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Wah Pot Trouble

Started by spaceace76, June 16, 2008, 09:07:44 PM

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spaceace76

I was experiencing some strange noises with my v847 equipped with a blackbear pot, odd scratches, and the taper sounded off. After seeing this thread I cleaned the pot out with deoxit:

http://www.diystompboxes.com/smfforum/index.php?topic=68441.0

That cleared up the scratches, but the taper was still weird, and now that the scratches are gone I can hear how odd the taper is. Essentially, the entire taper is bass until near the end, at which point a pop transitions between bass and treble. From what I remember before the pot was acting up, the bass/treble sounds it's putting out now are the full heel/toe sounds. So my pot only does full-on bass or full-on treble. I switched out this pot for a hotpot I had laying around, and the wah worked fine.

I'm 85% sure that this isn't something I did after opening the pot to clean it. I definitely noticed a similar sound from before I cleaned it out, but since the scratching is gone I could hear what the wah was doing more clearly.

So, did I screw something up? Did my pot just crap out on me? What can I do to fix it?

Many thanks  for any suggestions

mistercoffee1

If you're pretty sure you've got it all cleaned out, and you noticed this taper before you cleaned it, and your hotpotz I doesn't have this weird taper, then I'd say the pot is off.
Was it always this way even when you first got it?  How old/new is it?

petemoore

  Put DMM leads on lugs 1/2, slowly rotate and look for huge jumps in other wise steadily rising or falling resistance, pot probably has some taper [R rises faster toward one end of the shaft travel or something] but it should give fairly smooth rising and falling resistance.
  Do the same between lugs 2 and 3.
  compare that to what other pots 'do when' [R at specific shaft rotation points, imprecise but you can get a feel for it]
  Labor intensive as far as note-taking...take notes how the DMM responds to the pots and how the wah responds to the pots, choose a taper to use or diddle with [using tapering or stop resistors].
  I had a 200k pot I like as 100k pot [100k resistor parallel to wafer, across lugs 1 and 3].
 
Convention creates following, following creates convention.

spaceace76

I've had it for about a month, but it was dead quiet when I first installed it. A few jam sessions later and it started acting funny. I'll definitely check it with my multimeter and post the results, thanks petemoore.

spaceace76

Alright I finally got time to check it out with a multimeter. The pot appears to be rising in ohms normally until about 3/4 of the way through the taper, at which point I get odd ratings like 215.8k or 125k, after which the meter says "OL" which is what it says when it can't get a reading or the reading is out of the selected range. I changed the range around and it seems like the meter just can't read it. I've also noticed that a portion of the bottom of the taper just reads 0.00, so only half of the actual taper is reading properly. I tested my hotpot and it ramps up from about 2k all the way to 100.9k. So, even though my meter is reading from 0-100 on the pot, it seems like the taper is way off, especially when it starts to jump around at the end. This doesn't really explain why it stays in bass the entire time, though. Any ideas?

spaceace76