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Author Topic:  Lower comes back sharp
Eric Gross

 

From:
Perkasie PA, USA
Post  Posted 22 Apr 2011 10:44 am    
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Hi All,

About a year ago I took the plunge into psg by buying a no-name psg from a pawn shop in Philly. It took awhile, and without this forum I never could have done it, but it is working for the most part now and I have actually done a couple of paying gigs with it.

The guitar is setup in A6 tuning (best I could figure it's original intent based on existing copedant setup -- thanks SGF!). When I do a lower on the 5th string F# to E, then release the pedal, it always comes back sharp. I can pull on the string and it will come back into tune. I have tried to isolate it and it seems more likely it is due to the roller/tuners then from the changer (triple raise/lower). But i am no expert -- can anybody offer some advice?

Thanks,
Eric
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Bent Romnes


From:
London,Ontario, Canada
Post  Posted 22 Apr 2011 5:28 pm    
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Eric, I believe this could be string hysteresis. This is sometimes fixed by making sure there are no burrs on the roller and also you want to lube the roller and make sure it is rolling freely
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Jeremy Craft


From:
Portland, Oregon
Post  Posted 22 Apr 2011 8:24 pm    
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Try Bent's advice first. If you still experience hysteresis, loosen the tension on the return spring until the string returns flat, then gradually tighten it back up until it returns in tune.

If the return springs are not adjustable, you might have to find a spring or springs with lower tension, and swap them for the ones that are there now.
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Eric Gross

 

From:
Perkasie PA, USA
Post  Posted 23 Apr 2011 12:47 pm    
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Hi,

Thanks to all for the advice. I tried lubing the roller, but when rolling it freely with no string attached it does not roll straight, I guess the shaft is bent. Also, there is another roller that is flattened on one side, it looks like something dropped on it.

I would like to replace the rollers, but don't know how this assembly is attached. Is it all one shaft that holds the rollers, or is each roller on an individual shaft? And how is the shaft held in place?

Pictures attached, hopefully someone can identify this setup.

Many thanks in advance(and sorry for the rookie questions),
Eric




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Bent Romnes


From:
London,Ontario, Canada
Post  Posted 23 Apr 2011 5:53 pm    
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Eric,
Usually there is only one shaft running thru. That's what it looks like on the pics.

It sounds like your rollers and shaft are due for a good cleaning and touching up.

Here is what I would do first, before you run out and buy new rollers.
-Take the strings off. The shaft is likely sitting in the groove by a wee bit of a tight fit. With a small slotted screwdriver, put the blade up under the shaft sticking out and very carefully , tap the handle with a small hammer. This has to be done with care so the rollers don't go flying. When you get the shaft off, take the rollers off the shaft one by one.

Have little tags ready with string number on them so you can label each roller in case they are gauged to the string. Get hold of some de-greaser at a bicycle shop.
In lieu of this, try using paint thinner and alcohol. You must get all the old lube and dirty residue off all the parts, especially inside the roller holes.

Now for the roller that is flat on one side. Get yourself a fine file. Gently file off any nicks, protrusions and burrs. If this damage is on the round part, try to follow the contour of the roller with your file. Better still, if you have some way of holding the roller steady, use a strip of fine sandpaper on the round part, if needed.

Don't forget the shaft groove in the nut. Maybe some paint thinner on a rag, moving the rag in a sawing motion down in the groove.
When everything is clean and dry, apply a thin film of light oil to all the parts, such as gun oil, sewing machine oil or 3-in-1. Do NOT use WD40!

Reassemble.

The roller with the flat spot - if it will interfere with the string, give that roller a half turn away from the string.
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Brint Hannay

 

From:
Maryland, USA
Post  Posted 23 Apr 2011 8:55 pm    
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Attention to the roller nut can only be a good thing, but if the roller was hanging up, wouldn't that cause incomplete response, i.e. cause the string to return flat from a lower?

Returning sharp from a lower is a different and more puzzling phenomenon, as it is counter-intuitive. After all, after you bring a string up to a chosen tension (that is, tune the string), in principle the string under tension doesn't "want" to gain additional tension; it wants to relax.

It seems to me it should be mentioned that, as far as I have gathered, the general consensus is that something intrinsic (what exactly is not entirely clear) in the way the structure and behavior of PSG mechanism in general interacts with the string, regardless of specific design details, adjustment or maintenance condition, causes strings to return sharp from lowers.

It is maintained that the keyless design eliminates this phenomenon, but my keyless GFI does not confirm that assertion.

In other words, whatever steps one may take to make the mechanism work efficiently and smoothly, over-return from lowers seems to be simply a fact of life, and a solution to the problem, at least with keyhead steels, has not been found. But if a player accepts it, it can easily be lived with.

If anyone can refute what I've said, and testify to an approach to design or adjustment that in fact eliminates over-return, I'd be glad to learn that I'm wrong. Smile
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Georg Sørtun


From:
Mandal, VA, Norway & Weeki Wachee, FL, USA
Post  Posted 24 Apr 2011 12:32 am    
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Brint, hang in the keyhead rollers will result in strings returning sharp after lower and flat after raise. This is something I have tested thoroughly and experienced for decades on my Dekley, in addition to modeling it in software. My newly acquired GFI keyless has even more of this hang, simply because there is no rollers, just a fixed bolt for the strings to slide over.

The reason for the "wrong way" hysteresis is that the length of string past the rollers gets stuck flat from a lower-action (sharp from a raise) when a roller hangs on release, so the length of string between roller and bridge will stay sharp if a roller hangs ever so slightly when released from lower-action. This imbalance in tension lasts until string-vibration gets strong enough to shake the roller or the string itself loose so string tension becomes equal on both sides of keyhead rollers. Add to this that the string itself has hysteresis and needs time to settle, and one can see why a roller with the slightest tendency to hang doesn't immediately return to perfect balance and get "stuck" slightly off.

On a keyed PSG the center strings have more string-length past the rollers, plain strings with short change-travel tend to sound most out of tune after return. Plain 5th and 6th strings will therefore have most noticeable hysteresis with all else equal on keyed PSGs.


I clean up the rollers on the Dekley when the problem becomes noticeable, which keeps it going without audible hysteresis for months. A straw-nosed spray-box with super-thin lubricant (for electrical switches and such) solves the problem with incomplete return for hours when I can't take the time to dismantle and clean the rollers.

No way to "cure" my keyless GFI for more than minutes - just long enough to pin-point the cause of the problem, using thick grease to make the most problematic strings slide. That solid bolt is hopeless unless the string-length behind it is kept extremely short and the strings run almost flat over the bolt for minimal friction.


Rollers that are made with tight tolerances on their shaft and then lubricated, will hang more and more in the lubricant as it dries out and thickens with time. The rollers simply "cling" to the shaft unless the lubricant is super-thin/-fluid with no dirt particles.

Clean (no lubricant used) rollers that are very loose on their shaft, and that are tapered inwards from center towards the edge so they don't rub against the sides in the roller-mount, result in less to no hysteresis. This is because loose rollers with no lubricant to "cling" to simply roll ever so slightly out of position on the shaft to even out string tension at the moment of full return from raise or lower, and continue off as the string settles. This minute offset can only be heard if one plays open (no bar), and hardly even then since the offset is in the 1/10 - 1/20 millimeter range if one hasn't overdone the "loosening".



With most regular and not too corrupt keyhead rollers, it is enough to push the bar quickly down at the moment of full release after raise/lower to shake the rollers and equal out string tension over them. Not always easy to include such a "shake" while playing though.


One of the effects of the "tuned O-ring hysteresis preventors" (or whatever one should call them) found on some PSGs, is that they act more or less in sync with the string-settling. Thus, the keyhead rollers continue to roll while the string settles, instead of halting too early and get "stuck".


When raising or lowering a string it settles "in reverse", so there one has the effect that those "O-rings" have on release in the string itself. Thus, no sharps or flats there unless the PSG mechanism is completely clogged up with old oil and dirt.


FWIW, I tested/measured all this along with all else that might affect perfect stability back when I modified my Dekley - 88 to 93, and apart from that the keyhead rollers still are a bit tight on the shaft and need thin oil now and then, that PSG has no audible hysteresis apart from the unavoidable string settling. It doesn't have "O-rings" either since it doesn't need them, the floating neck I put on it "shakes and rattles" enough to make strings settle in tune - as long as the rollers don't cling to their shaft.
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Earnest Bovine


From:
Los Angeles CA USA
Post  Posted 24 Apr 2011 8:10 am    
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Georg Sørtun wrote:

The reason for the "wrong way" hysteresis is that the length of string past the rollers gets stuck flat from a lower-action (sharp from a raise) when a roller hangs on release, so the length of string between roller and bridge will stay sharp if a roller hangs ever so slightly when released from lower-action. This imbalance in tension lasts until string-vibration gets strong enough to shake the roller or the string itself loose so string tension becomes equal on both sides of keyhead rollers. Add to this that the string itself has hysteresis and needs time to settle, and one can see why a roller with the slightest tendency to hang doesn't immediately return to perfect balance and get "stuck" slightly off.

On a keyed PSG the center strings have more string-length past the rollers, plain strings with short change-travel tend to sound most out of tune after return. Plain 5th and 6th strings will therefore have most noticeable hysteresis with all else equal on keyed PSGs.


Yes, exactly right.
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Brint Hannay

 

From:
Maryland, USA
Post  Posted 24 Apr 2011 10:58 am    
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Georg Sørtun wrote:
My newly acquired GFI keyless has even more of this hang, simply because there is no rollers, just a fixed bolt for the strings to slide over.

Thank you for that--I have had wrangles with one Forumite in particular who insisted that there must be something wrong with my particular GFI keyless.

Now we're getting somewhere!

My uneducated theoretical speculations:

Clearly, uneven distribution between the two segments of string-- 1) between changer bridge and nut, and 2) between nut and above-nut attachment point-- of changer-induced changes in tension is what leads to over-return. My experience with the GFI made me further think that this holds true regardless of the length of the above-nut segment. There is an above-nut segment on the GFI; it's very much shorter than any found on a keyed guitar, but the GFI has over-return comparable to my keyed guitars.

But if nut drag is the cause of uneven distribution of tension change, why does it only affect returns from lowers? Once a string is stretched in, I have never found a tendency for strings to return flat from raises, while a well broken in string still over-returns from a lower.

I speculate that the behavior has more to do with greater hysteresis (lag in recovery of former state after a change) of a short segment of string (e.g. above the nut) under x amount of tension compared to a long segment (e.g. "speaking" segment) under the same tension. And I suppose that this hysteresis ("reluctance" to change) would apply to regaining tension, as anything under tension is naturally quite willing to lose tension.

Hence the above-the-nut segment's greater reluctance to regain tension after a lower makes the speaking length overcompensate, while neither segment is reluctant to lose tension after a raise.

All right! I hear you all snoring!
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Georg Sørtun


From:
Mandal, VA, Norway & Weeki Wachee, FL, USA
Post  Posted 24 Apr 2011 12:48 pm    
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Brint Hannay wrote:
I have had wrangles with one Forumite in particular who insisted that there "must be something wrong" with my particular GFI keyless.
You have a "perfectly normal" GFI keyless ... I'm afraid Sad

Brint Hannay wrote:
But if nut drag is the cause of uneven distribution of tension change, why does it only affect returns from lowers?
One reason is that a string releases much more energy as it settles coming down from higher tension, than it does when coming up from lower tension. Higher energy release kicks the string better past the roller/bolt, and then a string "released down" settles at a slightly higher pitch - usually right on target - within a fraction of a second.

Part of the equation is that the less of an angle a roller has to rotate to balance tension on both sides, the less likely it is that it will roll that distance if it halts or hangs first - the result of the phenomenon known as "initial friction". The lesser energy released in a string coming up from lower, means there is less energy to overcome this "initial friction" to roll - or slide on the GFI keyless - past the hang-point.
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Eric Gross

 

From:
Perkasie PA, USA
Post  Posted 24 Apr 2011 7:20 pm    
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Hi All,

Thanks very much for the great responses, I will try popping off the rollers and hopefully can get it working a little better.

I didn't realize that learning the inner workings of a pedal steel would be like taking an advanced physics course!

Thanks,
Eric
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richard burton


From:
Britain
Post  Posted 25 Apr 2011 7:53 am    
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We're all talking about the roller nut, but what about the changer finger?

There is a small amount of string slip during raising and lowering (that's why the fingers end up with grooves in them), so there will be a slght 'hang' at the changer finger, as well as at the nut.
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Georg Sørtun


From:
Mandal, VA, Norway & Weeki Wachee, FL, USA
Post  Posted 25 Apr 2011 8:23 am    
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Richard, you are absolutely correct, the slip over the changer is part of the hysteresis problem.

I haven't found a permanent fix for that slippage - short of redesigning the entire PSG that is, but on my preferred PSG I routinely apply tiny amounts of super-thin lubricant on the strings over the bridge/changer and can hear the effect.
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Eric Gross

 

From:
Perkasie PA, USA
Post  Posted 7 May 2011 6:42 am    
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Hi All,

Thanks so much for all of the great input. I finally had time to take apart the roller assembly, It is cleaned up and ready to go back on. A couple of the rollers had some imperfections so I smoothed them out, and of course one was out of round from being hit with something, so that one I filed back into shape, and used a small file to cut the groove.

Now I am ready to re-assemble. However, take a look at the picture, I notice on the changer there is some wear from strings. I assume this is normal and I should just live with it, but wanted to check with the experts to see if there is anything that can be done. It was hard to get a picture to show what it really looks like, there is string wear which kind of looks like ruts or rutting.

Thanks,
Eric

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Ned McIntosh


From:
New South Wales, Australia
Post  Posted 7 May 2011 5:28 pm    
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Eric,

I may be stating the blindingly-obvious here, but from the photos, your "no-name" steel looks like an MCI, a very highly-regarded steel indeed. With a little tender loving care, some polishing and maybe a new part or two you may well find you have a real gem there. There are plenty of people on the forum who can give you good advice how to get this unit back in tip-top condition.
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Eric Gross

 

From:
Perkasie PA, USA
Post  Posted 10 Jul 2011 8:41 am     works now
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Hi All,

I have been laid up a bit with a pinched nerve, so it took a while to get to this. The good news is, I have the lower working now.

I would like to thank Jim Flynn of Lone Star Steel Guitars for helping. It turns out Ned's post was right on the money, this psg is an MCI style that was made by Mr. Flynn some time ago. He sent me an email offering to send some replacement rollers free of charge. I asked if I could just buy a whole roller nut assembly which he provided, along with some rods so I can move some pedals and the copedant. The quality of these parts is outstanding.

Bottom line is the guitar is working great now, thanks for all of the great advice and support.
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Franklin

 

Post  Posted 10 Jul 2011 4:46 pm    
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Brint Hannay wrote:
Attention to the roller nut can only be a good thing, but if the roller was hanging up, wouldn't that cause incomplete response, i.e. cause the string to return flat from a lower?

Returning sharp from a lower is a different and more puzzling phenomenon, as it is counter-intuitive. After all, after you bring a string up to a chosen tension (that is, tune the string), in principle the string under tension doesn't "want" to gain additional tension; it wants to relax.

It seems to me it should be mentioned that, as far as I have gathered, the general consensus is that something intrinsic (what exactly is not entirely clear) in the way the structure and behavior of PSG mechanism in general interacts with the string, regardless of specific design details, adjustment or maintenance condition, causes strings to return sharp from lowers.

It is maintained that the keyless design eliminates this phenomenon, but my keyless GFI does not confirm that assertion.

In other words, whatever steps one may take to make the mechanism work efficiently and smoothly, over-return from lowers seems to be simply a fact of life, and a solution to the problem, at least with keyhead steels, has not been found. But if a player accepts it, it can easily be lived with.

If anyone can refute what I've said, and testify to an approach to design or adjustment that in fact eliminates over-return, I'd be glad to learn that I'm wrong. Smile


Brint,

You analyzed the problem well......Return Compensators completely solves this problem. I suggest putting one on each string that is raised and lowered.

Paul
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Franklin

 

Post  Posted 10 Jul 2011 4:48 pm    
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Brint Hannay wrote:
Attention to the roller nut can only be a good thing, but if the roller was hanging up, wouldn't that cause incomplete response, i.e. cause the string to return flat from a lower?

Returning sharp from a lower is a different and more puzzling phenomenon, as it is counter-intuitive. After all, after you bring a string up to a chosen tension (that is, tune the string), in principle the string under tension doesn't "want" to gain additional tension; it wants to relax.

It seems to me it should be mentioned that, as far as I have gathered, the general consensus is that something intrinsic (what exactly is not entirely clear) in the way the structure and behavior of PSG mechanism in general interacts with the string, regardless of specific design details, adjustment or maintenance condition, causes strings to return sharp from lowers.

It is maintained that the keyless design eliminates this phenomenon, but my keyless GFI does not confirm that assertion.

In other words, whatever steps one may take to make the mechanism work efficiently and smoothly, over-return from lowers seems to be simply a fact of life, and a solution to the problem, at least with keyhead steels, has not been found. But if a player accepts it, it can easily be lived with.

If anyone can refute what I've said, and testify to an approach to design or adjustment that in fact eliminates over-return, I'd be glad to learn that I'm wrong. Smile


Brint,

You analyzed the problem well......Return Compensators completely solves this problem. I suggest putting one whenever you raise and lower the same string.

Paul
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Paul Sutherland

 

From:
Placerville, California
Post  Posted 10 Jul 2011 5:31 pm    
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Can "return compensators" be retro fitted to any guitar, or just certain guitars? Where does one get them, etc.?
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Tony Rankin


From:
Florida
Post  Posted 15 Jul 2011 8:37 am    
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Paul Sutherland,

If your guitar is an all-pull (or Zum Hybrid) it is possible to add return compensators, if you can add a cross-shaft capable of being locked into position, bellcranks, pull rods, nylon tuning nuts, rubber O-rings and you have an open lower hole on the changer.

I did this to my Show Pro after ordering the parts from Jeff Surratt. I also did it to an Emmons LeGrande III that I used to own, after getting the parts from Emmons. My Zum Hybrids have them from the factory.

The first guitar I owned which was equipped with them was a Franklin. After playing the Franklin, and getting used to having them, I was never comfortable without them. I apparently became "sensitive" to return issues. I love having them!
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John Billings


From:
Ohio, USA
Post  Posted 15 Jul 2011 12:59 pm    
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"This has to be done with care so the rollers don't go flying."

Silly little addendum here Bent, but when I remove the rollers and the shaft, I put a piece of masking tape across the top. Haven't had them "go flying" yet.
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