Fixing the volume knob of a guitar pedal

[minnoq]

Hey all, new to this forum, have no experience in electronics and needing some help.

I'm a guitar player, and use a Voodoo Labs Sparkle Drive pedal in my setup (Voodoo Lab - Sparkle Drive). Was tidying up my room today and notice there was a lot of dust built up under the knobs. I couldn't quite reach under them to get the dust out, so cautiously used a flathead screwdriver to ease the knobs off. I started on the volume pedal, and it moved a short way before I couldn't get it any further - I realised there was a tiny screw in the back of the knob that I needed to unscrew to get it off. Clearly I wasn't careful enough, as after I took the knob off and dusted I realised I had done something wrong. The knob no longer stopped at the end of its rotation - just kept going and going. I plugged it into the amp and the knob had no effect - seemed to be at about 25%.
I decided to open it up, just to have a look, and after taking the back off I immediately noticed something was rattling around in there. I took it all apart, after popping out the volume knob i saw this:

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I found what had been making the rattling noise:

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Here's the back of the other knobs for reference:

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I assumed it would go together like this:

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However, the knob won't seem to go into that ??? part without some force, and I'm getting the idea that might not be what I need to do.

Anyone have any ideas? This might be simple, but I don't even know where to start.

And yes, I'm aware of how stupid I am for ever getting into this situation!

 

[Nigel Goodwin]

You need a new control, it's probable you've damaged it beyond reassembly - they aren't designed for that type of abuse.

 

[minnoq]

Ah, ok. What is a control? Is the entire part with the knob and the brown board?

EDIT: Assuming something was broken I reassembled the pedal minus the volume control, and it all works fine, except its constantly at 100% volume. So yeah, all is not lost, I hope this is something I can fix.

 

[Reloadron]

It looks like what you need is a 100K Ohm 2 Watt potentiometer (Pot). The unit is all one piece and you should be able to remove the remains of the old and replace it. Removing means de solder the 3 legs still on the board. I would not rule out repair but remove and replace is much easier. What it looks like you have is a thick film 2 watt 100K Ohm pot. Honeywell series 380 family should work. Made by many manufacturers and should be available from any electronics parts house. Typically about $10 USD.

Ron

 

[audioguru]

It is not a huge wire-wound 2W pot. It is a little carbon-composition 0.5W or 0.2W pot. It probably has an audio-taper not a linear-taper.

 

[KeepItSimpleStupid]

Those parts don't look bad at all. I've taken many controls apart 30 years ago.

The very first thing you need to do is straighen out the tabs.

The next real piece of information that you need is that the spring like wiper of the questionable piece must slide along the black carbon track.

On the cup shaped iece, there is a bump in the back. This is part of the stop. If the control isn't placed properly, it will sit on the stop.

Once you get it put back together without bending the tabs back, the control should stop within about a 270 deg rotation. It's conceiveable that if missassembled, the control would only rotate about 30 deg.

 

[Reloadron]

It is not a huge wire-wound 2W pot. It is a little carbon-composition 0.5W or 0.2W pot. It probably has an audio-taper not a linear-taper.

On second look with some perspective they are pretty small. I saw the metal cans and jumped on 2W. Anyway, they can be had or just as covered with directions from KeepItSimpleStupid reassembled.

Ron

 

[Jon Wilder]

I work for Voodoo Lab tech support. You can give us a call at (707) 545-0600 ext 110 and we can set up an RMA to have you send it into us for repair. If you've never desoldered components from a plated through board it can be a very trying task without damaging board tracings.