About to embark on VCO-1 and had a few questions...

[jimmyschaus]

Hi all,

I'm currently working on a modular. Up to this point I've been using pre-made modules and kits from PAiA, and I'd like to start constructing stuff more "from scratch" for the sake of both saving money and gaining experience in true diy-ness. I'm in need of another VCO and Thomas' "VCO-1" seems great.

First question (which is sort of a general one and maybe could be asked in a different area of the board, but whatever here it goes): I was planning on putting in the parts in accordance to the parts layout on a perf board and then sketching the current flow on the other side with a pen equipped with conductive ink. Is this a bad idea? It was suggested to me a couple of years ago by a professor and I am attracted to not having to design something on a computer and send it off to get printed, or having to use nasty etchant stuff myself. But the documentation on these pens describes them as good for making corrections, and I can't really find any evidence of people drawing out whole circuits with them, so it makes me think it's a bad idea. Your input on this is appreciated.

Second, much more specific to the VCO-1 circuit, deals with the power connections. I have a 15V blacet power source which takes those four pin thingies. All of the modules I've used so far have the power connections lined up in a row (+15, two ground connections and -15), ready to connect with those nifty snappy things. Looking at the parts placement I notice what appears to be two ground connections, two +15 connections and two -15 connections. How would this translate to a 4 pin connector to the blacet power source?

Sorry if this is too rudimentary. Also be honest and let me know if it sounds like I should perhaps stick to kits a while longer while I learn more about electronics, as I feel like I am taking a plunge here into a more esoteric way of building stuff (which I think is a good thing, but maybe I'm not ready, I dunno).

thanks!
Jimmy

[andrewF]

Hi
don't use a conductive pen, nor do you need to design/etch a pcb, use a veroboard/protoboard;
like these http://www.futurlec.com.au/ProtoBoards.jsp
the 777 is big enough
much cheaper and much more reliable.

all +15V just go to the +15V on your connector, likewise for -15V, 0V is the same as Gnd and although there are two pins for these on the connector they are the same (connected).

Usually a VCO is not the easiest module to start DIYing, but this one is pretty straightforward. I have built two on protoboard and found them pretty easy and excellent to use.
Do not expect your circuit to work first time, if it does
but don't be disheartened. Troubleshooting is a part of building and it gives you a chance to learn more about the circuit in question.

i'm assuming you mean this circuit
http://mypeoplepc.com/members/scottnoanh/birthofasynth/id33.html
which means you will need a CA3080 or LM3080 (same chip different company). these are getting a bit hard to find, still on ebay tho.

give it a try, if it doesn't work after a decent attempt, put it aside and try something easier. You can always come back to it and finish it when you are ready.

have fun!

[creekree]

i built the VCO-1 as well and i like it. i have not used a tempco as i have yet to find a good source for those in germany.
i etched a circuit board myself, but i'd like to support andrewF's suggestion to use a veroboard, BUT personally i'd prefer to use pad-per-hole boards.
the components leads can be bend underneath to form traces, and if they're not long enough you can use solder blobs to connect the copper pads. also dont be afraid to use the occasional jumper wire.
following the PCB layout from Scotts site should get you far... (using the prototyping board andrewF suggested is not a bad idea at all, but you'll have to come up with your own component placement)

oh, regarding the CA3080: you might want to use a LM13700, its two 3080s in one package. this IC is more common (and, oddly enough, cheaper) and you could build two VCO-1 with it

as always: take your time, think about what you're doing, and take notes. especially those will help you when it comes to troubleshooting.