which VCO schematic is right?

[Peter van Hamersveld]

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.