Help with this noises on Tone Bender MK1 please!

[Rnk]

Hi!! Hello everyone, new member of the forum here, and new in the world of building pedals.

I am writting to you because I need some help desesperately with some noises on a Tone Bender MK1 build that are driving me crazy...

I have built the tagboardeffects layout of the Sola Sound Tone Bender MK1.

I'm using a set of NOS Allen Bradley Resistors and Philips Caps and Some Russian MP41A transistors.

I'm getting good fuzz tones but no matter what combination of transistors I have tried I'm always getting some noises when I touch the strings and even with the vibration of the guitar... here you can check the kind of noises:

https://www.youtube.com/shorts/D4d9eXYYVQ8

Is it a problem with the transistors? I have tried more than 20... Maybe I should check other type of transistors? Everything else seems to be okay...

Hope anyone can help me

Thank you very much!!!

[idy]

The transistors may be extremely noisy (leaky) and gating (misbiased).
have you tested them for gain and leakage?
Can you give us voltages for both transistors, all 3 pins?
Can you show us your build? Is it in a box?

many of us learned to measure gain and leakage here:http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current.

[Rob Strand]

Post a pic of your layout and enclosure.

How have you handled the positive ground in terms of wiring?

[JustinFun]

The transistors may be extremely noisy (leaky) and gating (misbiased).

With a mki and russian germs more likely that they're not leaky enough. Only time i've successfully used russian germs in a mki build was with NPNs which can be somewhat leaky. Russian PNPs are almost all zero leakage in my experience.

Good old AC128s are easier with this circuit.

[Rnk]

Post a pic of your layout and enclosure.

How have you handled the positive ground in terms of wiring?

Here go some pictures

The drawing schematic is the way I wired all the offboard, the lines crossed out are also wired

[Rnk]

The transistors may be extremely noisy (leaky) and gating (misbiased).
have you tested them for gain and leakage?
Can you give us voltages for both transistors, all 3 pins?
Can you show us your build? Is it in a box?

many of us learned to measure gain and leakage here:http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current.

I tested them with Tc 1 for gain and leak but didn't test the voltage...
They have actually little leak and gain.
They are all between 50-90 Hfe and 70-200uA although there is only one with 600uA!

Yeah...is in the box...

[Rnk]

The transistors may be extremely noisy (leaky) and gating (misbiased).

With a mki and russian germs more likely that they're not leaky enough. Only time i've successfully used russian germs in a mki build was with NPNs which can be somewhat leaky. Russian PNPs are almost all zero leakage in my experience.

Good old AC128s are easier with this circuit.

Yeah they are little leaky except for a couple of them that are around 200 and one that reads 630uA.

I have tried this ones in different positions and the noise is still there with the addition of more background hiss than with the ones with less leak....

[Rnk]

Sorry for my English guys...   I'm Spanish

[Rob Strand]

Check the metal pot chassis and the input sockets are making a good connection to the enclosure.

Also make sure you keep all the output wires away from input wires.  Especially the wires from the PCB to the volume pot.   Don't overlook the area around the switch.

Try adding a small capacitor from the input terminal to ground *on the PCB*.   Start with say 1nF to see if it has an effect on the problem.   Ideally you want to use the smallest value possible.

If that works then could leave it as a solution.

It is possible your transistors have low capacitance and that's causing the circuit to oscillate.  You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.

If you can change something which affects the noise then that would be a hint to what is causing the problem.

Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.

[Rnk]

Check the metal pot chassis and the input sockets are making a good connection to the enclosure.

Also make sure you keep all the output wires away from input wires.  Especially the wires from the PCB to the volume pot.  Don't overlook the area around the switch.

Try adding a small capacitor from the input terminal to ground *on the PCB*.  Start with say 1nF to see if it has an effect on the problem.  Ideally you want to use the smallest value possible.

If that works then could leave it as a solution.

It is possible your transistors have low capacitance and that's causing the circuit to oscillate.  You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.

If you can change something which affects the noise then that would be a hint to what is causing the problem.

Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.

Thank you very much for your answer! Going to get the caps and try your suggestions but sorry for my ingnorance the positions you mean are these for example?:

Also.. where can I put the cap across the collector and base of the transistors? In the same place where the legs go? In the transistor socket?

Sorry again for my ignorance....

[GibsonGM]

"Across the power rails" means from +9V to ground.  You could place it on the right side of the layout, top row to the one just below it which is connected to ground.  Place it just above the yellow 100n capacitors.

You can place a cap between the base and collector of the transistors anywhere, even below the board. Do not solder them TOO close to the transistors, the heat may destroy them (remove them from socket first!). Look closely at the layout - there is space to add them if you are careful.   

[Rnk]

Thanks everybody for the responses, really appreciated!!!

[Rnk]

Check the metal pot chassis and the input sockets are making a good connection to the enclosure.

Also make sure you keep all the output wires away from input wires.  Especially the wires from the PCB to the volume pot.   Don't overlook the area around the switch.

Try adding a small capacitor from the input terminal to ground *on the PCB*.   Start with say 1nF to see if it has an effect on the problem.   Ideally you want to use the smallest value possible.

If that works then could leave it as a solution.

It is possible your transistors have low capacitance and that's causing the circuit to oscillate.  You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.

If you can change something which affects the noise then that would be a hint to what is causing the problem.

Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.

PROBLEM SOLVED!!!    
 3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!

Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.

Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?

Thank you very much man!!

[Rob Strand]

PROBLEM SOLVED!!!    
 3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!

Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.

Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?

Thank you very much man!!

Cool.  3n is a large value.  If I saw that I'd be thinking something is wrong!

Not sure why it has a mid scoop sound.   You should be able to set the tone with the Attack pot.