have returned to the market place.

This is undesirable from our point of view as the devices possibly had little or no testing, we pride our self on the quality of the products we ship . I would be very interested in understanding the supply route that you obtained these parts through ?

Does the bag contain any other numbers perhaps a date code this would be in the format of two alpha characters followed by four Numeric digits (the year and the week) followed by a final alpha code. If you can provide this information I can possible trace the batch further and give you some idea as to the parts that was being targeted."

They do appear to be genuine product from us , but a very very old vintage the label on the bag is one we haven’t used for a long time circa 1990. I wonder what was blanked out ?

Not much chance of tracking the routing for these products if its gone into the market via Ebay.

We have looked at the parts we have scrapped in recent years but can find no reference to these at all.

We are very careful when scrapping parts going through authorised scrap dealer who should totally destroy the product.

We mainly manufacture for life critical applications we therefore are concerned that defective products return to the market place as fully approved parts , which of course is not desirable
So there you have it, I have a bag of scrapped parts that should never have made it into the hands of the public and the manufacturer has no idea how they did.

I guess this story is appropriate to the modern phenomena of remarked 'fake' parts emanating from China, I bet that a lot of them are scrap parts that were somehow obtained out the back door of the manufacturer, perhaps without the manufacturer knowing anything about it.

Not sure what to do with these Semelab parts, I might use a few to make a headphone amp.

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