PDA

View Full Version : Intonation Problems



Uncle Mac
Dec-05-2008, 11:16pm
My first post here - I hope somebody can help.

I am relatively new to the mandolin, although I have been playing the guitar and the banjo for many years. I have an approximately 5 year old Breedlove KF Quartz that I bought used a few months ago. I love the instrument, but it seems to have intonation problems on the G string - generally sounding sharp from about two frets up, although I'm not having this problem on any of the other strings.

It looks to me like one of the metal posts on the adjustable bridge (the one on the g string side) may be bent, causing the top of the bridge to slope toward the fingerboard. Is this a common problem for adjustable bridges? If the post IS bent, how would I know? If I have a bent post, do I need to buy an entirely new bridge, or is there a less expensive fix.

Any insight you can offer would be appreciated. I think I'll try to get a picture of the bridge and post it up here.

Uncle Mac
Dec-05-2008, 11:32pm
Sorry. I thought uploading pics would be a good deal easier than it seems to be. So no pics. I could make some kind of facebook thing if necessary, I guess.

Mike Bromley
Dec-06-2008, 4:04am
If the post IS bent, that implies that the instrument may have taken a considerable impact at some point.

If it is misaligned and leaning, disassembling the bridge when the strings are off and reinserting the post into the bridge base may be an option. If it is bent, rotating it 90 degrees might help, if that doesn't cause it to bind in the bridge saddle.

On the other hand, if the nut grooves are crowned, the intonation will be thrown off as well.

Ivan Kelsall
Dec-06-2008, 4:25am
Hi - Do all the other strings sound ok apart from the G strings ?.Certainly,with your Mandolin being a Breedlove,i wouldn't have thought of any fret problems,so your 'bridge theory' could be it.
If you can't figure out how to post a pic. on here & also if you think that it's worth doing so,send me a personal message with your e-mail address.I will in turn e-mail you & then you can e-mail me the pic.(s) for me to add on here on your behalf. In the mean time,slacken your strings off
until you can move your bridge fairly freely & make any adjustment that you can to it's 'uprightness'
(is that a real word ??). If you can get the bridge in a perfectly 'vertical' position without any leaning forward or backward,tune up your G strings & check them again. If that fails, slacken the strings all the way off & remove the bridge. Take the bridge saddle off & check that the 2 screw threads aren't bent at all. If the one that you suspect of being slightly bent forward IS bent forward,you should be able to bend it back carefully. To do that ,you'll need to use a vice (vise)
to hold the base firmly.I would then,very carefully,use a small pair of pliers to ease the screw back to it's proper upright position. The screws are very small diameter & should bend easily with firm,but gentle pressure. I have done this in the past on an arch-top Jazz Guitar & it's easily done - just take it slowly & think before you do anything.
If you remove the bridge &then consider buying a new one - that's a whole new ball game. It's something that i've done,only once, but i'm awaiting a new bridge for one of my Mandolins
so i'll have to do it again. It's again, easy enough if you take your time & if you stick around Mandolins for long,you'll be doing it a few times as well maybe. Frank Ford's site "Frets.com" is the place to go for Mandolin bridge fittting instructions. Follow what Frank does & you'll be fine - again,
as i said,take your time & think things through before doing them,
Saska

Mattg
Dec-07-2008, 2:33pm
Could be two different problems. I agree with Mike B about the bent post, it sends up a red flag for sure. The bent post may not be as much of a problems as it would if it were loose. It's worth checking. If the post is bent or loose, it can be repaired and would be worth it if you feel like the foot of the bridge is fitted well to the mandolin top. For a bent post, I've found the same screw size at the hardware store and cut it down to size. For a loose post hole, I've put some epoxy down the hole and put the post back in while the glue drys. If you want a new bridge all together, look at the Cumberland Acoustic bridge. They are very nice and worth the money.

I have never gotten all strings on a mandolin to intonate perfectly. Perhaps someone with more skills can but I've tried. Who's to say that the predefined stagger spacing on a bridge will work for your particular strings? I work at the intonation until a happy medium is found.

Uncle Mac
Dec-09-2008, 3:20pm
Thanks guys.

It's definitely a bent post, although now that I have the bridge off and have had a chance to look at the thing carefully, it looks almost like the post was drilled into the bridge at a bad angle and then never corrected. I can't decide whether to try to bend it to the upright position or just put it back on and forget about it - it's not like I play that well anyway.

I have taken it by two guitar stores - neither wants to touch it. I don't own a table vise myself, so I'll probably have to use my neighbor's.

I'm very reluctant to try a new bridge - I have a bad track record of sinking money into instruments that I never get back out of them again and the idea of sanding and fitting the bridge does not appeal.

Uncle Mac
Dec-09-2008, 3:31pm
The consensus among everyone who's looked at it is that trying to pull the pin back up straight is going to shatter the bridge. So I think I'll just put it back on and try to live with it until I've found a local luthier who will shape a new bridge without charging me $50 to do it. I've got about 900 in the mandolin and I really like it, but I'm sick of sinking money into repairs on instruments that I then turn around and sell at a loss when I can't get them to sound right. ~:>

Ivan Kelsall
Dec-10-2008, 3:32am
I've straightened up a bend bridge screw that was fitted to an old archtop Jazz Guitar that i had for a while with no problem. As long as the base of the bridge is clamped firmly in a vise,the vise will take all the force that's transmitted thro.the wood. The screws are so thin,the biggest danger is breaking of them.
You could try just angling the bridge to bring back the 'forward leaning' bit back into line. It'll be a bit of a compromise,but it could give you better tuning across the board,
Saska

lenf12
Dec-10-2008, 2:54pm
Take a look at the base of the bridge (the part that contacts the top of the mandolin). Is the hole that holds the bent screw drilled all the way through the base? The screws often have an allen wrench hole in them. I think the smallest allen wrench 0.050" (iirc) is the one that fits the hole in the screw. Even if it doesn't have this hole, perhaps you can remove the screw with pliers, fill the hole with wood putty or a saw dust/glue mixture and then redrill and tap a straight hole when the filler dries. If the screw is bent, a replacement should be readily available for very cheap $ from Stu-Mac, LMI, etc. Also, have you contacted Breedlove for the cost of a replacement bridge (foot with screws only since the saddle seems to be OK)?? It may be cheaper than you think (especially for an owner) and may fit perfectly without much work. Just a thought.

Len B.
Clearwater, FL

mandroid
Dec-10-2008, 7:58pm
along the same lines...
Screw-stud bent?, tried that pool cue test?,
or is the drilled and threaded hole in the bridge base put in a little off?

if a new instrument Mr Breedlove and Co. should cover the work thru his dealer .