Russell McMahon wrote:
>
> > >Please describe the circuit !


I'm guessing it can be done with 2 caps, and 2
resistors so under the right conditions the resistance
and capacitance of the breadboard would be enough to
make it work...

Like this;

+v -----*-----------------------------------
        |
        |               hi-gain NPN
        R1  10k ?
        |
        *-----R2--------*-----,
        |   20 ohms(!)  |     |
        |               C     |
        *-------------B       |
        |               E     C2 30pF(!)
        C1 60pF?        |     |
        |               |     |
        |               |     |
gnd ----*---------------*-----*--------------

I had some things *like* this oscillating when I was
testing capacitor dump systems during design of my
2-tran Black regulator. They rely on one cap being
dumped into another via *some* resistance.

In the case above the (!) parts are the capacitance
of the breadboard strips and the significant resistance
of the 2 breadboard spring contacts between C1 leg
and collector leg of Q1. Which explains why the spice
model didn't oscillate. :o)
-Roman

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