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How does the I/O fit in?
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Please be positive and constructive with your questions and comments.

Re: Testing VCO with soundcard scope. Doesnt look the same.

by Pish on Thu Apr 25, 2013 1:59 pm

VCF.


I'm getting nothing with the cuttoff and res down but I'm getting these with the resonance up.

Image

Image

BUT because I broke the probe tip im using a cheap BNC to Croc clips, which have some interference. Is this a problem? Or carry on?
Pish
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

by MMM on Thu Apr 25, 2013 2:40 pm

Measure again with Cutoff max and Resonance zero.

My guess is that you'll get some result then.
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Re: Testing VCO with soundcard scope. Doesnt look the same.

by Pish on Thu Apr 25, 2013 2:44 pm

Cheers for the quick reply.
Im finding building easy but my test skills are useless!
Pish
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

by Pish on Fri Apr 26, 2013 4:52 am

Cutoff 100%
Nothing, but like I said its moving a bit but I think its interference, but I do get a wave for that switches when I get to about 30% Res.

Although I must say I have done a couple of bad solders on the big holes for the pots on the Res, which I will fix later today.

I replaced the TM3 in the kit with this, as I damaged it when I put it in the wrong place doing the power.
http://cpc.farnell.com/bourns/3362p-1-5 ... is%20Range

With headphones I get sound if I have resonance to about 10%, before that electrival noise, the switch does change it frome square to saw too. Carry on?
Pish
 
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Re: Checking The VCF

by MMM on Fri Apr 26, 2013 10:21 am

Where exactly do you attach the probe? I suggest measuring at the "-" side of C14.
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Re: Checking The VCF

by Pish on Tue Apr 30, 2013 5:42 am

Going to wait for my replacement probe tips to come. I was checking on the VR4 pin furthest from C13.

Checked that the Transistors and Capacitors are the correct ones and that they are in the right way.
Going to check all the resistor values now.
Pish
 
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Re: Checking The VCF

by Pish on Tue Apr 30, 2013 12:06 pm

Everything checks out fine except
220K...R63 (seems to measure 7k)

10k...R116/112/65/64 (seem to measure 7k :/)

I need to check the colour codes on these, then maybe swap them out.
Pish
 
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Re: Checking The VCF

by Pish on Tue Apr 30, 2013 12:55 pm

Colour codes are right.
Pish
 
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Re: Checking The VCF

by Pish on Tue Apr 30, 2013 1:10 pm

Although... Ive used AP's at Q8/9/10 and a 945P at Q11. Thet are the same pinout right?
Pish
 
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Re: Checking The VCF

by MMM on Tue Apr 30, 2013 2:43 pm

I guess at this point it would be easiest to wait for your replacement probe and then walk through the filter.

There are a number of possible faults. Could be that the cutoff part doesn't work; could be that somehow the oscillator signal doesn't reach the filter ladder... We'll see.
MMM
 
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Re: Checking The VCF

by Pish on Tue Apr 30, 2013 4:56 pm

Hopefully it will be here tomorrow.
I have the Eagle file. Do I just check the voltages are the same as the file at each point?
Pish
 
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Re: Checking The VCF

by MMM on Tue Apr 30, 2013 5:10 pm

No, the voltages from that file are essentially the DC voltages. This is helpful to a certain degree but not always. What we are interested in is the audio signal which is an AC voltage sometimes traveling on a large DC offset. For example, in the filter ladder we have a DC bias of about 10V; on top of which rides the audio signal with about 100mV peak-to-peak. This also means we need to use the scope in AC coupled mode sometimes.
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Re: Checking The VCF

by mavzz on Sun May 26, 2013 5:19 am

I have the same problem with the Willzyx kit after building the VCF: when the Resonance is set to min, there is no detectable wave, regardless of the Cutoff level. When the Resonance and Cutoff are set to max, then the wave looks like this:

Image

Pish: did you manage to figure out what was wrong?

Any suggestions?
mavzz
 
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Re: Checking The VCF

by MMM on Wed May 29, 2013 7:04 pm

Pish: If you're still reading here - you need to measure at the VR4 pin closest to C13, not the other one. Your filter is probably fine.
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Re: Checking The VCF

by Pish on Fri Jun 21, 2013 4:12 am

Cheers people. I havent got back to it yet been busy. Hopefully on it when I get back from Glastonbury next week. I just want to finish and have a TB303 vs TBX303 vs x0x battle with my friends!!!
Pish
 
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Please be positive and constructive with your questions and comments.