I have had several transistor types fail over last 13 years
No failures with the Opto type circuits
No keying problems
( W1GEE Opto units )
U got lucky
others mileage may vary
stick with the Opto units
My 2 cents
N6KI
On Tue, Nov 11, 2008 at 12:08 AM, Art Boyars <art.boyars@verizon.net> wrote:
> N6KI said "Be sure the one U buy uses an Opt Coupler typr device and not
> descrete transistor(s) - The Optos are far more reliable !!!"
>
> Gee, the 2N398A germanium PNP and the whatever NPN used in the original
> implementation of the "K3KU circuit" for keying pos or neg have been in use
> for over 30 years w/o failure. They may well pre-date optocouplers AND
> computer keying.
>
> I still have a few 2N398A's if anybody wants to build the circuit, though
> the MPSA92 used by Logikey in their CMOS4 and by MFJ in their 490 would work
> fine. (Note that Logikey and MFJ both use it as a separate neg keying
> output, not the K3KU circuit.)
>
> 73, Art K3KU
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