Electronics > Beginners

Fake 2n3055's

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MagicSmoker:
It's not just the TO-3* package that is obsolete, so is the double-diffusion fab process that made it. Modern "2N3055" are almost certainly made with the epitaxial process which generally produces a faster transistor (due to lower junction capacitance) but one that is also less robust. Then again, if it's a cheap knock-off from China then it might very well be a 2N2222 die in a TO-3 package...


* - now called TO-204AA, for dog only knows why.

T3sl4co1l:

--- Quote from: MagicSmoker on June 26, 2019, 10:39:17 pm ---It's not just the TO-3* package that is obsolete, so is the double-diffusion fab process that made it.

--- End quote ---

The original fabs died in the 80s, AFAIK; they've been epitaxy since then.  Which means the average 2N3055 you get, will exceed its spec by 2-10 times or better, and you'll never know in which parameters until you test them a lot at a time.  Or maybe you get some ancient relics! :palm:

If you must have old fashioned packages, I wouldn't recommend anything older than, say, MJ15022 or the like.  If you must have BJTs, newer On Semi parts have excellent specs, and will most definitely deliver the power and SOA they claim.  They aren't at all expensive, considering how much faffing with alternative sources you are saving in the process!

Even better still is using FETs in an SMPS, but that is a more advanced topic so I won't complain further in that direction. :D

Tim

cvanc:
Interesting discussion.  Somewhere around here I have a few marked '2N3055H' from decades ago.  I never knew what the H signified - homotaxial, perhaps?  I remember they cost a bit more than the non-H version at the time.

MarkF:

--- Quote from: Yansi on June 25, 2019, 09:15:03 am ---Problem is, even the genuine ones are absolutely useless these days!!! The so small barely visible silicon die coupled with the steel case with zero to no good thermal conductivity makes the transistor useful only as a paperweight and even that would not be good enough.

Ditch 2N3055,  use TIP3055 (TO247). That at least, when kept within reasonable limits, works wonders.

--- End quote ---

Slightly off topic question:
Does anyone know where in its life-cycle the TIP-3055 is for new designs?

rsjsouza:

--- Quote from: MarkF on June 27, 2019, 01:37:56 pm ---
--- Quote from: Yansi on June 25, 2019, 09:15:03 am ---Problem is, even the genuine ones are absolutely useless these days!!! The so small barely visible silicon die coupled with the steel case with zero to no good thermal conductivity makes the transistor useful only as a paperweight and even that would not be good enough.

Ditch 2N3055,  use TIP3055 (TO247). That at least, when kept within reasonable limits, works wonders.

--- End quote ---

Slightly off topic question:
Does anyone know where in its life-cycle the TIP-3055 is for new designs?

--- End quote ---
That depends on the manufacturer. TI's TIP3055 (the original) was obsoleted a long time ago, while ON and ST still have them.

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