EM theremin, wrong voltages.

Transistor pinout also often depends on whether the pins are in line or if the center pin is staggered (usually a C / E swap).  You either need the datasheet, or you have to fully bias the transistor to really know, as biasing pairs of pins only gives you diode info.

No, everything is not good. All the transistor voltages are now perfect, however, when I measure across R24 (resistor that makes up part of the detector and goes to ground, I do not get 0.5 V. I get no voltage. if i measure the end of that resistor to neg terminal, i get about 9V. When i measured across all the resistors that run to ground, very few of them gave me any reading at all.

Thaddeus

I am learning right along with you Thaddeus, sometimes we need an engineer to look at a datasheet. I dissect the EWS but have never broke one. 

EM Schematic

I myself would think the input impedance into the LM13700 is high so a voltage reading across R24 or the mixer diode could be misleading. Be careful of Static issues.

Christopher

I see, so it isn't a problem that many of the resistors running to ground are getting no reading across them? do you then think it would be worth it for me to hook up the antenna circuits and the potentiometers, and see if it works?

I come from the school of try everything. I find the Moog oscillator different from what I have experimented with, they may not oscillate without the antennas attached. So hook them up!

Are you using a scope though what you are doing can be done with that meter I mentioned.

Christopher

I shall try hooking the antennas and the audio out up in a short while, all I have with me is a multimeter. (I'm abit under equipped as I'm merely trying to build a Theremin off my pocket money).

Thaddeus

Okay, i hooked both antenna up, and wired the sleeve of the 3.5mm jack to ground, and the tip to output point 10 on the VCA. all i get is a deep sort of static, doesn't change if i touch antennas etc. (pots still unconnected)

Thaddeus

You need to know if your oscillators are working. Does your meter have a frequency counter? That meter I recommend does. A primitive method is to place an analog AM radio near the osc and tune to around 572khz which is double the frequency. I like to tune to triple the freq at 858 khz. The osc will create a blank spot in the static on the AM dial.  Digital AM radios do not work for this test. Place a finger on the osc coil or transistor and you should hear a change in the radio, this is the most exciting moment in theremin building. If no change then you can only pray.

Christopher

Hi Christopher, sorry I've been away for so long, I figured out my power supply was incorrect, and built my own dual regulated one. Now that I have it all hooked up, I have the correct voltages between bases and emitters of the transistors in the pitch oscillators. However, when I read the AC Voltage across the variable inductor of the fixed pitch oscillator, it only read about 1VAC, much too low, it should be 10. I apso have another strange occurance in the volume oscillator. When I have the indcutor connected, the voltage between the base and emitter of the volume oscillators transistors read too low, about 4V. Whne I bypass the inductor in that circuit, I then get the correct 0.6 V.

The reading across the base to emitter of the transistors in the tuning circuits is also wrong, 0.6V instead of -2.6V.

Any ideas?

Thaddeus.