[sdiy] EMS VCS3 VCO

[René Schmitz]

Hi Yves and List,

A Happy New Year!

> I intend to build myself a clone of the EMS-VCS3 and before going into
> the hardware, I tried to simulate the behaviour of the VCO1
> with Spice3. The simulation is based on the schematics available at
> Graham Hinton's site. Unfortunately, the bloody thing doesn't oscillate 
> at all ! 
> 
> Has somebody in the list ran such Spice simulation for the same circuit
> and did it work ? Has somebody built the oscillator from this schematic
> and what are the pitfalls?

When modelling oscillators its often helpful to play with the "operating 
point" options. Turn them all off, or spice attempts to calulate an 
operating point for a circuit like a schmitt trigger, which doesn't have 
  such a thing.

Secondly, be aware that the saw to triangle convertor circuit in the 
schematic is wrong. IIRC it has to be a PNP type instead of an NPN one.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159