VCO not working

tomdes · Joined: Dec 22, 2014 Posts: 2 Location: paris

Hi everyone,

I just finish the Yusynth VCO but it's not working.
I checked all the componements and cable, it seems everythings is ok.
Solder seems to be clean too.

The thing is when I do some mesure through my oscilloscope I have only DC voltage (straight line on the screen)

IC are ok too, I tried with others.

Here are the output :

Pulse : -4,50v
Sawtooth : -0,39v
Triangle : 1,35v
Sine : 1,86v

I'm quite new in electronics so if someone have an idea of what's wrong it's welcome.

I joined two picture of the pcb, both face.

Thanks

(there is a little error in one ground cable but I corrected it since)

http://imageshack.com/a/img910/1810/5U6oOh.jpg
http://imageshack.com/a/img912/4292/vWacsi.jpg

gdavis · Posted: Fri Dec 26, 2014 1:25 pm Post subject:

Any luck yet?

First check the basics - make sure all the IC's are getting proper power on their power pins.

If power is OK, we need to work on the saw tooth. The other 3 waveforms are all generated from the saw tooth, so you need to get that working first.

I would suggest looking at two things with the scope:
1. Check the saw output while adjust trimmer T3 (10k). If the DC moves up or down with as you adjust the trimmer, then U6a and U6d are OK.

2. Check pins 5 and 7 of U6. If you see a saw tooth there, then the core is working and the problem is after that.

tomdes · Joined: Dec 22, 2014 Posts: 2 Location: paris

Thanks for your reply.

Good to know how the thing work.

1. I checked the saw Output and when I move the T3 trimmer It's moving :

https://www.dropbox.com/s/15duvxh1mc7myv6/IMG_0576.mp4?dl=0

2. I also checked the pin 5 and 7 of U6 and I have a tiny sawtooth but oscilating at really High frequency :

https://www.dropbox.com/s/ctthavqs6cynwlt/IMG_0572.jpg?dl=0

IMG_0572.jpg

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