Jaycar Theramin Construction Problems....!

Posted: 1/10/2006 11:21:01 AM

From: London

Joined: 1/10/2006


I've just completed building my Theramin and am having trouble tuning it/setting it up. It says in the instructions that I need to use an oscilloscope but I don't have access to one, is it possible to tune without the scope.

Also, it's not making any sound at all, I've tweaked the coils slightly but have got nothing out of it, is this normal?

Posted: 1/10/2006 12:13:59 PM

From: London

Joined: 1/10/2006

I've been back to it and I don't think i have any power going to the IC1, I can see from the diagram that pin 14 is the ground but I can't see which pin is providing the power to the chip, can someone please let me know which pin it is.

You may have guessed that I'm pretty new to all this, the Theremin was a christmas present and I'm determined to make it work....

Posted: 1/11/2006 1:40:43 PM

Joined: 1/11/2006

Did you get it working? I am not sure as to the answer to your problem..sorry. However I just completed mine today and am in the process of tuning it. The pitch control is working it seems (although not a massive range) but the volume plate seems to also alter the pitch..Tell me if you get anywhere.
Posted: 1/11/2006 2:22:38 PM

From: London

Joined: 1/10/2006

Not a sausage. If I tinker with it I can pick up some long wave indian radio...

I think I've gone wrong with the soldering and I'm trying to fault find, I don't think there's any power going to IC1 so there's probably a problem in that part of the circuit, do you know what pin supplies the power to the chip?
Posted: 1/11/2006 9:08:21 PM

From: Kansas City, Mo.

Joined: 8/23/2005

Well, I looked the schematic and pulled up some specs on the chip however I am not sure which pin provides power.

Perhaps Lyndsaymon would be willing to get some voltage readings off of the various pins on IC1 and post them for you to use as a comparison.
Posted: 1/12/2006 9:37:53 AM

From: London

Joined: 1/10/2006

I've got the support number from the suppliers, I'll contact them, thanks for your help.
Posted: 2/1/2006 1:52:52 PM

From: Buenos Aires

Joined: 1/30/2006

The "power" to the MC1496 comes from the [Signal] and [Carrier] inputs. (pins 1,4,8,10) you'll see that these signals are the outputs of the oscillators.

Get any "MC1496 datasheet" and you will see that the 1496 is actually made of 8 transistors. Transistors have no "Power Pin".
Posted: 2/1/2006 5:07:44 PM

From: London

Joined: 1/10/2006

I've got her up and running and she's sounding sweet...


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