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FDP Forum / All Other Fender Guitars and Instruments / Extra spring notches on KC Mustang bridge posts?



Mar 30th, 2018 08:28 AM   Edit   Profile  

I have a Fiesta Red KC Mustang. The vibrato action is very loose. I don't think there is enough spring tension to bring the strings back up to pitch after dropping down the bar.. The guitar goes instantly out of tune as soon as I touch the bar. The KC has one of those Fender Tun-O-matic clone bridges. My Classic Player HH Jag has that same bridge and scale length and it stays in tune better than any non-locking trem unit that I have ever played, so I am thinking the KC can be set up to stay in tune much better that it does currently. The trem action is much stiffer on my Jag, so I think that may be part of the solution, as well as possibly a shim. The Jag has an angled neck pocket, which also increases string tension somewhat. The tech that works on my guitars said there is an extra set of spring notches cut in my Mustang's bridge posts that he does not normally see in a Mustang. Moving the springs to this notch would increase the spring tension, but he said I might have difficulty changing strings because the cigar tube thingy would rotate back such that the string insert holes would rest at an inconvenient angle relative to the body. I am thinking that I could just simply push down on the vibrato bar with one hand and insert the strings in the holes with the other. Has anyone ever seen or utilized these extra notches in a KC or other MIJ Stang? If so, did it make it difficult to change strings?

(This message was last edited by Ricey at 10:29 AM, Mar 30th, 2018)

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UNpopular music

Mar 30th, 2018 09:22 AM   Edit   Profile  

The original Mustang tailpieces did have these 'extra' spring anchor notches; see pic below. I have a 1966 Mustang and they are there on the posts.

These were part of the design because if you went up to 12-ga strings, they were too stiff for the notches close to the bridge plate, and would pull the bar all the way to the pickguard.

Move the springs to the notches at the ends of the posts, and that floats the bar again.

The three notches also allow you to fine-tune (sort of) the angle of the bar based on your preferred string gauge.

The Mustang vibrato is a bit fiddly, but there are several things you can do to slick it up and make it play in tune. Lube on the vibrato pivot points, bridge saddles, and nut help immensely too.


(This message was last edited by Peegoo at 11:23 AM, Mar 30th, 2018)



Apr 1st, 2018 03:12 PM   Edit   Profile  

Great pic! So will moving the springs on my KC Stang to the ends of the post increase the back tension on the tailpiece, so that it will pull back to pitch more forcefully? Will it put the string holes in a bad position for changing strings?

(This message was last edited by Ricey at 05:13 PM, Apr 1st, 2018)

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Get ready for the

Buena Buena
Apr 1st, 2018 03:43 PM   Edit   Profile  

Yes, it will apply more spring force against the pull of the strings.

No, it will not put the strings' loading holes in a position that makes re-stringing difficult. That is physically impossible because the threaded studs that pass through the tailpiece plate prevent the tailpiece from over-rotating. In fact, if you look at that pic again, you'll see that the tailpiece bar is bottomed out anyway with the springs in the lowest (least tension) positions.

Keep in mind though--adding back pressure by moving the springs' anchor location toward the end of each stud will not only increase spring tension--it will also cause the vibrato bar to be higher (farther away from the face of the guitar) when the strings are tuned to pitch.

On the surface, the Mustang vibrato is a very simple design...and it is. But there are some tweaks that players (and 99% of techs) are unaware of.

If you think about these little notches as being similar to the spring claw in the back of a Stratocaster, it all becomes clear. The difference is the screws on a Strat's spring claw provide infinite adjustability of spring tension. On the Mustang, you get only three settings.

But not quite! Yu can cheat a bit and place each spring in a different notch. Some people will think this uneven tension is bad, but that is BS; the tailpiece bar is NOT going to twist out of shape, and the bar won't pop out of the tailpiece plate.

So for instance, let's say you have both springs in the middle notch, and you want more spring tension. So you move both springs to the end notches. And now you have too much tension. The solution is to move one of the springs (doesn't matter which) to the middle position. You've just reduced spring tension a bit.

The other thing to check is to make sure the bridge (where the string saddles are) is properly rocking in its little steel cups. If it's not, the guitar won't return to pitch after using the bar.

Each end of the bridge has little holes in it. At the bottom of each hole is an adjustable pointed set screw. You stick the long leg of a 1/16" hex wrench into the hole to engage the screw and adjust it.

These little screws do two things: they allow adjustment (up and down) of each end of the bridge to set string height, and they are pointed on the end to allow the bridge to pivot just a little bit when you use the vibrato bar.

To set up the bridge to pivot, do the following:

Set up the guitar for proper string height using the bridge height screws, and re-tune the guitar. Lean on the bar to cause all strings to drop in pitch about a half step. Release the bar, and the bridge should be about centered in its range of rocking motion.

Bottom line: the Mustang vibrato is similar to a Bigsby in that it's designed to create a bit of a wobble in pitch. It's not for doing dive bombs. Uses properly, with a good setup, the Mustang will stay in tune.




Apr 1st, 2018 04:24 PM   Edit   Profile  

Thanks for a very thorough and simple to understand explanation of the Mustang vibrato assembly. I have learned more from your posts than from all my other research combined!

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Get ready for the

Buena Buena
Apr 2nd, 2018 02:45 AM   Edit   Profile  

Cool, you're welcome.

Yet another thing you can do to fine-tune the balance of tension between the springs and the strings is to unscrew the studs several turns from the tailpiece bar.

This raises up the bar from the plate and gives the strings a bit more leverage to pull against the springs.

You need a minimum of four threads into the bar on both ends to keep things together, so you do have quite a bit of adjustability there.

Contributing Member

Get ready for the

Buena Buena
Apr 2nd, 2018 11:55 AM   Edit   Profile  

Please do me (and your tech) a favor; paste this thread into a text document and give it to your tech.

All of us learn from each others' experiences. Knowledge is power, and the more your tech knows about this stuff, the better the service to customers will be. It's money in the pocket--and happier customers!



FDP Forum / All Other Fender Guitars and Instruments / Extra spring notches on KC Mustang bridge posts?

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