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

[gregory zifcak]

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.