Problem with NE566N VCO

Thread Starter

El Zu

Joined Jan 13, 2016
28
Hi!

I'm trying to make the Thomas Henry 566 VCO, the same from here, but have no luck with it. I use MFOS PSU with -15v, +15 and ground for power supply. I measure the voltage coming out of the 741 and 566 and it seems to be alright. It has non-changable strange oscillation from pin 4 and has no sound from pin 3 at all.

I have no oscilloscope, so I connect speakers to the pin 4 of the 566 to hear triangle wave. Is it correct to do like this?
If the problem is with bad 566 chip than how to figure it out?
 

GopherT

Joined Nov 23, 2012
8,012
The NE566 is not designed to drive such a low resistance load as a speaker. Check the DATASHEET, it should show maximum current output. Use your supply voltage and ohms law to calculate.

You could use an old-school crystal headphones as an improved option or, better, feed the output of Ne566 into a preamp of some sort (let us know what is available).
 

hp1729

Joined Nov 23, 2015
2,304
Hi!

I'm trying to make the Thomas Henry 566 VCO, the same from here, but have no luck with it. I use MFOS PSU with -15v, +15 and ground for power supply. I measure the voltage coming out of the 741 and 566 and it seems to be alright. It has non-changable strange oscillation from pin 4 and has no sound from pin 3 at all.

I have no oscilloscope, so I connect speakers to the pin 4 of the 566 to hear triangle wave. Is it correct to do like this?
If the problem is with bad 566 chip than how to figure it out?
I don't remember the 566 being rated to go to + and - 15 V. Maybe + and - 12 V.
 

Alec_t

Joined Sep 17, 2013
12,818
The failure to work is probably due to a poor contact somewhere on the breadboard, assuming everything is wired exactly as per the schematic.
 

Thread Starter

El Zu

Joined Jan 13, 2016
28
The failure to work is probably due to a poor contact somewhere on the breadboard, assuming everything is wired exactly as per the schematic.
I breadboarded it twice without any luck. Probably, it is bad chip. I will try to get a new one. Let u know.
 

hp1729

Joined Nov 23, 2015
2,304
I breadboarded it twice without any luck. Probably, it is bad chip. I will try to get a new one. Let u know.
Normally I would try to duplicate the circuit, but you choose a chip I don't have. I have worked with the 566 in the past, but they are long out of production it seems. Current price is about $10 and that is "used". Do you have a better source?
 

Thread Starter

El Zu

Joined Jan 13, 2016
28
Normally I would try to duplicate the circuit, but you choose a chip I don't have. I have worked with the 566 in the past, but they are long out of production it seems. Current price is about $10 and that is "used". Do you have a better source?
Yes, it is a discontinued chip. I will buy it on eBay this time.
 
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