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cgs29 wave multiplier problem

cgs29 wave multiplier problem

2012-11-13 by nikmisnikmis

Hello,
I was wondering if anyone might give advice on my cgs29 Wave Multiplier build. It's a Version 1 Rev 2 board. I got it together this weekend, and I thought it was working correctly on the first power up. Now that I have played with it a bit, I realize there is something probably wrong, maybe. The grinder and lockhart sections are working perfectly. The main folder section is doing something, but its not what I think its supposed to be doing.

The main folder section triangle and pulse outputs are identical. They are both outputting what I think is a 'squared' output. I don't have an oscilloscope, but with a fixed voltage or an lfo on the triangle input, the output switches between +/- 15 volts, nothing in between.

The pulse width modulation section doesn't effect the output. The offset and folds cv sections are working correctly, which is what tricked me at first. The output voltage just switches between +/- 15 volts, but it does fold the original waveform, so that switching occurs at different points of the waveform. if that makes any sense

All the ICs are getting correct voltages and my wiring seems correct. I have probably done something really stupid. The only other thing is, I am using a CA3080 instead of a LM3080, but I think that doesn't matter.

Can you guess what I did wrong?
thanks

Re: cgs29 wave multiplier problem

2012-11-13 by sasami@hotkey.net.au

CA3080 is the same chip as LM3080.

You have a problem with a feedback resistor somewhere. One of them is too
high a value, or has a bad joint. It could be the 100k around IC5a, any of
the 10ks on IC5b,c,d, and possibly, but not likely, the 10k around IC4c. I
would start with the 100k and work backwards along the chain.

Ken
Show quoted textHide quoted text
>The main folder section triangle and pulse outputs are identical. They are
both outputting what I think is a 'squared' output. I don't have an
oscilloscope, but with a fixed voltage or an lfo on the triangle input, the
output switches between +/- 15 volts, nothing in between.
>
>The pulse width modulation section doesn't effect the output. The offset
and folds cv sections are working correctly, which is what tricked me at
first. The output voltage just switches between +/- 15 volts, but it does
fold the original waveform, so that switching occurs at different points of
the waveform. if that makes any sense

_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: cgs29 wave multiplier problem

2012-11-13 by sasami@hotkey.net.au

Also check the input resistors along this chain. A too low a value or a
short would also have this effect.
Ken
Show quoted textHide quoted text
>CA3080 is the same chip as LM3080.
>
>You have a problem with a feedback resistor somewhere. One of them is too
>high a value, or has a bad joint. It could be the 100k around IC5a, any of
>the 10ks on IC5b,c,d, and possibly, but not likely, the 10k around IC4c. I
>would start with the 100k and work backwards along the chain.
>
>Ken
>
>>The main folder section triangle and pulse outputs are identical. They are
>both outputting what I think is a 'squared' output. I don't have an
>oscilloscope, but with a fixed voltage or an lfo on the triangle input, the
>output switches between +/- 15 volts, nothing in between.
>>
>>The pulse width modulation section doesn't effect the output. The offset
>and folds cv sections are working correctly, which is what tricked me at
>first. The output voltage just switches between +/- 15 volts, but it does
>fold the original waveform, so that switching occurs at different points of
>the waveform. if that makes any sense
>
>_______________________________________________________________________
>Ken Stone sasami@... otherunicorn@...
>Modular Synth PCBs for sale <http://www.cgs.synth.net/>
>Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: cgs29 wave multiplier problem

2012-11-13 by nikmisnikmis

Wow, spot on! I feel dumb for not seeing it before. 10k resistor on IC5b was not connected.

Thank you so much!
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> Also check the input resistors along this chain. A too low a value or a
> short would also have this effect.
> Ken
>
> >CA3080 is the same chip as LM3080.
> >
> >You have a problem with a feedback resistor somewhere. One of them is too
> >high a value, or has a bad joint. It could be the 100k around IC5a, any of
> >the 10ks on IC5b,c,d, and possibly, but not likely, the 10k around IC4c. I
> >would start with the 100k and work backwards along the chain.
> >
> >Ken
> >
> >>The main folder section triangle and pulse outputs are identical. They are
> >both outputting what I think is a 'squared' output. I don't have an
> >oscilloscope, but with a fixed voltage or an lfo on the triangle input, the
> >output switches between +/- 15 volts, nothing in between.
> >>
> >>The pulse width modulation section doesn't effect the output. The offset
> >and folds cv sections are working correctly, which is what tricked me at
> >first. The output voltage just switches between +/- 15 volts, but it does
> >fold the original waveform, so that switching occurs at different points of
> >the waveform. if that makes any sense
> >
> >_______________________________________________________________________
> >Ken Stone sasami@... otherunicorn@...
> >Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> >Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
> >
> >
> >
> >------------------------------------
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >Yahoo! Groups Links
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>

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