fake 2sk1058 -- again

[elic]

I ordered two pairs of 2sk1058 and 2sj162 for an amplifier I am building.

Amp: 300 Watt MOSFET Real HI-FI Power Amplifier | EEWeb

Mosfets: 1pair Transistor TO-247 2SK1058/2SJ162 K1058/J162 | eBay

I haven't received them yet but I noticed that the seller stated that the case is TO-247 while Hitachi's is TO 3P. I searched the internet and saw that TO 3P and TO 247 are pretty much identical. Anyone knows? Should I search for a replacement?

[KatieandDad]

Wait till they arrive.

I bought 25 x IRFP244s from E-Bay and was as woriied as you.

They turned out to be genuine.

You can build a simple SOAR test circuit to see if they hold up before you use them.

[elic]

Ho KatieandDad,
can you say what SOAR means?

[ashok]

The picture looks like the originals I have.
SOAR - Safe operating area

Katieanddad- How do you do it ?
Thanks.

[djQUAN]

last batch I bought (4 pairs) appear to be similar in the picture. except one set has the hitachi logo and the other doesn't. All came from a local store I had bought another four pairs years ago which were genuine.

I did the gate capacitance and source-drain diode check and they all appear as per the datasheet so I'm guessing these must also be genuine. I'll find out soon once the amp is built.

[elic]

There is hope :-)
I will wait till they arrive and will update this forum if they worked.
Is there a definitive way to tell if they are original?

[KatieandDad]

Most FAKES will fail well before they get anywhere near the limits of the genuine article.

If you build the MOS-FET testing circuit and, with the MOS-FET on a big heatsink, push the current up to somewhere near its limit for a short period of time.

You have to de-rate the maximum current from the specified max but the datasheet shows you how to do that.

What this will not detect is another big MOS-FET that has been re-badged.

For that you might need to measure the Vgs capacitance and compare that with the datasheet.

However, if the gain and the maximum current are good then they are probably OK.

There aren't too many fake POWER MOS-FETs out there YET, to my knowledge.

I'm sure our slimy cousins will get around to that in due course.

SLIMY as in the criminal fraternity.

[buzzforb]

THere are 50000 fake mosfet i have been looking at recently. People quoting date codes after production was halted.

[KatieandDad]

S.O.A.R.

Is indeed Safe Operating Area.

If you look at a datasheet you will find that things dont quite add up:

Lets take the 2N3055.

It has a maximum Vce of 60V and a maximum collector current of 15A.

"SO" you think, it will dissipate 60 x 15 = 900W

WRONG - It can only dissipate 150W

AND, it can only dissipate 150W when its junction temperature is at about 25 Degrees C.

As it gets HOTTER it can dissipate less, hence de-rating.

From the temperature de-rating curve in the datasheet you can work out how much power it can dissipate at say 60 Degrees. I'll guess as I don't have the datasheet open at the moment, but it might only be 60W.

Now it can still withstand 60V and it can still pass 15A BUT NOT AT THE SAME TIME.

The SOAR is where we as designers have to keep the device within its safe operating limits by limiting the current and/or the voltage as the junction temperature increases.

I know there are many more factors but I am trying to be simplistic for someone who has never heard of SOAR.

[Tekko]

Rule number one: don't buy transistors off of ebay, especially not those that are no longer produced and are known to be faked.

Buy off a reputable source life digikey, farnell, newark, mouser etc.