[sdiy] Crap.. I need help with my x0x

[Jeff Farr]

What I should say is that the output of the VCF never matches what is coming
in from the VCO. I'm willing to believe that the cutoff has a low maximum
and relies on the envelope modulation, although I remember being able to get
bright buzzy sound out of a 303 just by turning up the cutoff. As it is now
even with the env mod at max the signal is muted. The decay defiantly
doesn't work at the moment either but what I really need some help with is
the VCA, I still can't figure the 6110 out nor the fact that the pins read
either 5V or ground except pin 9 which shows 12V. The schematic confuses me
here, there are multiple connections to the 6110 marked as pin 3 etc and
there are some pins with more than one marking. I've just double checked my
de-fluxing and have been going over the joints for awhile now. All are clean
and shiny.

On 10/26/05, gregory zifcak <zifcak at hotmail.com> wrote:
>
> based on my limited experience with a 303, a couple vague points:
>
> "clean" saw or square might not be the right shape to look for here.
>
> the filter cutoff should not track with the VCO, and has a relatively low
> maximum cutoff (500 hz, i think i may have read?) without the envelope
> modulation.
>
> also, it is possible that the envelope is supposed to lower the overall
> cutoff; i've read that it modulates the filter first above, then below the
> cutoff setting. however, at the beginning of the envelope the cutoff
> should
> go quite high; if i remember my experience correctly, with cutoff and res
> (for hearing purposes) set to max, it should be possible to use the
> envelope
> to make the filter open above audible frequency range. possibly not with
> envelope modulation set to max though, if it's in fact lowering the
> overall
> frequency.
>
> as far as envelope time, i would guess it's supposed to vary between about
> 50 and 1000 ms.
>
> i don't know anything about the VCA, sorry. i suppose you've seen the
> ba6110
> dip datasheet out there and that it's no help. once i start working on
> mine
> maybe i'll have some insight.
>
> 303 gurus correct my mistakes please,
> greg
>
>
> >The assembly in general has been going well, no screw-ups about placing
> the
> >wrong components or messing up the orientation. I've even gone over the
> >part
> >list for each section twice now, carefully checking that what was in my
> >board was correct. The VCO works fine and the VCF works.. but rather
> >poorly.
> >It seems that even with the cutoff all the way up the signal is being
> >filtered, and the cutoff doesn't track along with the VCO, even so I
> can't
> >create a note that's low enough to see a clean saw or square. Turning the
> >env amount knob up causes the cutoff to drop, perhaps this is normal?.
> >Again, I've checked *very carefully* *twice* *each* component and it's
> >orientation using a magnifying glass and a bright halogen lamp. They are
> >all
> >correct, each resistor, capacitor and transistor, and they were all
> correct
> >the first time I soldered them in. Now, leaving the VCF behind the
> envelope
> >appears to be working as proper. Measurements at D35 and 36 agree with
> what
> >is listed in the fab manual and the VCF will respond to triggering the
> >envelope, but I'm doubtful that the decay is working as it's quite snappy
> >at
> >either end of it's range. Still, I pressed on and assembled the VCA and
> >here
> >is where things get discouraging. No signal at all while performing the
> >test
> >from the manual. In fact I don't understand why I would be using R10 to
> >generate a pulse when before I was using R3 (using R3/R146 the VCF will
> >respond). Measuring R10 certainly didn't show 10V, and it was part of the
> >pre-assembled USB section, so I'm wondering if this is an error in the
> >manual. Now, I would like to know if I can test the difference between
> the
> >VCA being triggered and the VCA working. In fact the signal from the VCF
> >disappears after C21 and R121, after that all I can read is 5V, almost
> >everywhere in the VCA circuit. I need some advice on this. I don't
> >understand how the filter works well enough to break it into an input
> >stage/
> >output stage and definitely don't know what I would want to see anyway
> and
> >the VCA has me completely lost due the the mystifying BA6110 in 9 pin SIP
> >for which I can't find a datasheet.
>
>
>
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