SV: [sdiy] FORMANT VCO restoration and improvement

[HA.Synth at t-online.de]

Hallo Steve,

is it an "old" Formant with the uA726 or a "new" one with the 3046 and 7413 or 
the "very new" one with 3046 and 4093? I am measuring an "old" Formant.

I am syncing against the regular VCO output, saw or square and i can see only 
an positiv going pulse at pin 8 of the 7413 at the falling edge. This seems 
logical for me, because it is the reset pulse for the saw. A pulse at the 
rising edge of the square makes no sense to me, becaus this must force a 
reset of the saw halfway up and double pitch.  
May be i have a wrong understanding here. I don't understand the term "sloping 
top" . Can you explain please?

Harald 

Am Donnerstag, 19. Oktober 2006 16:10 schrieb Steve Ridley:
> > I found the pulse with the method Paul suggested. It is about 40mV. I
> > think it is easier to derive sync out from an other waveform then
> > amplifying this pulse.
>
> I have a formant VCO on the bench right now, and I'm seeing a
> 140nS pulse, sloping top, 3.5v at the rising edge, 4v at the
> falling edge.
Edge of which wafeform?
>
>
> Steve