Pitch Return Problem-- please help me understand

Jon Light · From: Saugerties, NY

I have read about this known issue for years but I've never been able to understand or focus on the fix and it has not really pertained to me until now. I'm hoping the forum can help me get a handle on it.

On my Fessenden U-12:

I have added a 6th string compensator (raise) to the A pedal to compensate for 6th string cab drop. (I just changed back to a plain string here after a number of years and the drop is a lot more than it was with the wound string, as we all know).

The Problem:

If I have AB down and release the B pedal, the compensator hangs the 6th string very sharp until I release the A pedal.

Can anyone help me to understand the fix? I am pretty much up to the task of rigging mechanical stuff (springs, brackets). I just can't grasp what needs to be done.

Thanks.

Jack Stoner · From: Kansas City, MO

I don't understand why compensators of that type are really needed. The only time I have "cabinet drop" is on a tuner. In actual use I don't "hear" any cabinet drop (maybe I'm compensating for it with the bar and don't realize it).

I played for 20 years, with guitars that had it, and didn't even know there was such a thing as "cabinet drop" (detuning). I only found out about it after Winnie Winston published an article about it and some measurements he took at St Louis, in a PSGA newsletter.

Jon Light · From: Saugerties, NY

Jack--I do not understand your post.

If it did not bother me, do you believe I would be posting this?
If I did not want to understand the issue better, do you think I would be posting this?
Do you believe that the sort of response that people write to beginning players on this forum is useful to someone that you know has been here on the forum for 15 years?

I do not understand.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

I guess I'm not clear exactly what your compensation goal is. I would put a 6th string compensator on the A pedal to counteract the effect of cabinet drop on the 6th string caused by two main things - A-pedal alone and A+F combination. If you just wanted to compensate for the effect of A-alone on 6th string drop, you'd just tune it exactly so that when A-alone is depressed, string 6 is perfectly in tune.

Since there should be, in principle, more 6th string cabinet drop from A+F than A alone, it strikes me that one can't get perfect compensation for both A-alone and A+F with a single compensator on 6 without doing something else.

So I presume that you're tuning the compensator to compensate for A+F, the worst case? If so, then I'd expect A-alone to pull string 6 a bit sharp because the compensator is pulling further sharp than required for just that change. So it strikes me that there has to be some compromise on how much compensation to apply to get it to work well with both changes. Since compensation is a second-order effect, it seems that one should be able to get a pretty good result by splitting the difference between the A and A+F changes. Or perhaps if it's extremely sharp on the B-release from A+B, something is not releasing completely when you are releasing B - perhaps some hysteresis, perhaps something sticking?

I guess one could add two compensators to string 6 - an A-pedal compensator tuned just for the A-pedal, and then a second compensator on F to correct for the A+F combination, and then tune each exactly, provided one has enough free raise changer holes on string 6.

There may be some other approach to handle your issue, but I would need to understand exactly what you're trying to accomplish, I'm just speculating on what you're trying to do.

Jon Light · From: Saugerties, NY

Thanks Dave. Yes, the compensation is for both the A and the A/F but a compromised compensation for both combinations would be sufficient. My problem is not here.

It is in the physical issue that I've read about many times in the past where a string is double raised or double lowered and when one of the pedals/levers is released, the other one hangs up, not in tune, until released. It may be a hysterisis issue but I'm not sure. I thought I'd read that there was a simple solution but from studying the undercarriage I cannot imagine or remember what it might be.

John De Maille · From: On a Mountain in Upstate Halcottsville, N.Y.

I don't have a 6th string compensator,but, if I did, I would tune the 6th open first, then press on the the A pedal and tune the comp, then press the A+ B, then release B and see if there is any binding with the B changer finger. There has to be something stopping it from returning to the comp pull. If you can't figure it out, give Jerry a call. He's always willing to help. After all, who would know better about a Fessenden steel.

Peter den Hartogh · From: Cape Town, South Africa

Jon, I believe I had a similar problem.

If two crossrods are very close together, the rotating bellcrank bottoms can touch each other provided they line up with the same string. The bottom of the bellcrank is the part of the bellcrank between the body of the guitar and the crossrod.

When I checked my bellcranks I noticed that the bottom of the bellcrank on the pedal-crossrod was touching the bottom of the adjacent bellcrank on the knee-crossrod. I solved it by changing the pullrod positions, which reduced the rotation.

Your problem might be something else, however.

Jon Light · From: Saugerties, NY

Thanks Peter. Pretty sure I'm picturing what you describe and I've looked it over and no, it does not apply. Thanks.

Pete Burak · From: Portland, OR USA

Jon,
Your problem if I understand correctly:
You raise G# to G#+ on the A-pedal.
You then raise G#+ to A on the B-pedal.
When you release the B-pedal, G#+ is way sharp.

It is Hysterisis.
Here's the proof...
This is not specific to an S12U, but since you are using an S12U try this...
Watch this on your tuner:
String-9 open (on S12U) is B.
Raise it to C# on the A-pedal (or A+B, however you usually tune it).
Without releasing the A-pedal, raise string-9 to D with your knee lever.
Now release the D back to C#.
The C# will now be way sharp on you tuner, due to hysterisis.
If you release then re-enguage the A pedal, the C# will be back to the original note.

You can see the same phenomona on string-4-E (on any E9th Steel, as far as I know).
Raise it to F (check tuner).
Without releasing, raise it to F#.
Release from F# to F... The F is now way sharp.
Release the F then re-enguage, the F is back to the original note.

With regard to the B-string-9, At the point in the test when the C# is really sharp, you can actually reach under and press on that changer finger and return it to the original C#.

I once showed this to Don Christianson of Sierra.
He wanted to devise a fix with something similar to a spring loaded toggle like you sometimes see on a screen door (springs open when you push the door open, springs tightly closed when you close the door).
We never followed through with that.
Maybe someone has figuerd out how to eliminate hysterisis by now???... Not sure.
Sorry I don't have a fix other than the ol' quick release and re-enguage.

Jack Stoner · From: Kansas City, MO

Jon, I'm not saying there isn't any detuning of the string. Just that I've never had a problem playing with whatever "cabinet drop" I have, and thus no need for any extra compensator rods.

Jon Light · From: Saugerties, NY

Pete--bingo. Yes---I didn't take the time to remember where else on the guitar I knew this happened but yes indeed, those are other examples. I am spending time playing with the undersides and observing. I've got all day. I'm waiting for my voila moment.
You may be 100% correct that it is a hysterisis issue but I'm observing some interesting cross shaft & bell crank behavior that I want to better understand.
Thanks!

Pete Burak · From: Portland, OR USA

Jon, I recall reading on the Forum that there have been some Fessy's that had cross-shaft binding due to aging of the wood aprons over time.
That may be an issue in this case, and fwiw I would get that fix directly from JF.
I think there was a replacement bushing and/or cross-rod.
Pete

Jon Light · From: Saugerties, NY

I'll look into that, Pete (although I don't think I'm seeing evidence of that here.)

Fessendens do require seasonal examination to address possible cross shaft binding in the bushings due to cabinet contraction--a general maintenance check-list sort of thing.

mike nolan · From: Forest Hills, NY USA

John,

Just went around and around with something similar.

Does the Fessy have pedal return springs?

I had a situation where the weight of pedals was keeping raises changes from returning properly. In my case, when I pressed pedal B, I could see my P7 moving. When I released B, the weight of P7 kept string 6 in a slightly sharp state. If I manually lifted P7, string 6 came back to where I wanted it. I added a pedal return spring to P7 and the problem went away.

And this only happens in the playing position.... won't happen on the bench.

Jon Light · From: Saugerties, NY

Good one, Mike and in fact there is a lot of interactivity between my P7 and the B pedal in terms of rattle and general slack rod movement. But my problem does exist on the bench so the resting pedal weight cannot be a factor here.

I'm seeing interesting shaft movement, taking up slack and not returning until all is released....I have to believe that with something so obviously physical, the cause & solution will reveal itself to me.

mike nolan · From: Forest Hills, NY USA

Interesting.... maybe look at other B6 side changes being involved somehow.

I do Get Jack's point.... but the Uni is a very different animal than a D-10, or S-10, and there are a lot more complex interactions going on. There are a lot more tuning adjustments to make everything play nice... so the issues are not so easy to "play around". I have never seen a 12 string of any flavor without 6th string detuning issues of some sort. I think that it is the result of changer axle flex combined with cabinet drop. Then add in the multiple pulls all on the same neck.... I have 37 pulls on my Uni.

Keep us posted.

richard burton · From: Britain

I had exactly the same problem when I put a compensator on a Carter, and have my own theory why this phenomenon
happens, which is all down to cross-shaft deflection.

When the A pedal is pressed, it raises the usual two strings, 5 and 10, and also very slightly raises the 6th string, to bring it back into tune due to cabinet drop.

This slightly extra loading on the A cross-shaft causes it to deflect more than if there was no compensating rod to the 6th string.

When both A and B pedals are pressed, the slightly extra loading on the A cross-shaft is not there (because the 6th string has been raised by the B pedal), so the cross-shaft deflection is slightly less.

When the B pedal is released, the 6th string is held by the compensating rod (from the A pedal) and, for reasons that I don't quite understand, the A cross-shaft does not deflect any further (even though it now has the 6th string back in the equation), the result being that the 6th string is way sharp.

Jon Light · From: Saugerties, NY

Richard--my day's worth of work on this is strongly leading me in this direction. I entered this thing with some of that thought in mind because of what I thought I recalled reading here. It seems very possible to me that you were one of the people publishing this hypothesis/finding. Close examination shows unquestionable flex in the cross shafts as well as slightly elliptical rotation.

I have noticed that some other steels (Zum?) have similar looking shafts and use nylon 'bumpers' on the center, rounded part of the shaft, presumably as an anti-flex treatment. I am wanting to attempt something like this.

mike nolan · From: Forest Hills, NY USA

Yeah Jon,
The bumpers.... and this thread

http://steelguitarforum.com/Forum5/HTML/012682.html

or here

http://steelguitarforum.com/Forum5/HTML/003884.html

there was more detailed stuff on the O rings, by Carl Dixon.... which you might search for.

Jon Light · From: Saugerties, NY

Cool, Mike. Yes--I remember these discussions. I probably have them bookmarked somewhere. It was always a subject I expected to come around to wanting to understand better. Time has come today.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Jon, the problem with cross shaft flex is normally only a problem on double-bodied guitars. Single-wide guitars have shorter cross shafts, and usually don't exhibit a serious flexing problem (though the elliptical movement you mention suggests a bent rod, or worn bushings). I'd suggest first eliminating as much of the hysteresis problem as possible. This means that the nut rollers should be well lubed and very free, and that the strings must pull absolutely straight, or in-line, to keep sideways roller-friction out of the picture. Then if there is cross-shaft flex, it can be reduced by the bumpers that Zum uses, or some similar method.

Once all that is checked or corrected, you can move to concentrating on the compensators. None of my guitars has or needs compensators, but I know some guitars do...and from what I have heard, the o-ring approach to "nudging" the compensated string instead of a rigid micro-change seems to work best.

Lastly, don't be too hard on Jack. We all speak mostly from our own experience, and one shouldn't get upset with those who are spending their time trying to help, or just offer suggestions. I had one friend (Bobby Sparks) that had what he termed "terrible cabinet drop" (almost 10 cents). But when I played his guitar, it was only 4-5 cents. The difference was caused by the excess force he was putting on the pedals. He worked on this "problem" of his heavy foot, and improved it significantly, such that he removed a compensating device he had previously added to "fix" the problem.

Jon Light · From: Saugerties, NY

Good stuff, Donny. In all of this I failed to mention that it is indeed a double body.

I am trying to get a handle on the o-ring thing. I am uncertain whether it address my 'raise/raise' issue as opposed to the 'raise/lower' string return issue. I am studying this.
All other factors are well maintained--rollers, straight-line strings.
I regret that this all is an outgrowth of changing from a wound 6 to a plain 6. All was well with the wound excerpt for the excessive lever travel for the full step lower that finally got to me.

As to Jack--it is a button that I have less and less patience to have pushed. If I have carburetor problems, I do not consider 'walk' to be an attempt at a helpful answer, nor am I interested in arguing the question of whether or not I actually am having a carburetor problem unless I am obviously driving a fuel injected car. Jack is a valuable and esteemed member of this forum with knowledge and experience far beyond my own. I do not feel he did much justice to my question. If I was a jerk....that is not something I am proud of but I've got the right to be ornery now and then.

Pete Burak · From: Portland, OR USA

Hi Jon, Any update?
Question... When you tune string-6 to the desired pitch, how flat does it go when you enguage A+F?
Is the A+F position the only reason for having the compensator?

Jon Light · From: Saugerties, NY

Hey Pete. Haven't had time for much. I need to play so I'm trying to put this on hold until the weekend when I expect I'll go back to the wound string (some rerodding required). I'm getting around a 9 cent drop on 6 with the A pedal and around 12 cents with A+F. It is excessive but I don't know what I can try to reduce the drop and I'm not optimistic I can solve the compensator problem. I just wish the wound string didn't have such a long throw on the G#>F# lower. Oh well.

Jon Light · From: Saugerties, NY

Actually, I just threw the comp. pull on the F lever. It has me satisfied for the time being. Far fewer things that I do that invoke the raise/raise scenario. It'll tide me over.

Forum Index > Pedal Steel		Next oldest topic :: Next newest topic