Paragon tone control

TSReppe

Active member
Hey guys!

Been working on a paragon and a weird problem has occured. Channel 1, which has a 1k at R3 is working flawlessly.

Channel 2(which has 100k on R17) on the other hand is doing something strange. It’s working all fine outside the enclosure, but when I put it in it gets gainy and bright. And the tone control no longer works as a tone control, but more as a gain control. If I turn it all counter clockwise the pedal goes silent, if I turn it up it gets loud and also brighter. I tried to find out when in the mounting process this happens. I can fasten the nuts on the channel 2 pots, but when I fasten the nuts on channel 1 it happens at a certain point.

Things I’ve tried:
- My inital thought was there might be an issue on C17, but I’ve checked the cap and made sure it is connected to both the Ch2 tone pot and vref.
- I’ve tried some testing with changing up the clipping, but result is the same. Ch1 is fine, ch2 weird.

Theories I can still try:
- The enclosure is painted on the inside so perhaps there is something there? When pots from both channels make a proper connection something happens? Strange it’s only on ch2.
- I‘m out 1u film caps so c8 and c19 is currently empty. I asked around and it seemed this shouldn’t be a major problem, which is why I went ahead with the build anyways. Still strange the issue is just on channel 2.

I can also ofc change r17 down to 1k, but I’m at that point where it makes sense to ask if anyone more knowledgeable can contribute anything.
 

Chuck D. Bones

Well-known member
It's customary to post pictures so we can see what we're dealing with.

Sounds like an intermittent short. Do you have dust covers on the pots?

I recommend removing paint on the inside around jacks, pots and switches so the pot shells are grounded.

C8 & C19 won't cause or cure this problem. Is everything else in accordance with the Build Docs?
 

TSReppe

Active member
Yeah removing paint was gonna be my next move. As you can see there are dust covers. Let me know if you spot anything I might have missed.
 

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TSReppe

Active member
It's customary to post pictures so we can see what we're dealing with.

Sounds like an intermittent short. Do you have dust covers on the pots?

I recommend removing paint on the inside around jacks, pots and switches so the pot shells are grounded.

C8 & C19 won't cause or cure this problem. Is everything else in accordance with the Build Docs?
To add to my last post. Everything else is in accordance with the build docs.
 

Chuck D. Bones

Well-known member
Were all of the pots mounted in the box while they were being soldered? If there is any misalignment, it could crack a solder joint when the nuts are tightened down.

Let's see the component side.
 

TSReppe

Active member
Were all of the pots mounted in the box while they were being soldered? If there is any misalignment, it could crack a solder joint when the nuts are tightened down.

Let's see the component side.
No they weren’t so I suppose that’s plausable. But shouldn’t problem still be there when I take it out of the enclosure if that was the case?
 

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Chuck D. Bones

Well-known member
Maybe, maybe not. Think about what's happening if the pots are misaligned and then they are tightened down in the box. Some of the leads are stressed and if there is a cracked trace or solder joint, it can open up. Take it out of the box and everything springs back.
 

TSReppe

Active member
Maybe, maybe not. Think about what's happening if the pots are misaligned and then they are tightened down in the box. Some of the leads are stressed and if there is a cracked trace or solder joint, it can open up. Take it out of the box and everything springs back.
I did a few things, hard to say what did the trick, but now the pedal works!

- Sanded down paint inside the enclosure
- Noticed a leg on ch2 tonepot was touching a led bezel, sawed of half the bezel to avoid that.
- Unsoldered both tone pots and put them back in making sure they had a better angle to avoid stress.
- Made the holes in the enclosure for both tonepots a little bit bigger to avoid stress on the pots.


Thank you for your help chuck, you’re a bloody legend!
 
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