GGG Neutron build help :( on a breadboard - 7660S wiring and grounding?

[great_sushi]

Hi All,

Thanks for taking the time to read through this. I really appreciate it.
So yesterday I decided to build the neutron on a breadboard off general guitar gadgets website.

Project file: http://www.generalguitargadgets.com/effects-projects/filters-envelope/neutron/

Schematic: http://www.generalguitargadgets.com/pdf/ggg_neutron_sc.pdf

I'm fairly certain the layout and parts I've used are correct. There's probably one thing I've done wrong but I'm not sure.

I've used the 7660S single battery supply mod. And I'm getting 18V between pin 5 and 8. and -9 and +9 relative to ground from pin 5 and 8. I've checked the voltage at every IC and they are correct with the correct polarity.

At the input I have a stereo jack, with the ring going to the 4k7 ohm resistor to the base of transistor. And the tip is connected to the gain pot.
The two guitar lead (input-output) signal grounds are connected together with a single line coming off them going to my ground rail on the breadboard. Where everything connected to ground is connected there.

My issue is where to put the negative battery lead? Will that also go to my ground rail? Or is that solely supposed to be connected to the 7660? If so, which pin?
Because at my for eg low pass filter output I get more audio coming through without the battery connected. Which suggests something is wrong.

I am getting the classic 7660 whine but I'm not concerned about that until I can actually get the effect working and I can try modifying the 7660 circuit.

Can anyone help me diagnose where I'm going wrong? Even if it's a case of going through every pin and reporting back the voltage relative to ground at each pin etc.


Also, I have been probing the circuit with the output to the amp lead. The volume reduces a lot at the first op amp.
And, I haven't been using the NP cap at the output with 560ohm resistor since I've been getting no output. 15uF non polar cap. Can I use ceramic or shall I wire two 30uF electrolytic caps together to make a single NP 15uF cap?

Cheers

[bluebunny]

Welcome.

All the ground symbols in the schematic are the same place, including the negative lead from the battery: connect them all together somewhere convenient, like the ground lug on one of the jacks.  To avoid the whine, you need to short pins 1 and 18 of the 7660S.

[great_sushi]

Thanks for your reply. I did that the first time but got no signal through. Which made me think something was wrong with the grounding.

I was looking at the wiring diagram on the first link I sent inside project pdf and that has:

Battery positive to Emitter of Q1
Battery negative to the negative side of C15 to the Collector of Q1
Input stereo lug - R20 (4k7ohm) to Base

Then tip of the stereo input to the gain pot.
Is that correct?

I'm not sure if thats including the 7660.

http://www.madbeanpedals.com/projects/Nautilus/Nautilus.pdf
This is a similar schematic

http://www.madbeanpedals.com/projects/NaughtyFish/NaughtyFish2015.pdf
This is probably the closest match to reference to.

[great_sushi]

So I think I've sorted the grounding.

But the LED that drives the filter is constantly on and I hear a tiny amount of audio passing through that doesn't seem to be affected by the filter and a very loud whine.
I'm using 7660S and it doesn't help to connect pins 1 and 8

Would it be useful if I measure the voltage on every pin?

[great_sushi]

Cool.. thanks for the reply

I'll try disconnecting R4 and C4 and ensure the gain stage is functional.