[sdiy] ASM-1 VCO troubles another time

[Sowa Roman]

Increase the cap value to, say, 47pF and see if something
changes.

Roman

""-----Original Message-----
""From: Fortner Florian [mailto:florian.fortner at fh-joanneum.at]
""Sent: Wednesday, April 17, 2002 12:40 PM
""To: synth-diy at dropmix.xs4all.nl
""Subject: [sdiy] ASM-1 VCO troubles another time
""
""
""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
""
""
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