# Tone control in Little Green Scream Machine



## Olivier7960 (Nov 14, 2021)

Hello 
I just built the Little Green Scream Machine and I love it. I don’t know if you guys have the same issue but the Tone control has very little effect on the sound. Did I do something wrong ? Is there a value that I can change somewhere to have more impact on the sound ? 
Thank you for your replies


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> Hello
> I just built the Little Green Scream Machine and I love it. I don’t know if you guys have the same issue but the Tone control has very little effect on the sound. Did I do something wrong ? Is there a value that I can change somewhere to have more impact on the sound ?
> Thank you for your replies


Did you use R7 - 220 ohm resistor, not 220K
220 ohm - Red, Red, Black, Black Brown.


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## Olivier7960 (Nov 14, 2021)

Yea it is a 220 ohms metal film resistor, 0,25 watts …. Red Red Black Black Brown


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## JamieJ (Nov 14, 2021)

Can you post pictures of the component side and solder side of the board?


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> Yea it is a 220 ohms metal film resistor, 0,25 watts …. Red Red Black Black Brown


PICTURES!
I'm still thinking Resistors, 10K & 1K!


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## Olivier7960 (Nov 14, 2021)

Ok I will double check the resistors with the Color codes … in the meantime here is a picture of the build


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## Olivier7960 (Nov 14, 2021)

Mmm I double checked all the values and they are ok


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## Olivier7960 (Nov 14, 2021)

I will unscrew everything and post a picture of the underside in a moment


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> I will unscrew everything and post a picture of the underside in a moment


Did you use a Dust Cap on the Tone pot.
It needs to be properly insulated or it will short on the Solder tits!


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## Olivier7960 (Nov 14, 2021)

I am still waiting for the dust caps … in the meantime I put a piece of cardboard between the pot and the pcb


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> I am still waiting for the dust caps … in the meantime I put a piece of cardboard between the pot and the pcb


Has this solved your issue coz the rest of the Build looks very neat!
I have to ask, Did you use a W20K or B20K?


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## Olivier7960 (Nov 14, 2021)

Unfortunately no ! The piece of cardboard was already there when I first noticed the problem … I don’t know what to do … it’s like the pot has no effect at all … could it be faulty ? If it were I guess the circuit wouldn’t be working … but I have a good sound with little noise … I can play with drive and volume but the tone …. Nothing


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> Unfortunately no ! The piece of cardboard was already there when I first noticed the problem … I don’t know what to do … it’s like the pot has no effect at all … could it be faulty ? If it were I guess the circuit wouldn’t be working … but I have a good sound with little noise … I can play with drive and volume but the tone …. Nothing


Can you test for Continuity on matching circles .
You can also set DMM for resistance & Test if it vary's between Leg 2 & 3, Leg 2 & 1:


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## Olivier7960 (Nov 14, 2021)

By the way thank you for your help….
Resistance varies between the legs …. 
There is good continuity between the points you circled …..


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> By the way thank you for your help….
> Resistance varies between the legs ….
> There is good continuity between the points you circled …..


Can you test for Continuity from opposite blue 220nF pad to top of 220r resistor?
You can see the trace in the PCB above!
Did you use a B20K for Tone pot?
Did you measure 220nF Cap prior to install?


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## Olivier7960 (Nov 14, 2021)

Yes there is continuity on the pcb trace you mentioned. I just measured the 220 nf cap and it reads 216 nf…. I used a b20k pot for the tone and the measurements I made confirm this


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## Dan0h (Nov 14, 2021)

I just finished this build and used the specified “w20k” pot and it has very noticeable tone shaping as you twist through. I find it hard to imagine a B20k would not work but maybe that’s why they suggest using the W20k. Post a pic of the bottom of your board. My guess is you have some cold joints.


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> Yes there is continuity on the pcb trace you mentioned. I just measured the 220 nf cap and it reads 216 nf…. I used a b20k pot for the tone and the measurements I made confirm this


In simple terms in this circuit:
a B20K will only work in the first 1/3 of the pot rotation then basically nothing thereafter, you should hear something.
a W20 has an even sweep over the rotation of the pot that's why it is recommended!
a  A20k bunches it all up in the last 1/2 of the rotation.

You may have a cold joint but the pedal is functioning??????


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## Popnfreshbass (Nov 14, 2021)

Needs to be w20k from what Ive read. Otherwise you get the problem you’re having.


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## Olivier7960 (Nov 14, 2021)

I just took the multimeter to measure all the resistors … even if the Color codes are correct some don’t read the appropriate values … two 10k read 5k and two 510k read 400k …. Could it be the problem ?


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## Olivier7960 (Nov 14, 2021)

I ordered a w20k pot … what is the code on the pot ? Mine reads b20k


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## music6000 (Nov 14, 2021)

Olivier7960 said:


> I ordered a w20k pot … what is the code on the pot ? Mine reads b20k


You can't measure resistors accurately once installed, If they are parallel or in series with other resistors they give the wrong readings!
It should read *W20K.*
It is readily available because of the Tube Screamer pedal.


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## Olivier7960 (Nov 14, 2021)

I. Checked my order and it was for a w20k potentiometer. On the one I received it’s written b20k …. So it’s definitely the wrong one ?


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## Dan0h (Nov 14, 2021)

Olivier7960 said:


> I. Checked my order and it was for a w20k potentiometer. On the one I received it’s written b20k …. So it’s definitely the wrong one ?


Yes. You received the wrong pot. Re-order the W20k and you should be good if that is the only issue.


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## Olivier7960 (Nov 14, 2021)

Ok I will do that. Thank you !


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## Olivier7960 (Nov 27, 2021)

Hello
Well I installed the w20k potentiometer and it makes no difference regarding my prior issue. As I sweep it I cannot hear any effect on the sound. Everything else works fine and sounds good …. Maybe I damaged a component while soldering ? But in that case it wouldn’t be working at all ? I checked my resistor values and they are right … maybe I should just try to build it again …


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## Chuck D. Bones (Nov 28, 2021)

Perform a thorough visual inspection of all components and solder joints with good light and magnification.  95% of all build problems are due to workmanship.  Most of the solder joints look good from the top, but quite a few have holes that are not filled with solder.  Inspect first, then reflow as required.  No shot-gunning please.

A B-taper pot will definitely vary the tone, it would just be much more sensitive at the ends of the travel.

BTW, we have a Troubleshoot forum specifically for troubleshooting.


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## Bricksnbeatles (Nov 28, 2021)

The overall scope of variation in a B20K is identical to that of a W20K. The 0%, 50%, and 100% positions will be identical, and anything in between will be equally attainable with either pot taper, just in slightly different positions. If you’re not getting an appreciable change in tone from fully CCW to fully CW, the pot taper is 100% not the issue. If the problem is just that the difference between 12:00 and 1:00 on the knob isn’t as noticeable as you’d like, then it would be an issue of the taper.

Plenty of TS clones use a B taper and it’s totally fine— just makes for some slightly different knob positions for specific settings, but any setting that would normally be possible is still achievable. 

You said that you checked your resistor values— check that everything is soldered properly, and check your capacitor values.


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## Olivier7960 (Nov 29, 2021)

Hello
Thank you all for your input. Thank you Chuck D Bones for your comment I realized that most of my solder joints were not done properly. I didn’t think that the solder had to flow through the hole and cover both pads, I thought I needed to put on the down side only ( newbie !!!!!) with a little fiddling I found a technique to do it properly. But I couldn’t fix all of them so I’ll have to start over … at least I learned something ! Will be working on the promethium distortion soon it looks cool !


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## Dan0h (Nov 29, 2021)

Olivier7960 said:


> Hello
> Thank you all for your input. Thank you Chuck D Bones for your comment I realized that most of my solder joints were not done properly. I didn’t think that the solder had to flow through the hole and cover both pads, I thought I needed to put on the down side only ( newbie !!!!!) with a little fiddling I found a technique to do it properly. But I couldn’t fix all of them so I’ll have to start over … at least I learned something ! Will be working on the promethium distortion soon it looks cool !


On a side note. I recently built the hoof pedal and it didn’t work. Very frustrating but after inspecting the back of the board under magnification and light I found a very tiny micro bridge of solider connecting a resistor and capacitor that were next to each other. I could not see this without magnification but that tiny little issue caused my pedal not to function. This was build #41. So don’t be discouraged at all it happens to all of us, just make sure when trouble shooting to really inspect everything up close. Good luck.


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## giovanni (Nov 29, 2021)

Olivier7960 said:


> Hello
> Thank you all for your input. Thank you Chuck D Bones for your comment I realized that most of my solder joints were not done properly. I didn’t think that the solder had to flow through the hole and cover both pads, I thought I needed to put on the down side only ( newbie !!!!!) with a little fiddling I found a technique to do it properly. But I couldn’t fix all of them so I’ll have to start over … at least I learned something ! Will be working on the promethium distortion soon it looks cool !


I don’t think Chuck was implying that solder has to necessarily flow on both sides in order to have a good joint, but that it may be a sign of a cold joint or not enough solder on the other side. That’s what visual inspection is for. I would check the pads that don’t have solder in the back and make sure they look good in the front.


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## Chuck D. Bones (Nov 29, 2021)

If all you need is some solder touch-up, then don't give up on this board just yet.

The best time for inspection is during the build when you can see everything easily.  If you do that, you're much less likely to end up in troubleshooting mode.


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