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Old 1st December 2012, 08:04 PM   #471
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Default Possible fakes from MCM?

Greetings,

I've been trying to repair a Denon DRA-600. I've gone through several sets of output transistors. I finally opened one up. This is supposedly a 2SA1106 purchased from MCM a few months ago. The die is only 1.3 mm on each side (1.74 square mm). I had the power supply current limited to about 300 mA (although there were some capacitors that could have dumped current) and this and its complement blew.

Do you think this is a fake?
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Old 24th December 2012, 08:33 AM   #472
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Default 2SJ74BL

I got four 2SJ74BL jfets from an eBay HK seller that are very strange.
I tested them for Idss and with great surprise at only -6Vdc (the first battery at hand, a not fully charged 9V) it was over -100mA. I tried one at -9V and it exploded. Well, I think there's no doubt they are not 2SJ74BL, I'm going to ask refund.
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Old 24th December 2012, 11:55 AM   #473
AndrewT is offline AndrewT  Scotland
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and report them for attempting FRAUD !
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regards Andrew T.
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Old 24th December 2012, 12:18 PM   #474
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I was the last of a long line of people that purchased that "2SJ74BL". Nobody placed a negative feedback or comment. Maybe none tested them. The seller has not replied to my remarks yet.
The exploded at -9Vdc.
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Old 24th December 2012, 12:25 PM   #475
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m.massimo, your's J74 are fakes. Front surfaces are sanded down, they are too thin.
Originals should have glossy surface and different font type.
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Last edited by stormsonic; 24th December 2012 at 12:28 PM.
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Old 24th December 2012, 12:42 PM   #476
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Quote:
Originally Posted by stormsonic View Post
Front surfaces are sanded down, they are too thin
Thank you for your comment. I've many original K170, but I didn't noted that difference. Good point. I've just taken some measures. K170 are 3.87mm, these fakes are 3.47mm, Toshiba states 4.1 as maximum.
There's no doubt that are fake with 100mA Idss at 6Vdc!
They sold about one hundred of them and nobody reported something strange.
I'm very surprised at it. Anybody tested them before inserting in a circuit?
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Old 24th December 2012, 03:47 PM   #477
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Quote:
Originally Posted by m.massimo View Post
K170 are 3.87mm, these fakes are 3.47mm, Toshiba states 4.1 as maximum.
There's no doubt that are fake with 100mA Idss at 6Vdc!
I'm guessing that you forward-biased the G-S or G-D junction due to different pinout on the fakes. They could be re-marked j175 or similar p-channel switches, which are much cheaper.

You can try measuring Ciss across G-S with a smart SMD tester like the Mastech MS8910. All my original Toshiba 2sk170 are within / - 20 % of the published spec. The fakes tend to have very low values like 5 pF because of the smaller die area, but this is not conclusive. Some of the re-marks may be large-die devices.
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Old 31st December 2012, 05:31 AM   #478
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Default fake transistor from china

Nowadays, most fake transistors were manufactured in the CHINA, I've bought hundreds of different types and differ part of transistor. All fake and not meet Bvceo, and PD not as stated.
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Old 31st December 2012, 03:59 PM   #479
LAJ is offline LAJ  United States
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The last semiconductor I purchased from MCM was a fake.
Their management is aware of the problem.
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Old 5th January 2013, 02:28 AM   #480
DaveG is offline DaveG  United States
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I'm adding a few photos of obvious fakes to this thread that I ended up with awhile ago for reference.

They all looked bad right out of the bag, and after some close inspection I found several with remains of the original markings. I went through my parts and just happened to have some of the original parts on hand for comparison. These were apparently sanded down.
Sloppy work by sloppy people.
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