Help - my B pedal/6th string is driving me crazy

[Bill Monk]

My 6th string raises and lowers have driven me crazy ever since I started trying to play.
Today I backed off the tuning nuts on everything that affects the 6th string except the B pedal, and here's what I found.

Snap the B pedal down (no hard, just quick), the A note is in tune. Play a quick B pedal with any other change, before any other change, after any other change. The A is in tune, plenty good enough to satisfy me.

BUT - slowly press the B pedal, and the 6th string A note ends up flat. Doesn't matter how gently or hard you press once it hits the stop, it is flat. This happens no matter what other changes have already happened, or happen along with the slow B pedal, or happen after the slow B pedal. That 6th string raise ends up flat.

Now snap it down: back in tune.

Same thing happens if you reach under and move the cross shafts by hand. Quick = in tune. Slow = flat.

I'm stumped. When the pedal hits its stop, the string ought to be stretched the same amount whether it go there fast or slow, so the note should be the same. But it's not.

And it's not just something you'd barely notice. It's between 5 and 6 Hz difference, measured on a Peterson VS-1 strobe tuner. And it's NOT cabinet drop: if I press down really hard on A & B, it might drop 0.5Hz. Not 5-6 Hz, which is not just a little out, but WAY OUT OF TUNE.

Any ideas what's going on, or how to fix it?

[Jon Light]

Couple of thoughts---

--Is there slack at the nylon tuning nut? This should be backed off enough that there's a tiny bit of slack--make an adjustment to increase the amount of pedal travel if you can't get up to pitch.

--Is the roller nut moving free and clear?

--Is the string fresh?

--Have you considered using a wound string? (much less sensitive to minor mechanical fluctuation)

It would help to know what kind of guitar this is.

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edit:

an addition thought---is the guitar well maintained and lubed? Do the cross shafts have some lateral wiggle slack to them (as they should)? Seasonal humidity changes can shrink down or swell up the body and pinch the cross shafts. I'm picturing a situation where they are binding with slow movement but are traveling farther with the momentum of the fast pedal stomp.
<FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Jon Light on 10 August 2002 at 05:28 PM.]</p></FONT>

[Gil Berry]

Had the same problem -- turned out to be in the changer mechanism. The change finger had worn a groove where it was supposed to "slide"...FWIW...(I cleaned mine up with emery cloth, but really need to replace the aluminum parts with stainless to correct the problem...worried about what it will do to the tone, though...)

[Earnest Bovine]

Bill,
All my guitars have that problem (some worse than others). It confuses me for the same reasons that you mentioned.
Cleaning/replacing the changer didn't help. I don't see where there could be significant binding or friction. So I'm stunmped. A push and release of the raise bar or lower bar leaves the string at the higher pitch , the pitch you get by pushing the pedal fast.

[richard burton]

If it is an 'all pull' guitar, try tightening the lower return spring on string 6.