Post your Silicon Chip/Jaycar kit questions here!

Posted: 6/20/2006 2:18:55 AM

From: Reus / Tarragona - SPAIN

Joined: 3/19/2006

Hello from Spain!
I bought a months ago a Jaycar and finally I've decided to adjust it (although I have to say I'm scaried about it). For example, I'm unable to find the "zero point" that gives a silence before playing the theremin.

Well, I've done the holes at the box in order to adjust it without open in, and I have those adjustments psoitions:
T2 (beside pitch antenna)

But I don't know the function of every adjustment, and which is the one I have to modify to find the "zero point".

Thanks in advance for your help, and please sorry my very bad English.
Regards from Spain.
Posted: 8/20/2006 4:54:45 AM

From: Australia

Joined: 1/21/2006

Hullo all, i built my jaycar kit a while ago and put it in a nice enclosure but now i feel like a change. I'm now building a theremin enclosure in the style of the Etherwave Standard theremin.

Now i was wondering if anyone has tried to modifiy the jaycar theremin to be able do pitch preview? I'm looking into it at the moment but my lack of indepth electrical skills are getting the better of me.

If anyone can help me on this quest i would gladly apreciate it.

Posted: 8/21/2006 1:48:36 AM

From: Undisclosed location without Dick Cheney

Joined: 2/21/2005

I just ordered a Jaycar kit, and I was thinking about trying to put a pitch preview into it, and I have a technician lined up to help me with it. (I've put together electronics kits before, but it has been a while and he'll be better than me at figuring out where to put in a pitch preview.) I'll be happy to post information about what I learn and how it goes, but I plan for it to be some months before I get around to working on the kit, so if you're in a rush don't wait for me.
Posted: 8/21/2006 3:29:58 AM

From: Australia

Joined: 1/21/2006

Great! I'm not in any rush really. The enclosure i'm making makes it easy to access the board and make modifications to is so anytime is good. I'll still keep working on the pitch preview but probably with no avail.

Posted: 9/7/2006 1:13:09 AM

From: Albany, Western Australia

Joined: 9/7/2006

I have just built the Silicon Chip theremin and an still battling with the delicate tuning and volume adjustments. After reading this thread I want to add Max's mods, and I found that the link to the online coil calculator does not work (can't find server).

Can anyone else access that link, or has it gone?

Cheers from Australia
Posted: 10/11/2006 12:14:00 PM

Joined: 10/11/2006

Hello every body. i recently bought this kit through thereminkits in Australia. i got the whole thing assembled last night and i was working on trying to tune it when all of the sudden the sound went dead and no matter how i adjust everything. it wont come back. all i can hear is a slow faint pulse similar to a heart beat. oh and when i checked the circuit board i noticed that the 7805 regulator was searing hot. is this the problem that people have been complaining about with this regulator. or is it somethin else, like me replacing that wierd headphone style adaptor jack with a standard stompbox style 9V jack.
Posted: 10/13/2006 11:38:15 AM

Joined: 10/11/2006

well i have replaced the regulator and it has stopped overheating. I also replaced q2 because it seems it is a common culprit in dead sc theremins. but it still is'nt working. all that ive accomplished is that it has stopped pulsing. oh and by the way i borrowed someones dmm and it seem that i cant get any voltage reading above 0.04 past the very begining of the circuit. is it possible that the overheated 7805 killed the two 2n4004 diodes beside it. any help greatly appreciated
Posted: 10/13/2006 11:00:30 PM

From: Kansas City, Mo.

Joined: 8/23/2005

Are you powering the theremin from a wall-wart style transformer? Make sure that the wall-wart is producing the correct voltage.

If the input power supply voltage is ok, and the output voltage is low, first check all the solder joints in the power supply part of the circuit. You may have cold joint or weak solder joint.

If that doesn't help, then look for a solder bridge or a short circuit. A direct short will pull the voltage down (and likely heat up, too).

See if any parts are heating up. Make sure that the diodes and other parts are installed with the correct polarity.

Anyway, start there. Good luck and keep us posted.

[i]-- Kevin[/i]
Posted: 10/14/2006 11:59:47 AM

Joined: 10/11/2006

yes i was using a wall-wart transformer when this happened. but i am unsure if it was giving the right amperage. it is called a one-spot and theyre made to power almost any type of 9v circuit as they can produce anywhere from 200ma to 1700ma depending on how much the circuit needs. however i am unsure if this ciruit has the ability to select how much amperage it needs and not just suck down the whole 1700ma. that and i dont know whether or not the one-spot is center tapped which the instructions say not to use.
Posted: 10/14/2006 12:46:03 PM

Joined: 10/11/2006

finally i have it working. it ended up being a simple solder bridge that looked like a circuit board connection now im on to tuning and eventually i will work on maxies mods. i have already made his linearizing coil and it does help somewhat. ill post som pics when all is said and done and thank you very much for the help kevin.

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