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fake mosfet!

Hello group,

I am repairing a failed JRL-2000F HF linear amplifier. It employs 48 mosfet (2SK408 and 2SK409). The symptom was power unit shutting down because it detected a short circuit in the amplifier boards. I knew all mosfet had been previously replaced. I started disassembling the power amplifier boards looking for the short (which looked like a diode drop on a multimeter, from positive to negative only). I first removed all heatsink to exclude any short on the tabs to ground. Nothing, the "short" was still there... then I tried to power a board with a 60A power supply, thinking that the failing component would release its smoke, well, no smoke at all, fortunately not even from my poor power supply. Then I removed one of the mosfets and I checked it off circuit and noticed I could measure a diode drop from drain to source, right, I checked on the datasheet and they're supposed to have this diode.... WAIT! what direction is this diode? Yes, you guessed, the diode was in the WRONG way. What I have is a lot of FAKE 2SK408 and 2SK409. Looking at the datasheet, pinout for the 2SK408 is G-S-D and for the 2SK409 is D-S-G, the fake ones have all G-D-S pinout, no matter if they have the K408 or K409 marking, all have the hitachi logo printed on the case, they look indeed the right thing and they're indeed a kind of a mosfet, I could open the channel with a few VGS volts. Did anyone ever heard of fake components? Unfortunately I don't know where the owner of the amplifier got the replacement "new" mosfets.

Regards

Francesco IZ8DWF

Reply to
francesco.messineo
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Faked parts are not uncommon, take a look here:

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Jorgen dj0ud

Reply to
Jorgen Lund-Nielsen

Reply to
Jeroni Paul

hi, dear freind, i would like to know if you still need 2SK408 and

2SK409,we have stock to offer,

this item(2sk409 2sk 408) is very absence in the market,and i think perhpaps some lawless seller to make fake to sell.

last year ,we have a customer in AR. they also got fake 2sk409 2sk408 in their locate market, so i am not surprised what your happend.

we have especialized in electronic over 19years.most of our customers of china distribute repairs line and graduate school ,we also have plenty of overseas customers,pls find our reference in enlosed documents. because we have many years experience for repairs line,so we can convince you of our service,we hope to establish long-term trade relationships with you. since 2001,we became a member of ERAI.

pls give me e-mail if you need any component, sepeciately stop-producted,hand-find,

e-mail: snipped-for-privacy@gmail.com MY msn: st snipped-for-privacy@msn.com skype : michaelvisual

huandong electronics ltd.

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Reply to
michaelchina

Brand of the fake is indeed Hitachi as the original one, also it's very difficult to wire "correctly" 48 mosfets if the original pcb and heatsink are drilled for the standard pinout reported on the only datasheet I've been able to find; plus it doesn't mention any alternative pinout. I believe these mosfet are now obsolete but since they have been used in some expensive equipment there're always outlaw manufacturer that just produce cheap fakes as it wouldn't be very profitable to make real clones. I really doubt Hitachi would allow the use of a type code (and its logo too) if the manufacturer doesn't follow the original specs of the part.

regards

Francesco IZ8DWF

Reply to
francesco.messineo

Counterfeit components are rife these days.

Buy your parts from a manufacturer authorised supplier.

Graham

Reply to
Eeyore

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