Post your Silicon Chip/Jaycar kit questions here!

Hi Mel,

OK, can you check your power input please? What voltage do you have going in from the socket?
Also please can you visually check that all components are in the right way round according to the layout.

Also please repeat your voltage readings this time putting the black lead of the meter on the metal tab of the regulator IC.

Regards

MarkT

MarkT,
Thanks again for your help. My power supply is a Radio Shack 9V 300mA unit and I read 9.15V at the tip. My readings across the ICs backwards are T2 case to IC2 pin 8: -2.82V. T2 case to IC3 pin 6: -2.86V, the negative of what I had previously read.
I can't see any places where I reversed the circuit, but I've taken pictures of the front and back of the board if you don't mind reviewing them:
front is http://www.halakahiki.com/theremin/IMG_2685.JPG
rear is
http://www.halakahiki.com/theremin/IMG_2687.JPG
As you'll be able to see in the pictures, there's a *slight* amount of browning on the board on a few of the pins of IC2, but there's no place that looks burned through or where I think I soldered across or cut circuits. Please let me know what you think.

Thank you very much,
Mel

Hey!
Here's another finlander with some trouble with the construction. Everything has so far gone smoothly, although my soldering experience is limited. What I didn't understand was the mounting of VR1. My potentiometer seems to be too small for the drawing on the pc board, and when I compare it to the picture, it just looks minor.
This must be a silly question, but any suggestions? Should I just wire it up somewhere else?

Hello again all.

Mel, are you sure the power is wired up the right way round? Either that or you have the leads on the meter swapped.

Jolea, yes, just wire it up, VR1 is the volume pot and pots come in lots of sizes.

Regards to all

MarkT

Hi people,

I was given one of these Theramins for xmas and have just assembled it.

This is my first ever kit although I have tinkered with a soldering iron for quite some time.

A few pics here:
http://www.wolispace.com/cgi-bin/a.pl?pid=&mode=cd&file=../html/documents/pictures/metal/theramin

My questions are about the electricity supply:

1) When they say 9VDC or 12VDC 300mA, what if I have a 10VDC 400mA? is the 9-12 a range?

2) And what about the 300mA - is 400mA ok.. how about 500mA or 100mA or 1.5A?

As you can see I have no knowledge of this and the last thing I want to do is blow it up as soon as I plug in the power.

Am I right in understanding amps as the current: how fast the electricity is flowing, and volts as the .. erm.. volts.. how many electrons are flowing in the current?

This potentially incorrect knowledge does not help me know if I will blow my Theramin with the wrong amps or volts tho.

Thanks

Wolis,
Thanks for sharing the pictures. Here are some answers about the power supply I got from the eBay seller when I bought my theremin kit.
Hope it helps,
Mel


"The theremin runs on 9V or 12V DC power. It has a 2.5mm socket so you can plug in an adaptor, or you can make up a wire and plug from radioshack so you can use a 9V battery instead.

If you wanted to make some modifications it wouldn't be hard to wire a battery in directly.

You can use ordinary ac/dc adaptors like they sell at radioshack or other electronics stores, the theremin can run on a 9V OR 12v adaptor. It needs a 2.5mm plug (tip positive) with a minimum of 300mA current. If you have an adaptor with higher than 300mA thats OK, the theremin will only draw what it needs. Radioshack have Catalog #: 273-027 that will definitely fit, but you can get similar adaptors at most stores."

Ah.. thanks MWaldorf, music to my ears:

"..with a minimum of 300mA current. If you have an adaptor with higher than 300mA thats OK, the theremin will only draw what it needs."

I will now wire-up 9VDC 400mA and let the world know what happens.

Im intrigued as to the concept of amps.. so there no upper limit?

So do you think a 9VDC 100,000 Giga-Amps would be ok?

The reason I ask about all of this is that I have a pile of old DC transformers from old bits of hardware.. and Id rather recycle than buy a new one.

Wolis,

I'm no electronics expert, I'm just relaying information passed on to me. Maybe someone with more knowledge can answer this one.

All the best,
Mel

Hi guys.. more fun with power supplies.

Im getting -5.45V on IC2 pin 8 and a transistor body.

The instructions say I should be getting between +5.6V and +5.8V so obviously I have done something wrong.

Unfortunately the instructions don't give any hint as to what might cause it not to be this magical voltage.

Checking other posts here I see reference to getting the power supply the wrong way round.. so I tried reversing it.. but get the exact same result!?!

Anyone have any ideas that can help me make sense of this?

Thanks.

I think the easiest way to sort this out would be to wire up a PP3 9V battery and use that for testing instead of a power supply.

Using a battery guarantees that the power going in is DC and that its the right way around.

If you use a battery clip as well it should be simple as the leads are coloured, Black for 0V (Ground or -) and Red for +.

When taking volatge measuements, you must make sure that the leads to the meter are in the right place too. Check the voltage from the battery to make sure the meter is working and reapeat the tests. Remember the black lead on the meter goes to - and the red goes to +.

When this is all done, replace the batery with a DC power supply, but using the battery for now will take out a couple of unknowns here.

Hope that helps.

Regards

Mark T