[sdiy] Re: P5

[Roy J. Tellason]

On Monday 11 July 2005 04:15 am, Oakley Sound wrote:
> > I'd check the voltage of the wiper with the pot centered.
>
> Done that. And gone further into the auto-tune circuit too. There's a
> switching circuit that locks out the tune pot and the pitch bender when
> in auto-tune. But the voltage of this circuit does not waver with the
> pots centralised when the switches are closed again after the auto-tune
> has finished its run. There's something else common to all VCOs causing
> them to be offset when not in the tune routine. For now, it has me
> stumped.
>
> One possibility is something that JH mentioned on the AH list many years
> ago about the S/H timing. This is different in the auto-tune routine as
> it is in normal operation. It could be that I have excessive droop [!!]
> somewhere in there. But on all VCOs... mmm, very odd.
>
> I'm sure I'll get there. Need to get the humming transformer fixed first
> though.

Could you have a power supply problem,  perhaps?  That humming transformer may 
be an indication of something...

Too often I forget to check those,  and it comes back to bite me later 
on.  :-)