Regarding the first VCO, it sounds like you probably have a bad IC1, or a bad solder joint somewhere. Recheck your solder joints, and if everything looks ok, measure the voltage at pin 7 of IC1 - it should track when the incoming control voltage changes. If it doesn't, try replacing IC1.
On the second one, it's possible that the VCO is actually running, but just at a very low frequency. I had that happen on a Teezer VCO once. I'd definitely suggest replacing the TL072 - you were running it without power, so who knows what happened inside that little fellow.
Gary
On the second one, it's possible that the VCO is actually running, but just at a very low frequency. I had that happen on a Teezer VCO once. I'd definitely suggest replacing the TL072 - you were running it without power, so who knows what happened inside that little fellow.
Gary
--- In cgs_synth@yahoogroups.com, Stephen Richards <okayjustalittle@...> wrote:
>
> Hi Ken and all
>
> I'm building up the BOG panel and have done the two VCO's but am experiencing a few problems with both.
>
> One VCO is working fine apart from VC Freq pot ; seems to have zero effect on the Frequency when fed CV and when turned ; it also cuts out at the very lowest range , shorting to some sort of low droning sound.
>
> The Second VCO has no output , no change when Freq pot is moved but when FM'd , PWM'd or CV is applied the the Variable CV input , i'm getting sound from the outputs.
>
> When i checked this Second VCO , i found i had only soldered Pins 1 and 5 of the TL072 directly above the unicorn figure.
>
> Could this have caused damage to other parts of the circuit ?
>
>
> [Non-text portions of this message have been removed]
>