madbeanpedals::forum

General => Open Discussion => Topic started by: ddog on March 09, 2014, 11:17:51 PM

Title: Strat Volume Pot Problem
Post by: ddog on March 09, 2014, 11:17:51 PM
I was boxing up a pedal (Engineer's Thumb) and I noticed that if I roll of my strat volume, I actually bypass the volume knob all together. It goes roughly like this

0-1= Quiet
1-1.5 = Loud Scratching
1.5-2 = Volume  knob Bypassed
2-2.5 = Loud Scratching
3 - 10 = Gradual Volume buildup

At first I thought it was the pedal (grounding issues maybe), but then when I bypassed it, I realized it was my strat :( I changed my strings yesterday too. Any one familiar with the issue? Time to replace the pot? Any reccomendations on a replacement (current one is 250k)?

There is also a burning smell coming out of  my strat :o Maybe a broken cap??
Title: Re: Strat Volume Pot Problem
Post by: garfo on March 09, 2014, 11:42:56 PM
Try to plug the pickups straight to the jack output, if your signal is clean, then, try to clean the pot, all the solders, redo the wiring and go step by step:volume, tones etc.
Title: Re: Strat Volume Pot Problem
Post by: midwayfair on March 10, 2014, 02:24:34 PM
Sounds like you let a lot of DC into your pickups! Volume pot scratching is usually the most immediate sign of that. If you let too much in, it can fry the inductors. That's very bad.

Check the input cap on the engineer's thumb; replace it just to be safe. Measure the input for DC. DO NOT plug the guitar back in until you're dead certain that the input is safe and at 0 potential.

Check that the guitar is still working by plugging it straight into the amp.
Title: Re: Strat Volume Pot Problem
Post by: ddog on March 10, 2014, 05:42:46 PM
Guitar is still working. However the volume pot is pretty funky, at very low volume (2) it bypasses the volume pot as if its at 10. Past 2 it works as normal. I removed the Engineer's Thumb and its the same thing.

I think I know what happened. When I was boxing up the Engineer's thumb, the bottom of the PCB touched my input jack. This caused a pop and the signal dies off. Maybe it touched the input cap and that is what caused the current to go into my guitar.I isolated the backside of my PCB with electrical tape, so it no longer touches.

There is a burning smell coming from my guitar. I am really really hoping it is a blown tone cap or potentiometer, but the tone still works. How can I diagnose a broken inductor? I there a visual thing? Should I measure the resistence with a DMM? Thanks Jon!

EDIT: If there was damage done it is pretty evenly spread. All my pickups have the same issue occuring in the same spot
Title: Re: Strat Volume Pot Problem
Post by: ddog on March 11, 2014, 05:50:48 AM
Swapped out for a new pot - my strat is now as good as new  ;D
Title: Re: Strat Volume Pot Problem
Post by: jkokura on March 11, 2014, 06:03:37 AM
Yeah, it sounded to me like a bad pot. Glad it's working for you now.

Jacob
Title: Re: Strat Volume Pot Problem
Post by: Leevibe on March 11, 2014, 06:05:22 AM
Cheap fixes are the best! Hopefully you've let all the smoke out. :)
Title: Re: Strat Volume Pot Problem
Post by: garfo on March 12, 2014, 08:44:06 PM
Before you put a different pot, troubleshoot it, see if the pickup works, just wire straight from pickups to the output, if it works properly, then, time for a new pot.