[sdiy] 4069 CMOS VCO Trouble-Shooting

[Scott Gravenhorst]

"Michael David Brown" <1browm13 at solent.ac.uk> wrote:
>I am trying to breadboard Rene Schmitz 4069 CMOS VCO
>http://www.uni-bonn.de/~uzs159/
>
>I had this circuit generating the sawtooth output with freq' 
>controlled by 22k Lin pot, 

This should work as a test, but note that in practice, if you want this to scale
correctly, the 22K pot should be replaced with a voltage controlled current source.

As far as layout goes, I did discover a sensitivity to which inverters were used
for what purpose - and this was verified by René.  Note that it may affect only one
manufacturer's die.  My problem was not the VCO itself, that always worked, rather
I had problems with the PWM portion (noise burst instead of a rectangular edge). 
After using the pin details I got from René, it worked perfectly.  You can see my
pin details here:

http://home1.gte.net/res0658s/fatman/VCO_pwm_tri_suboctave.html

Other than that, it ought to work.

>then the waveform dropped out and i 
>cannot trace it. I've replaced; transistors, tested the IC, 
>checked earth checked connection etc. The Circuit demonstrates 
>the waveform when the power is reconnected but only for a split 
>second. there is a signal source that can be acted upon by the 
>potentiometer but this is not the waveform. Does anyone know of a 
>solution? 
>
>Does anyone have a good breadboard and vari-board layout for this VCO?
>Does anyone have a similar yet better design?
>
>Thanks,
>Michael Brown
>
>

---------------------------------------------------------
- Where merit is not rewarded, excellence fades.
- Hydrogen is pointless without solar.
- What good are laws that only lawyers understand?
- The media's credibility should always be questioned.
- The only good terrorist is a dead terrorist.
- Governments do nothing well, save collect taxes.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- Autodidactic Master of Arcane and Hidden Knowledge.