Did you start from the beginning of the manual and work your way through on the breadboard?
Try getting the simple active low pass on pages 13 and 14 to work - that way you can start trouble shooting with a simple circuit and you can verify that you have things like the power hookups and op-amps working as expected. From there you can work forwards adding complexity step by step from a solid base. If one step works and the next doesn’t, then you’ll know exactly where to look.
Good luck.
in view of the welds, I would still advise you to pass a cutter blade or knife between the lines which must not have contact, in order to avoid any possible short circuit 
The problem is there are four op amps in the package, and the schematic doesn’t indicate which one was used in each position, so without a lot of tedious tracing of the breadboard and diagram (the former is hard, the latter is damn near impossible) it’s difficult to follow the signal paths and find the fault.
CAD is Computer Aided Design. As opposed to the hand drawn Klein schematics, which are very nice to look at, but lack pin numbers, which renders them less useful.
Thanks to all that replied with good recommendations! Electronics lab is all packed up now, because have an international journey tomorrow and that basically involved packing everything in the apartment into luggage. (digital nomad reasons basically)
I will likely get the meebilt translation of that into SMT made instead, because REALLY don’t want to hassle with that protoboard anymore. And yes, not having net labels or wires in a full schematic for the opamps was kinda the point where I was basically over attempting to make that function properly.
I don’t know who meebilt is, but a quick searched turned up a schematic from their github that you might want to refer to next time:
eurorack/diode-vcf/sch_diode_ladder-vcf_v2.pdf at main · tkilla64/eurorack (github.com)
Or - you could just grab the EDU DIY VCF kit from Erica Synths?
Cheers
Hi! I have an issue building this filter using the verified stripboard layout by Dud. The filter doesn’t work for most of the time but when feeding it a high pitched sound from my VCO while filter is completely open, you can hardly hear it. Do you know what can be the issue? I checked if the IC’s are powered correctly and checked for false connections between the copper strips.
Here are some photos:
There’s lots of good advice in this post:
In particular I would run a craft knife blade in between the tracks of your stripboard to ensure there aren’t any bridged connections.
Hi Moritz, hope you doing well.
I have a question regarding the diode ladder filter. I build this filter some time ago and im very happy with. I even did the improvements like switchable LP, BP, HP like you showed in later video’s but here’s my question.
My squarewave vco directly connected to my buffered mixer shows a well formed squarewave.
This one is when running through the filter with the resonance off and cutoff all the way up.
Why is my squarewave bend like some sort of Trapezoidal form? Does this look familiar to you? Hope you (or other members) can advise if this is normal behaviour.
This is on the LP output but should’nt matter because of the absence of the resonance and cutoff.
That’s what squares start to look like as you remove low frequencies. I assume you’re using this circuit since you mentioned having multiple outputs. There is a ≈5 Hz RC highpass on the input as well as a ≈1Hz one on the output of the circuit. Those should be low enough to not do much to your 200-ish Hz input signal but you could try replacing the 1u cap on the input with a larger one if it bothers you.
Hi Sandelinos, thanks for replying and yes, thats the circuit i used. Well, Moritz has 2 videos of this filter. One without all the knick knacks and the one with optimized parts of the first circuit and LP, BP and HP options.
I will investigate that capacitor you’re mentioning and let you know the results increasing or decreasing its value.
That’s not a problem with this VCF but the typical behaviour of AC coupled squared waves. See here.
Hi K. Ostas, thanks! Great info from @analogoutput now it makes sense to me why square waves getting malformed when going through a filter. 
A good one, great video’s too where he explains and builds modules. Great schematics too. I build the handclap module a while ago. So Meebilt is a great resource imho.
Mebilt is a great resource. I built their bass synth. It’s a great wee unit.
Thats a lot of pcb space wasted.
