[sdiy] ASM-1 VCO troubles another time

[Leif]

Hi

what it might be is a faulty capacitor ?
Had similar problem on a really simple preamp based on opamps, with a 
capacitor I just touched and everything was nice, changed it for a new one 
and everything worked correctly. Haven't looked at the scematics of the 
asm-1 , just a thought.

leif

At 12:39 17.04.2002 +0200, you wrote:
>Hi list,
>
>Excuse me for annoying everbody again with ASM-1 VCO problems, but I don't
>know how to go on.
>
>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.
>
>regards,
>
>flo