Cheap Dual Gate Mosfet?

Doug

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Jun 8, 2003, 8:03:17 PM6/8/03

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Does anyone know of a cheap substitute for the 40673 dual gate mosfet?
The 40673 is going for $8 or better if you can find them at all.
Thanks, Doug N0WVA

Michael Black

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Jun 8, 2003, 11:00:10 PM6/8/03

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I think Dan's Small parts still has some various types of MOSFETs.
http://www.fix.net/dans.html

A few years back, I found at a dollar store RF preamps for the FM
band, intended for auto use. Curious, I bought one and brought it
home. It had a MOSFET inside, I think a 3N200. Since it was only
a dollar, I went back and bought all that were left. I don't know
if that was a lucky find or not, though the specific unit looked
like something Radio Shack was selling. I've yet to get around to
trying them, to see if they are any good.

I think some TV tuners use MOSFETs, though I'm not familiar enough
with them to know how common or in what tuners or TV sets. Considering
it's easy to pull tuners out of TV sets waiting for the garbage, that
might be a source of MOSFETs.

I have a number of Delco digitally tuned car radios, and they have
a significantly looking transistor for the FM RF stage. I guess
I didn't bother tracing the circuit because it seemed a shame to
even consider scrapping them. But if it is a MOSFET, that might
be a way of getting some MOSFETs, since these are pretty common radios
and I've picked them up for five dollars at garage sales and even found
some in the garbage.

Other than that, I can't think of common consumer items that used MOSFETs,
limiting their availability in scrap equipment.

Michael VE2BVW

Fred McKenzie

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Jun 8, 2003, 11:15:10 PM6/8/03

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<< Does anyone know of a cheap substitute for the 40673 dual gate mosfet? >>

Doug-

In my opinion, the only reason anyone would buy a 40673, would be to have an
exact replacement.

A couple of replacements I can think of, are the 3N200 and 3N201. I think
either may have a better noise figure, but I don't know for sure if they both
can be plugged into a 40673 socket and have DC voltages and currents come out
right.

73, Fred, K4DII

Dick Carroll;

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Jun 8, 2003, 11:27:47 PM6/8/03

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Doug wrote:

ECG454 or equivalent.

Dick

Leon Heller

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Jun 9, 2003, 3:50:43 AM6/9/03

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"Doug" <janaea...@netzero.net> wrote in message
news:360a820d.03060...@posting.google.com...

> Does anyone know of a cheap substitute for the 40673 dual gate mosfet?
> The 40673 is going for $8 or better if you can find them at all.
> Thanks, Doug N0WVA

BF981 is easy to get here in the UK, made by Philips. I think it's been
replaced by the BF991.

Leon
--
Leon Heller, G1HSM
leon_...@hotmail.com
http://www.geocities.com/leon_heller

Richard Heindel

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Jun 9, 2003, 10:33:52 AM6/9/03

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The NTE222 is a direct replacement for the old 40673 also, the NTE454 will work.
Not sure of the price but since I have 6 ea. they couldn't have been too much.

73
Richard WB8KRN

"Doug" <janaea...@netzero.net> wrote in message
news:360a820d.03060...@posting.google.com...

Laura Halliday

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Jun 9, 2003, 12:33:08 PM6/9/03

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"Leon Heller" <leon_...@hotmail.com> wrote in message news:<bc1e8j$hfm$1...@sparta.btinternet.com>...

> "Doug" <janaea...@netzero.net> wrote in message
> news:360a820d.03060...@posting.google.com...
> > Does anyone know of a cheap substitute for the 40673 dual gate mosfet?
> > The 40673 is going for $8 or better if you can find them at all.
> > Thanks, Doug N0WVA
>
> BF981 is easy to get here in the UK, made by Philips. I think it's been
> replaced by the BF991.

I bought a dozen BF981s at Cricklewood Electronics the
last time I was in London. My usual mail-order source
for European components is Barend Hendriksen, whose web
page lists all the usual suspects.

The 40673 is a collector's item now, and attracts
collector's item prices...

Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89lg pied a terre..."
ICBM: 49 16.57 N 123 0.24 W - Hospital/Shafte

Eamon Skelton

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Jun 9, 2003, 10:54:18 AM6/9/03

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Metal can:

3N201 or 3SK45

Plastic package:

BF961, BF981, BF988, 3SK88.

73, Ed. EI9GQ.

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Michael A. Terrell

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Jun 12, 2003, 3:29:36 PM6/12/03

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I used to buy the 40673 25 at a time to repair garage door openers in
the '80s and '90s. I think they were used in the "Overhead Door
Company" brand of receiver. Lots of the old units must be coming out of
service, so you might ask people who do garage doors for their dead
receivers. The most common failure was a shorted power diode, open
electrolytic, and a burnt resistor, but the MOSFET was still good.
There is a "Overhead Door Company dealer in Ocala that i will check when
i get a chance. I salvaged piles of 6CW4 nuvistors and 6DJ8s out of the
dead tube receivers, and used them to repair a lot of old equipment,
too.
--

Michael A. Terrell
Central Florida