Problems with my Steiner VCF (CA3096)

Aottens · Joined: Mar 14, 2010 Posts: 33 Location: The Netherlands

Hello, I've built the filter, but there are some problems with it. And I don't really know how to solve them.

I've checked the connections and the parts, and everything seems fine.

1. De cutoff frequency potentiometer is not really working. It doesn't seem to work on either position (LP HP BP AP)

2. The output level of HP and BP are really low

3. If I adjust the control level (cutoff freq), nothing happens.

4. When I turn the resonance potentiometer, the only thing I hear are some crackling sounds. Do I need a new potentiometer for this? If the answer is yes, please give me a link with the right one I can buy!

What can I check, and are there some measurements I can perform?

Thanks for the help!

kkissinger · Posted: Mon Feb 13, 2012 2:23 pm Post subject:

I've built many Yusynth modules, including the Steiner VCF and every problem I had was due to cold solder joints.

For starters, check every connection for continuity with a volt-ohm meter. I know this sounds tedious, but in the long run it is the quickest way to find problems. Pay special attention to Diodes -- cold or weak solder joints are almost impossible to see.

You can check this with your continuity tester by placing one test probe on a trace and the other on the leads to the parts -- in other words, one probe on the trace side of the board and the other on the corresponding leads. (of course, do this when your module is disconnected from the power supply).

AlasdairMoons · Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium

kkissinger · Posted: Mon Feb 13, 2012 4:33 pm Post subject:

Fortunately the Steiner VCF has few parts and the PCB is not too dense. Shouldn't take more than 30 minutes to check everything.

Also, when nothing seems to work -- the first thing I check is the power supply. Make sure that the +, -, and GND connections are secure (and that the polarity is correct). Check continuity along the traces -- a microscopic break in a trace is all it takes to make an open circuit. Check the polarity on the parts.

In my case, I etched my own PCBs and, since the traces are not tinned, it is a little harder to solder than commercially-made PCBs that have nice tinned connections.

Most importantly, don't give up. Just take a deep breath, check everything, and keep looking until you find something (a broken trace, cold solder joint, or reverse polarity).

The Yusynth Steiner VCF is a wonderful filter -- well worth the effort.

Aottens · Joined: Mar 14, 2010 Posts: 33 Location: The Netherlands

Thanks for the reply's guys! Much appreciated! I will check the solder joints when I get home from work today. Also I'm going to check the polarities.

I will come back at you if it works Wink

and also if it doesn't.