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DIY Stompboxes => Building your own stompbox => Topic started by: Ripthorn on January 05, 2009, 01:27:24 PM

Title: How do I know if my pot is bad?
Post by: Ripthorn on January 05, 2009, 01:27:24 PM
So I just built a Dr. Boogey using the gaussmarkov schem and layout and I thought that everything was in place, but I plugged it in and got nothing.  I audio probed and found the problem is the treble pot.  I am getting nothing on pin 2 of the treble, meaning nothing getting to the output.  I have measured the resistance across the terminals of the pot and they seem to be in order, but I am baffled as to why I am not getting anything on pin 2.  I am getting signal on pins 1 and 3, but it seems like there might be something funny in the pot going on.  Anyone have any idea?  Thanks.
Title: Re: How do I know if my pot is bad?
Post by: R.G. on January 05, 2009, 01:35:27 PM
You put your ohmmeter between the wiper and one end, then watch the resistance as you turn the pot. It should change smoothly between one end and the other at a rate determined by the taper of the pot. Any open spots indicates the pot's bad. Then do the same from the other end.
Title: Re: How do I know if my pot is bad?
Post by: Ripthorn on January 05, 2009, 01:53:17 PM
Well, I checked and the pot is good, though between pin 1 and wiper I get a max of 15.5k and between pin 3 and wiper I get a max of 18.75k for a 20k pot.  Pin 2 goes to the volume pot, so the next logical thing was a short to ground, and lo and behold, one stray strand from my ground wire in pin 1 of volume made it's way to pin 2 of volume, shorting out the signal that pin 2 of treble was doing.  Thanks for the help in debugging, RG.  Thing works pretty sweet now, even though I feel stupid. :icon_redface:
Title: Re: How do I know if my pot is bad?
Post by: MikeH on January 05, 2009, 02:01:24 PM
Only one way to tell- smoke it.





Or check the resistance/continuity with your DMM.

;D
Title: Re: How do I know if my pot is bad?
Post by: BDuguay on January 05, 2009, 02:12:43 PM
Start by monitoring their grades at school. Also, check for moodiness or innappropriate social behavior. :icon_wink:
B.
Title: Re: How do I know if my pot is bad?
Post by: DougH on January 05, 2009, 02:38:26 PM
If water rises out of the bowl and floods the floor after you flush it...
Title: Re: How do I know if my pot is bad?
Post by: R.G. on January 05, 2009, 02:39:49 PM
... sniff... hmph.
ignoring spurious ignoble comments   :icon_biggrin:

No need to be embarassed. All of them are easy once you know the trick. It's the finding them that is tough, and you did that well.
Title: Re: How do I know if my pot is bad?
Post by: Paul Perry (Frostwave) on January 06, 2009, 05:48:34 AM
R.G. is right, the only person who never makes mistakes, is the person who never makes ANYTHING!