[sdiy] FORMANT VCO restoration and improvement

[HA.Synth at t-online.de]

Thank you Paul,

thet worked. Now i can see the pulse. Verry narrow, about 40mV. I think it's 
easier to derive the sync out from another waveform. Instead of amplifying 
this pulse. I want to use sync out to sync another VCO.

many thanks, Harald


 Am Montag, 16. Oktober 2006 12:44 schrieb Paul Perry:
> If you have a two channel scope, then the thing is to look at a signal
> somewhere else in the circuit that will lock the scope, then that will
> stabilise the "invisible" signal (if any)for viewing on the 2nd channel.
> A classic case I do all the time, is lock the scope to the mains to see
> whether there is any mains frequency signal hidden on the supply rails.
> I'm not familiar with the Formant, but if you are talking about a pulse
> that is derived from the oscillator, then just lock to the main VCO output.
>
> It may be the pulse is "too thin" to see, in which case a 7555 pulse
> stretcher monostable might be the go. Not sure what the optimum width for
> say DIN sync is (if that is what you will use it for) but I do know that
> some things are a bit fussy!
>
> best, paul perry (melbourne australia)
>
> ----- Original Message -----
>
> >Now i want to add sync out. Therefore i wanted to use pin 8 of the 7413
> >Schmitt Trigger. Just added a source follower here. But it didn't work. I
> >can't see the pulse at the scope. Not at pin 8 nore at the output of the
> >source follower. Any ideas or help here? Maybe the pulse is to short/weak
>
> to
>
> >trigger my scope?