Tone control in Little Green Scream Machine

[Olivier7960]

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

 

[music6000]

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.

 

[Olivier7960]

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 ?

 

[Dan0h]

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.

 

[Olivier7960]

Ok I will do that. Thank you !

 

[Olivier7960]

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 …

 

[Chuck D. Bones]

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.

 

[Bricksnbeatles]

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.

 

[Olivier7960]

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 !

 

[Dan0h]

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.

 

[giovanni]

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.

 

[Chuck D. Bones]

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.