[sdiy] Nostalgia :)

[Roy J. Tellason]

On Saturday 26 March 2005 09:25 pm, Glen wrote:
> At 10:12 AM 3/26/2005 , Kevin Lightner wrote:
> >http://www.swtpc.com/mholley/PopularElectronics/Feb1971/PE_Feb1971.htm
> >
> >(one of those simple URLs that's sure to elicit comments from the old
> >timers ;-)

Heh.  What was really a hoot was that digital counter board.  I actually built 
a counter and sold it to a guy that later on had me in some industrial 
situations,  back around 1974 or so.  I don't think it was the same board 
(used 7490 instead of the chip they used) but it sure looked like that!

> Mmm...  UJT oscillators...
>
> Can you still get UJTs anywhere?

If not,  it's easy enough to make one with a complementary pair,  
cross-connected.  Or an SCR,  for that matter (same circuit).  Look for a web 
site for "4QD",  I think that's where I found it.  One transistor's base will 
be the "emitter" of the UJT,  the other one needs a couple of resistors to 
set the trigger point,  think of it as a "PUT".