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Old 23rd January 2004, 04:59 AM   #1
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Default More Fake Transistors

Hi all,
After a few output failures recently, I decided to open some of the culprits. MJ15022/3, the size of the die is 2mm x 2mm and the wires connecting the die to the base and emmitor are as thin as hair! For comparison I opened an old 2N4399, die size 5mm x5mm and the connecting wire is a lot thicker and quite stiff.

Am I correct in assuming that the others are fake? What do I do, go back to my supplier and *****?
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Old 23rd January 2004, 05:08 AM   #2
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I'm not sure what I'm looking at, looks fake, you that is.
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Old 23rd January 2004, 09:19 AM   #3
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Hi
You are looking at the inside of the transistor with the top taken off, the dark part is the actual die of the transistor, and I coloured them in to show the size.
The two are next to each other and at the same scale so those out there who have opened a TO3 before can compare the size of the die with what they know as to be the "correct" size.
I am trying to get confirmation from others that the MJ transistor is a fake, as this is the first time I have ever opened one up.

Any comments?
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Old 23rd January 2004, 10:05 AM   #4
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Doesn't look much like a 16A 250W device, does it?

Plus....how did the top come off??? Awfully clean removal...should be a ***** to get off..

...and what's all that junk next to the die?
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Old 23rd January 2004, 10:06 AM   #5
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Unless you have removed the wires in the first one, there must
reasonably be something wrong. I can't see any wires at all on
that one, so they must really be thin as hair, as you say.
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Old 23rd January 2004, 10:07 AM   #6
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Perhaps the transistors were mis-labeled by the factory.
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Old 23rd January 2004, 10:21 AM   #7
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Quote:
Originally posted by Frank Berry
Perhaps the transistors were mis-labeled by the factory.
What would anything with such thin wires do in a TO3 at all??
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Old 23rd January 2004, 10:25 AM   #8
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High voltage, low current.
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Old 23rd January 2004, 10:27 AM   #9
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Default Top Removal

I actually reomoved three, the one MJ shown the top actually just popped off on mounting on the heatsink, hence the clean removal. The others I clamped the top in a vice, squeezed it a bit, then clamped the body in the vice and whacked the top off with a old screwdriver. Not to much effort but I was a bit angry!
The all had some white "gunk" over the die, feels like silicon sealer, and unless you clean it off you cant see the die or its size. The wires were embedded in this and they were really thin, like one strand of a copper strand wire.
I am convinced I have been ripped off twice now, cause of the three MJ150xx I checked were bought from different supplies at least a year apart. Problem is now I dont know whats good and whats not, I have a small drawer full of MJ15oxx's bought at different times and from different suppliers. They probably got them from the same distributer.
Any simple way of testing them without putting them in a amp? At least if they blow then they wont mess the rest of the amp.

DieterD
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Old 23rd January 2004, 10:28 AM   #10
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Quote:
Originally posted by Frank Berry
Perhaps the transistors were mis-labeled by the factory.
I've spent a LOT of time in Motorola fabs...it just doesn't happen.
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