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

wrote:

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

Faked parts are not uncommon, take a look he

http://sound.westhost.com/counterfeit.htm

Jorgen
dj0ud

Some brands offer versions with another terminal ordering and another
letter suffixed on the part number. Did you try to wire it correctly?

wrote:
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

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:

MY msn: skype : michaelvisual

huandong electronics ltd.







Anonymouswrote:
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


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On 5 Apr, 01:02, "Jeroni Paul" wrote:
Some brands offer versions with another terminal ordering and another
letter suffixed on the part number. Did you try to wire it correctly?


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

wrote:

What I have is a lot of FAKE 2SK408 and 2SK409.

Counterfeit components are rife these days.

Buy your parts from a manufacturer authorised supplier.

Graham