[sdiy] asm2 vco problems

[Magnus Danielson]

>
>
> anyone around here built the asm2? having some real trouble with the vco
> (vco 1)
>
> the schematics are here:
>
> http://www.elby-designs.com/asm-2/vco/vco-asm2-about.htm
>
>
> getting voltage on all the rails.
>
> oddly the outputs (square wave specifically) keeps putting out  a
> voltage...around 4 volts
>
> i resocketed the ic's.
> i resoldered the solder points.
>
> been testing for continuity and so far havent found any dead connections.
>
> i am stumped.
>
> next i am going to try replacing the caps (i hate pulling out caps :(
>
> any ideas? specific voltages i should be getting on specific pins?
> my project is going down in flames ;(

Check that pin 7 on the LM311 kicks, and at what rate. A particular issue
that have occured with the ASM-1 VCO (which is essentially what the ASM-2
VCO is), is that the reset time was not sufficient to empty the capacitor.
Increasing the capacitance on the reset circuit (such as fingering it!!!)
can make it operate properly.

I just added some more capacitance to ground, but it should really be
accross the LM311 if done properly.

I'd expect something like a few 100 kHz or so.

Cheers,
Magnus