Has anybody got Volca Schematics?

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zodiak
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Has anybody got Volca Schematics?

Post by zodiak » Wed Nov 25, 2015 9:18 am

I am doing some mods on my volca bass, but I am working blind and could really use a schematic.
For example, the VCO outs, are they buffered? (probably not) Do they come via a resistor ? (possibly) Are they AC coupled? If not the output signal could be centered at 4.5V so plugging that into a DC coupled mixer could cause issues both ways.
I am going tohave to assume the worse case for all of these and feed the outs via an opamp with a capacitor in the output, which means I will need to make the expansion box on the back even bigger :-(

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jensu
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Post by jensu » Wed Nov 25, 2015 9:27 am

Somebody correct me if I'm wrong. But i'm pretty sure they don't exist in the wild, and that all mods that have happended until now has been based on poking around.

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tonymatte
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Post by tonymatte » Wed Nov 25, 2015 9:32 am

Yeah I think you're right jensu. I did some searching a few months ago with no luck.

Be sure to post here if you find anything!

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zodiak
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Post by zodiak » Thu Nov 26, 2015 9:29 am

Its not just me then.

I have managed to reverse engineer them for parts of other PCBs by photographing both sides, reversing one and then use photoshop to flick between layers, but these are a right pain.

Too many tracks under pots, PCB too dark to get a clear image, SMD devices that could be a cap or a resistor, unmarked ICs, so after an hour and getting nowhere I thought screw this and gave up. I don't mind when I am getting results but this wasnt going to yield anything I would have enough confidence in to do anything useful.

More than anything else I wanted key follow so that I could get more than an octave of deep down growl, with no high harmonics but I think I have that cracked after watching a youtube video. I didn't like his total solution but he gave me the idea of lifting the wiper on the Filter cutoff pot, and using the track left behind as a way into the summing point on the VCF CV in mixing circuit.

The only other things I really want are keyboard voltage out, and that has a pad, and trigger out, and that will take some detective work, starting around the envelope pots. That way I can use it to trigger my mini modular.

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Post by Jarno » Thu Nov 26, 2015 11:01 am

And, is it sure this is not a 4-layer PCB?

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zodiak
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Post by zodiak » Fri Dec 04, 2015 5:04 pm

I wouldn't be surprised, it is certainly has that feel about. I have worked out how to do the key follow, CV out and MIDI out are dead easy so if I can find a good tap off for trig out I will have done all the things I really wanted.
There are plenty of other outs which I could easily buffer, but that would just turn it into a limited modular, so I am going to accept it for what it is, a really nice little sequencer box and leave it at that.

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Post by DCW » Sat Jan 14, 2017 9:44 am

Hi, I need some help and I think you might be the right people to help me. A friend of mine used the wrong power supply for his Volca Keys and it stoped working. He sent it for repair and it "couldn't" be repaired. After that he gave it to me. I opened it and realized that who ever tried to repair it did a very bad job. I already posted on the Korg Volca Forum, but haven't got any replies.

I need to know the voltages from the Power Stage of the PCB. On the Diodes and on the voltage regulator. So that I can troubleshoot it, or so that I can build a replacement Power Stage for the circuit.

Here you can see the fotos of the parts for which I'd like to have the Voltage readings:

Original Post on Korg's Forum



Thank you very much in advance!

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zodiak
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Post by zodiak » Sun Jan 15, 2017 7:28 am

Sorry all my gear is in storage at the moment while we do work on the house. I will try to extract my Vkeys and take measurements, but it wont be for a few days sorry.

DCW
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Post by DCW » Sun Jan 15, 2017 4:51 pm

That would be great zodiak!
thanks a lot!

Diego.

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zodiak
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Post by zodiak » Mon Jan 16, 2017 2:06 pm

Sorry I could only get these readings, my probes are just too big to fit into those tiny gaps. And you are right those ICs should not be fused together. I dont understand how the right hand side of the diode can be 0V, I am pretty sure the probe was on but it was very tight.
Image
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DCW
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Post by DCW » Tue Jan 17, 2017 11:11 am

Thank you very much for the info Zodiak!

If you have time, you could try using a needle attached to the Probe of your multimeter to get to the pins of what I believe is the Voltage Regulator (the IC inside the yellow square).That's a nice little trick I learned from my father.
That would be veeeeery helpful :)

Just an idea: maybe the zero volt reading from the Diode would change if you press the power button while measuring.

Thanks again for your time!
Diego.

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zodiak
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Post by zodiak » Tue May 16, 2017 4:01 pm

Sorry I have not been around, we have been relocating and my stuff was packed up. Do you still need the readings? I should have my gear out again in a week or so and will have a go.

DCW
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Post by DCW » Sat Jun 03, 2017 8:36 am

Yes, I still need the readings :) !! Thank you!

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Post by puffinstuf87 » Thu Jun 22, 2017 12:47 pm

You mean like this?

Image

Gotcha. Also, full SVC manual here:Volca Bass service manual PDF

Enjoy!

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Post by DCW » Thu Jun 22, 2017 1:57 pm

THANK YOU!!!

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Post by old gregg » Sat Jun 24, 2017 4:12 pm

thanks !

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Post by Moos Gummi » Thu Aug 10, 2017 11:50 am

Hey Zodiak,

I see you got the filter to track the VCO.
Did you use the output of IC6 or did you find a better way?

Cheers,
Moos

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volca bass and keys

Post by noiseygear » Sun Sep 15, 2019 1:48 pm

zodiak

Hey hey zodiak!

i'm sure i've missed other threads of yours – and i understand that this is 4 years old – but i'm trying to mod my Volca bass and keys

i'd like something super simple, the ability to control the filter cutoff with a foot pedal

Did you ever find contacts for this, and do you think it would be as simple as connecting the Filter Cutoff pot to a jack socket?

thanks in advance!!

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zodiak
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Post by zodiak » Tue Sep 17, 2019 5:28 am

Wow long time ago, but I hardly use my Volcas so it is still on my list of jobs HOWEVER, somebody sent me a service manual with a complete schematic.

This is the VCF section so I would be tempted to just add another resistor to the point circled in red and feed the external signal through that.

Picture file

I don't want to post the whole service manual here, but a quick google search should find a complete copy, have fun.

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