Sunface Clone Oscillation when Fuzz is at 100%

[jbar93]

Hi everyone, I tried searching for an answer, but could not find a clear one on the topic

I have built a Sunface clone based of this layout: http://effectslayouts.blogspot.com/2015/04/analogman-sunface.html

I built the Ground Negative version and used BC109's instead of BC108's

It sounds great, but when the fuzz is turned all the way to 100% there is a loud oscillation sound.

Rolling off the guitars tone knob removes the oscillation.

Playing with the q2 collector bias knob (Sundial) lessens the oscillation somewhat but never removes it.

Has anyone able to help me resolve this issue, preferably without compromising gain etc?

Transistor values are as follows;
Q1 e0V, b0.57V c1.19V
Q2 e0.61V b1.20 c4.45V(when sundial at 0%) and 7.49V(when sundial is at 100%)

Cheers for any help given

[thermionix]

squeal or motorboat?

[jbar93]

It's like a high pitched whine

[thermionix]

Battery or external power supply?

[jbar93]

Battery only

[thermionix]

Okay, you've got an oscillation.  Could be layout related.  Move wires around and see if that has any effect on the squeal, changes the pitch or anything.  It's possible lower gain transistors will be required.

[jbar93]

When I touch the connections of the input it produces a loud buzz, also when the fuzz wires and input wires touch it modulates the squeal somewhat. Not sure if this helps

[thermionix]

Not sure if this helps

It probably does.  When dealing with high-gain circuits, keep wires as short as possible, and seperate input and output wires best you can.

[antonis]

Try placing 47-100pF caps between Collector & Base of transistors..
(you may start with 100pF caps on both BC's and lowering their values for an acceptable overal gain level with no squealing - you even might need only one NFB cap..)

[jbar93]

Attached is an image of the inside as it is currently, Thinking I might reroute the wiring so clean it up a bit to see if that helps, otherwise will look at capping the transistors. Cheers for your guys help.

For reference;
White - input
Blue - output/volume
Green - ground
Black - Fuzz
Orange - Sundial
Battery terminals are red- positive, black - negative

[Rob Strand]

The wiring looks like it's asking for trouble:
- You've got too many wires going to the output (orange ones) going close to the input.
   Especially that orange wire which starts on the right of the board and loops back
  over to the bottom left and under the input socket.   That's an output wire
   and it's wrapped all over input wires.
   Make all your orange wires short.
   Route them so they are all on the right hand side, with all the output stuff.
- The white wire connecting to the IN point on the PCB is running close to the output socket.
   Push it over to the left.

Some key things are:
- keep input stuff away from output stuff (and visa versa)
- keep signal wires (or wires that connect to signal wires) short.

[patrick398]

That output jack is guna need grounding no? Am i missing something?

[jbar93]

Thanks for the advice, I will definitely change the wiring and see what results that produces. Wiring Interference didn't occur to me when i wired this.

Also, the shields of both inputs is grounded as they have a connection to the pedal enclosure.

[duck_arse]

many a person has thought they had ground continuity through the pedal enclosure, only to find adding "the wire" cures problems like rattles and humms.

[italianguy63]

many a person has thought they had ground continuity through the pedal enclosure, only to find adding "the wire" cures problems like rattles and humms.

+1

I always wire the ground lugs just out of general principle.

[jbar93]

I checked the continuity between shields while I was assembling the pedal and it existed so I didn't bother with a wire. Might add it and see if it cures my problems

[patrick398]

May not cure your problems but i think it's best practice to ground your jacks just in case one manages to wiggle it's way a little free from the enclosure.

And we all know the only time when that is going to happen is at the worst possible time it could happen

[fishdog]

Connect a 100 ohm resistor to lug 3 of your fuzz pot or whatever lug the 100k resistor goes into and I bet it will quit 👌🏼

[jbar93]

I rewired the orange wires so they were shorter and away from the input wires. Also moved the white input wire away from the output side. The oscillation is fixed so thanks to all that help.

I noticed then as well that when I turn up the volume knob to full i get oscillation. Probably will have to shorten and rewire the blue wires to fix this. Not sure if this was always happening or I just created this problem. Don't think I'd turned the volume till full for now.

I cant see myself turning the volume to full, so for now it's not an issue.

Thanks to all that helped solve my problem. Think I have learnt a lesson on the importance of proper wiring in a pedal

[Rob Strand]

I noticed then as well that when I turn up the volume knob to full i get oscillation.

Try putting a small cap, like 47pF, from the PCB input to ground.

(Fishdog's suggestion might also work.  If 100R doesn't work try 1k.)