Debugging Living VCO

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

I just finished my Living VCO including all wiring, but:

- no short on the +/- or GND rails (measured)
- no saw or pulse on ANY of the 3 vco's (so. nothing literally)
- when switching between PULSE/SAW i notice a "click" and a audible hum (very low, but audible) which might come from the TL's.
- Wiring is Option 3

So my assumption: there's something with the CORE's as all three do not sound.

any idea where to look first ?

davebr · Joined: Jun 09, 2007 Posts: 181 Location: portland, or

I would start with minimum wiring. Power to one VCO only. No connections to CVS_?, Freq_?, LinDet?, PW_?, PWM? or Pulse?. Use the Freq trimmer to adjust. Check for low level signal on Saw. You only have the expo converter and the core to verify. If something is wrong here then start checking parts values. A scope on the waveform is always useful.

Dave

JoeMorris · Joined: Apr 26, 2009 Posts: 160 Location: Brighton

Just finished this, sounds great.
One question...
My LFO seems to run quite fast, with a minimum speed of around 20hz...
Is this right?
Joe

JoeMorris · Joined: Apr 26, 2009 Posts: 160 Location: Brighton

doh... that was supposed to be in variable slope filter....

bennethos · Joined: Apr 18, 2009 Posts: 31 Location: Belgium

Any news on you're debugging ? Smile

I'm also debugging... I have 2 out of 3 working like 75% ...

Check also the power on your ic's (pin layouts can be found by looking at the datasheet).

You definitely need a scope ! And like dave brown said minimum wiring. I only have a cable on the saw output (connected to my oscilloscope) & frequency with a 10 turn dial (don't short it ! ).