Angry Charles Bass Pot

[bobthebuilder]

Hey everyone - new pedal builder here.

I've recently built an angry charles and everything seems to work except the bass control. After 12 O'clock on the knob the volume cuts off suddenly. Before 12 O'clock the volume increases as the knob is turned CCW. I've given a preliminary look over all the solder joints, components, and correct orientation of the potentiometers, and nothing seems obviously out of order. Any thoughts on what could be causing this strange behavior?

 

[Flipguitarist]

The circuit should work correctly if C12 is turned around. The left side of C12 is biased at 0VDC and swings up to +/- 1.6V or so, clamped by D2 & D3. The right side of C12 is biased at Vref (+4.5VDC) and has the same AC swing as the left side. Once C12 has been exposed to reverse voltage, it has probably been permanently damaged and should not be reused. Install a new one.

*Update*
Removed and installed and reversed a new 2u2 on C12. It works as it should. You’re the man! Thanks a lot!

 

[Flipguitarist]

That's a good observation. Whether it's the issue or not, I don't see any reason it shouldn't be flipped around the other way.

I'll have to update the schematic and layout. I'd be interested to hear if reversing the cap makes a difference.

Installed and reversed a new capacitor on C12, works perfect now.

 

[bobthebuilder]

This is very interesting, thanks for the further investigation. I'll try to reverse C12 and see if my results are the same.

 

[Flipguitarist]

This is very interesting, thanks for the further investigation. I'll try to reverse C12 and see if my results are the same.

Good luck! Hope it works out. Let us know.

 

[Chuck D. Bones]

Don't put the old C12 back in. If it's damaged, turning it around won't solve the problem. Did you measure the voltages?

 

[Mojo321]

I have built three of these, and I haven't noticed any bass knob problem. But I will check and have my friends check theirs.

 

[Flipguitarist]

I have built three of these, and I haven't noticed any bass knob problem. But I will check and have my friends check theirs.

Like Chuck mentioned not all capacitors leak the same that’s why others didn’t have any issues. Installing a new capacitor the other way around fixed my issue.

 

[Chuck D. Bones]

Parts that are overstressed can fail immediately, someday, or never. It's those "someday" failures that you have to worry about because they will happen at the most inconvenient times.

 

[Flipguitarist]

Parts that are overstressed can fail immediately, someday, or never. It's those "someday" failures that you have to worry about because they will happen at the most inconvenient times.

I meant to say Chuck not Dave lol.

 

[bobthebuilder]

Finally got around to opening up the pedal and reversing the polarity of C12, as Chuck D. Bones suggested. I can confirm that this solves the bass control problem. It appears that the schematic is updated, so this issue should be resolved for future builders. Thanks again to everyone!