[sdiy] ASM-1 VCO troubles another time

[>>>marjan<<<]

> I've built the VCO on a selfmade PCB, and the Output of the Integrator
> (CA3140) gives a strange high-frequency sawtooth (between 70 and 160 kHz
> with a magnitude of ~1V and an offset of 4.5V), the Voltage on the gate of
> the FET (I used a 2N3819 which has a slightly higher rdson) is a kind of
> "rounded" rectangle, not spikes. The cool thing is, that when I touch the
> 18p Cap (C3) with my finger the freq. drops to the desired 8-10kHz and the
> FET voltage becomes the spike-waveform. Any ideas what this could be? I
> already double checked the board and defluxed it.

RC constant's too small, try 33 or 47pF cap instead 18p


-- 



marjan


me    : Marjan Urekar
e-mail: urekar.m at eunet.yu
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