AW: [sdiy] Zener-oscillators

[eq927 at freenet.carleton.ca]

Accidentally made a "reverse-breakdown" VCO (distant past...1976?) when 
using a 2N5449 NPN transistor (inexpensive and readily available at the 
time) as a reset switch for an op amp integrator in a linear VCO. I was 
surprised when the circuit worked without having a comparator chip 
installed... Went on to make a triple linear VCO board using this method 
- tracking was terrible... but all the 2N5447 I tried (around 10 of 
them) worked in the circuit - all broke down with reverse 15 to 20 volts 
between collector and emitter with base open. I have not tried this 
since - better results may be possible. A DIAC (2-terminal switch used 
for triggering SCR's) also works - the DIAC can be hooked up either 
direction (almost a solid-state neon bulb).
Regards, Mike