Re: Anonymous Semiconductors - Help!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

As you may have noticed, most manufacturers don't put data sheets for
obsolete or discontinued devices on the web (no economic incentive to do
so...).  Start collecting those old databooks.  (This is a big problem for
those of us in the spacecraft business.. Spacecraft tend to get built with
"mature" parts with a long history, and then, if it is for deep space, it
might take 10 years to get where it is going, so if you have some question
about how something works...)

Some manufacturers, particularly for simple devices in a series, use part
numbers with a pattern (big SCRs fall in this category..), and even though
the part you have isn't listed, you can figure out what the relevant specs
are.

A lot of times it is a "house number", i.e. a custom part number for a
fairly standard device produced for a volume customer.  Probably your best
bet is to build some little test sets to actually measure the parameters of
interest for  the devices.

Measuring forward gain/transconductance for FETs and transistors is fairly
easy.  Switching times, the same.
Voltage limits are a bit tougher, but also doable (check out designs for
curve tracers), the key being limiting the device dissipation when you
exceed the limit. Generally speaking exceeding BVceo (for transistors) for a
short time and by a small margin doesn't do much damage.

Figuring out max power dissipation is a bit tougher...   You can get there
somewhat indirectly by figuring out how to measure junction temperature
(i.e. diode forward voltage drop), then dissipating a known amount of power
and measuring the temperature rise to get the thermal resistance.  Then,
figure something like 150 degree C max Tj..


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, December 31, 2001 4:43 PM
Subject: Anonymous Semiconductors - Help!


> Original poster: "Matthew Smith by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <matt-at-kbc-dot-net.au>
>
> Hi All
>
> I salvage a lot of old components, especially power transistors,
> 200/300V electrolytic caps, etc., for my "goodies box".
>
> The problem that I find is that the numbers stamped on transistors thus
> acquired tend to draw up blanks on Internet searches, even when the
> manufacturer is identifiable.  (This includes the manufacturers' web
> sites.)
>
> Can anyone point me to an online resource where I can find out what
> exactly I have got?  From markings on the boards, I know that I've got
> MOSFETS and bipolars, some looking pretty meaty and thus suitable for
> SSTC experimentation.
>
> I also come across lots of ferrite-cored inductors - the type that can
> be rewound.  Anything vaguely safe around that can disolve the gunk with
> which these tend to be glued together?  If it doesn't dissolve the
> bobbin at the same time, so much the better ;-)
>
> Any suggestions welcome.
>
> Cheers
>
> Matthew Smith
>
>
>