Issue resolved.
I had to go open it up to swap some of the tact-switches and "middle-pieces" , and decided to look into this issue again.
I found a similar thread about a broken trace under the test point near CN-03 - I thought I'd give it a go and tested for connectivity there, and yep there was a broken trace. Soldered a wire to reconnect the points, fired it up and now the VCA can be modulated.
I'm pleased.
--- In PolySix@yahoogroups.com, Andrew Jury <andy@...> wrote:
>
> Hi,
>
> Check to make sure that the signal entering IC1 pin 3 leaves on pin4 when in
> VCA mode. If not (and I suspect not) check the switching action of IC1 on
> pin 5. If not working check the quarter comparator in IC3 at pin 5. Finally
> check the latch at IC 29. You can test most of the different logic states
> using a scope or, even better, a logic probe. This¹ll all be CMOS ons and
> offs. Tip: you can get comparative reading from the VCO mod circuit which
> follows the same lines, but on a different switching channel. (Please study
> the 367 schematic first!) Although you have had the 367 repaired I seriously
> suggest you start off doing a cold DC continuity check between the tracks I
> have mentioned. I¹d favour a break in the print over silicon in this case!
>
> Good luck and tell us all how you get on...
>
> Thanks,
> Andy
>
>
> On 01/03/2010 20:24, "djvlr" <xheigrestadx@...> wrote:
>
> >
> >
> >
> >
> >
> > Hi! First post, but let's just get right to it.
> >
> > I bought a P6 11 years ago, and it hasn't been used much, but a recent
> > interest in going hardware made me dig it out again. I'm getting it MIDIfied,
> > so I'm giving it a thorough look to get everything in top shape. I bought it
> > with the battery fix already done, and the PCB hasn't been ravaged by
> > corrosion, but the MG Mod switch will only work on the VCO and the VCF.
> >
> > A search yielded similar issues but little and incomplete information
> > regarding a fix for this, which leads to my question: is there an easy fix for
> > this and have anyone successfully sorted it?
> >
> >
> >
> >
> >
>
>
>
> [Non-text portions of this message have been removed]
>