NE566N Voltage Controlled Oscillator Problem

Thread Starter

Tony Elliott

Joined May 8, 2015
155
Hello All About Circuits,

I have made the attached schematic and have no sound of oscilloscope signal from the NE566N. I have tried three different chips from different distributors to test if I have a bad chip and still no luck. I have powered from a dual power supply at 15v with ground (seen in attached photo) as instructed on the schematic. The only thing I can think is the power supply is set up wrong? I have it set on automatic current and the schematic book says current drain is around 10mA. Can somebody please tell me what I am doing wrong???
IMG_1644.JPGIMG_1647.JPGIMG_1648.JPGFullSizeRender-4.jpg
 

Alec_t

Joined Sep 17, 2013
11,540
Well, you've shown the IC and description, but not the schematic of your actual circuit. Unfortunately, a view of the breadboard layout isn't very helpful.
 
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tindel

Joined Sep 16, 2012
726
Doesn't look like your op-amp is powered. or decoupled.

[edit] if you're using a 741 maybe you do have it powered
 
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tindel

Joined Sep 16, 2012
726
If I make a few assumptions of where your power rails are, It looks like the circuit is right... decouple the opamp... and also make sure that your scope is scaled properly. Other possibility is to make sure that the trim pot is linear.
 

sailorjoe

Joined Jun 4, 2013
363
Tony, when things aren't working it's time to forget about what you think you did, and figure out what you actually did. You powered the LM741 and the 566 from the same rails. Did you use a voltmeter or o'scope to prove that the hookup is correct? Did you measure right at the chip pins? Please don't guess....make a measurement.

Also, did you notice that the 566 has negative 15 Volts (-15V) connected to its pins, not +15V. That's unusual and something that could be missed.

And by the way, increasing the power voltages to +/-22V won't make it work if it doesn't work at +/-15V. 15 is more than enough.

Next step, measure the voltage coming out of the 741. Does it vary when you move the pot? How much does it change? Is it what you expect it to do?

If that works, put your scope on pin 7, the charging capacitor. Is there a signal there? It should look like a triangle wave.

Let us know how that goes, please.
 
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Thread Starter

Tony Elliott

Joined May 8, 2015
155
Tony, when things aren't working it's time to forget about what you think you did, and figure out what you actually did. You powered the LM741 and the 566 from the same rails. Did you use a voltmeter or o'scope to prove that the hookup is correct? Did you measure right at the chip pins? Please don't guess....make a measurement.

Also, did you notice that the 566 has negative 15 Volts (-15V) connected to its pins, not +15V. That's unusual and something that could be missed.

And by the way, increasing the power voltages to +/-22V won't make it work if it doesn't work at +/-15V. 15 is more than enough.

Next step, measure the voltage coming out of the 741. Does it vary when you move the pot? How much does it change? Is it what you expect it to do?

If that works, put your scope on pin 7, the charging capacitor. Is there a signal there? It should look like a triangle wave.

Let us know how that goes, please.
Thank you for your message, I'm going back to my studio this afternoon and try out your advice:) in the meantime I found this video
it's how to setup a -12 +12. I have setup a 0 to + voltage on my circuit not a - + supply.
 

atferrari

Joined Jan 6, 2004
4,071
Based on a personal experience well deep in my past, I would stop looking for the reason and take all. parts and wires out. Then I would rework the connections, inserting all ICs first, then connecting ALL commons, then ALL positive supply voltages, then ALL negatives and finally taking one IC to connect each pin in numerical sequence and then next IC, completing the last.

I use short wires so tracing actual connection is easier. The very first test is ALWAYS that all commons are common to the PSU. Then I check the other voltages and then signals.

If not the above, check that your common is everywhere where it should.
 

Thread Starter

Tony Elliott

Joined May 8, 2015
155
The circuit is now working I have been calibrating it today. Many thanks for all you advice. It was the power, I used my dual power supply, two in series to create a -15v, ground and +15v. :)

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