[sdiy] Re: P5

[klosmon]

At 11:16 AM 7/11/2005, you wrote:

>I don't think so. The auto-tune routine in last revision Prophets is very
>powerful and a has a massive capture range. So if it were out of trim the
>auto-tune routine would be able to correct it. So I don't think its VCO
>tuning or scaling trims. But someone correct me if I'm wrong in this
>assumption.

That applies to the scale trims, yes;  but I'm talking about the A & B 
master offset, which slide the tuning of the oscillator sections up & down 
(while not affecting the relation of the keys to each other).

I once serviced a P5 that had this problem;  it appeared that whoever had 
last trimmed it had done so with the tune pot offcenter.  If the trimming 
of these sections is done with the tune pot (& pitch wheel) centered, and 
the rest of the controls in the "service" position, the instrument will be 
tuned to a440 with the tune pot in the centered position.  If any of those 
controls was in the WRONG position when the instrument was trimmed, it 
could result in the effect you describe.

I hope I'm making myself clear;  haven't had my requisite 4 espressos yet 
this morning.

~G


>The whole keyboard plays in perfect scale and the instrument is in
>perfect tune with itself. The internal 440Hz is perfect but the tune pot
>needs to be well off centre for the unit to be in perfect tune. Its sharp
>by about half a semitone.
>
>Interestingly the schematic in the rev 3 and rev 3.2 shows the unison CV
>being fed to the VCO 1 bank when not in auto-tune, ie switched by -TUNE
>and not be UNI. I think that's probably a typo.
>
>Tony