which VCO schematic is right?

[harry]

Hello "Killer Bees"

I suggest you stick with the first VCO you started, and stay away from
VCO2 and 3 until you get VCO 5 running. You need to gain the skill and
confidence that will come with sucess !!!

VCO 5 is pretty simple, VCO 2 or 3 are more challenging !!!  Ultimately, you will
probably like VCO3 better.  But it will be harder to find your errors with more parts
and much more complex design.

Trust me... I think you are close with VCO5...

H^) harry

Peter van Hamersveld wrote:

> We, the newbeez, have tried for a second time to cook a VCO. It didn't work of course (it only created a low background hum and lots of noise), but we made some progress, because we didn't cook a RSG (Random Smoke Generator) this time. We tried to build VCO 3a, from Tom's Cookbook (EFM). It's at:
>
> http://www.xavax.com/efm/cbook/vco3.html
>
> The fact that ours didn't work, can be caused by two reasons:
>
> 1) we suck at soldering parts together.
>
> 2) the schematic we used is wrong. (although we skipped the [KEY CV] part, the two [CV] parts and the [PWM] part (we did keep the [PULSE WIDTH] part.)
>
> I think 1 is possible, but 2 can be too, because if we take a look at the two schematics for VCO 3a, we locate differences between the one with the symbols (upper) and the lower one (with the 2D view of a possible print). For example:
>
> - the lower one has a 39K Ohm resistor from pin 6 on the IC to the ground, the upper has not.
> - the lower has a 120K Ohm resistor from pin 6 on the IC to the emitor of the PNP transistor, the upper has not.
> - i cannot locate the [RANGE] trimpot in the lower one
> - the 1K Ohm resistor at the base of the NPN transistor is going to COMMON on the upper drawing and to a big 10K trimpot on the lower.
> - the big 10K Ohm trimpot in the lower drawing at the center-bottom to IC pin 11, althoug this pin is completely unused in the upper
> - in general, the lower drawing is quited screwed up to us, but it does have some components the upper one does not have.
>
> Anyone having an idea what is right and what is wrong (please include or link a right diagram)
>
> thanks a lot once more from the famous newbeez Egbert und Peter aus den Niederlanden.