Hi Ken,
Thanks for your quick reply.
I checked and rechecked all the components and I don't see any mistakes.
Each section has two 557 transistors and one 547 transistor. I went with the orientation on the silk screen which is what is in the schematic. All the voltages components check as to the schematic.
The frequency pot is a 100K set between +15 and -15. I added the 150K resistor inline with the wiper. The voltage at pin 1 of the TL072 varies between -.13 and +.13 depending on the pot settings. The Voltage at pins 5 of the 3080 is -5 (on both) with -2 at pin 6.
I switched the TL072 to no effect. Note that the voltage on the pot after the 150K res is +/- 6 depending on the pot poss.
I get a signal out of the module very low for LP and HP ( about .1v) and higher for BP and Notch (about 5v), the distortion works. but the frequency pot has no effect.
What is the CVSN for ? I did not connect it as I assumed it was optional for centring the freq pot.
Any ideas?
Robert
Thanks for your quick reply.
I checked and rechecked all the components and I don't see any mistakes.
Each section has two 557 transistors and one 547 transistor. I went with the orientation on the silk screen which is what is in the schematic. All the voltages components check as to the schematic.
The frequency pot is a 100K set between +15 and -15. I added the 150K resistor inline with the wiper. The voltage at pin 1 of the TL072 varies between -.13 and +.13 depending on the pot settings. The Voltage at pins 5 of the 3080 is -5 (on both) with -2 at pin 6.
I switched the TL072 to no effect. Note that the voltage on the pot after the 150K res is +/- 6 depending on the pot poss.
I get a signal out of the module very low for LP and HP ( about .1v) and higher for BP and Notch (about 5v), the distortion works. but the frequency pot has no effect.
What is the CVSN for ? I did not connect it as I assumed it was optional for centring the freq pot.
Any ideas?
Robert
--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> It is probably a construction error cause by missidentified parts - the sort
> of thing that would cayse the same mistake to be made twice. Check that you
> have the correct transistors in each expo converter. There is an NPN an a
> pair of PNP in each. Get one in the wrong spot, and it won't work. Also
> check power directly at the chip's power pins. Make sure any CV or pot
> change results in a voltage change at Pin 1 of the corresponding TL072.
> Check you haven't cooked your LM3080s.
>
> Ken
>
> >Hello,
> >
> >I am having a problem with the CMOS filter. The frequency pot on either of
> the filters has no effect. The CV's input also have no effect. I have set
> the trimmers to the minimum setting and still no effect. A saw tooth wave at
> the input gives a saw wave at the HP and Notch but nothing at the LP or BP.
> The distortion gives the desired effect of turning the saw into a distorted
> saw on the scope. The voltages are all good + - 15 and -5 are at all the
> correct spots. Both sides of the Dual filter behave the same way?
> >
> >Any ideas what may be wrong? I have tried the frequency pot (CW and CCW)
> set at O /+15 and -15/+15 doesn't make any difference.
> >
> >Thanks
> >Robert Gerard
> >
> >
> >
> >
> >
> >------------------------------------
> >
> >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/>
>