VCO and VCF trouble

Discontinued DIY products Anushri
#1

Hi,

i have some problems with my Anushri built from a complete kit by MI.
The main problem is the resonance control, even at the lowest setting, there
seems to be quite a lot of resonance. Furthermore, the pulsewidth isn’t at 50%
at the center position. I also experience tuning issues, but I guess I should
figure that out after getting the filter and the VCO working correctly.

I already resoldered all connections. The voltages I measured appear to be
correct.

Unfortunately I don’t have a better camera at hand right now, but I can try to
make better pictures of certain areas if needed.

Mainboard:
http://www.brechpunkt.de/paste/Ne0TLtGx.jpg
http://www.brechpunkt.de/paste/OhCS5MPp.jpg

Square derived from Sawtooth at 50% PW setting:
http://www.brechpunkt.de/paste/UCBl6J97.jpg

DC corrected Sawtooth:
http://www.brechpunkt.de/paste/ZeCYNc8B.jpg

Sawtooth Core:
http://www.brechpunkt.de/paste/6SDXZAk8.jpg

Square Wave with Filter fully opened and 0 Resonance:
http://www.brechpunkt.de/paste/p3WlskZu.jpg

Thanks for your help in advance :slight_smile:

#2

Are you sure you have used the right pot (100kA) for the resonance control?

#3

I am not 100% sure. Is it possible to measure the pot in circuit? (with the control board disconnected from the mainboard)

#4

Yes, this is possible (quite an exception!). You should measure 100k between both extremities.

#5

It is only 87k

#6

Hmmm must still be good…

Can you check the color codes of R51 / R52 / R53 / R54?

#7

The resistors are 470, 4.7k, 4.7k, 33k, so they should be correct.

What about the DC corrected sawtooth wave? Is it correct, as it appears somehow clipped?