# Octaves, Zouks, Citterns, Tenors and Electrics > CBOM >  I need some advice!

## Ironhead

I recently purchased a Trinity College TM-325 octave mandolin. I have a buzz on the third string(D strings)when fretted. I tried to put a bit of relief in the neck by adjusting the truss rod, but loosening (turning left) or tightening the truss rod appears to make ZERO difference in the action. I capoed at the first fret and depressed the 21st fret and a credit card placed beneath the string at the 7th fret rubs the fret and string firmly, so much so that it is tight to squeeze between. Since the bridge is of the non-adjustable variety I am wondering if any of you knowledgeable members may have an idea how to raise the action. Is there an adjustable bridge I can purchase for a Trinity College octave mandolin? Any help would be greatly appreciated. The instrument has a really nice tone and sustain but the buzzing is killing my enjoyment. Thanks!!

----------


## foldedpath

Before you do anything else, you might try a string change. That's always the first thing I'd do anyway because who knows how long the factory strings have been sitting on the instrument. It's possible that you might fix the problem with a slightly higher string gauge, but I'm not conversant with 20.5" scale OMs (mine is 22") so maybe someone else here can recommend a set of strings or individual gauges to try.

There may be other issues with this instrument, but that's what I'd try first because it's cheap and the factory strings are probably shot anyway. The next step would be sending it to a luthier for a setup and any other issues that need addressing, like a possible high fret.

----------


## Ironhead

Thanks foldedpath. I put J72's on as soon as I purchased it.Good thinking though!

----------


## Ray(T)

To raise the action on a fixed bridge mandolin, you usually only need to add a thin shim beneath the saddle - ideally hardwood or possibly hard plastic will do - but the Trinity College doesn’t have the usual straight saddle so it might not be that simple.

It sounds like you might have a high fret(s). Take a short metal straight-edge and go through each of the suspect frets and see if the straight-edge “rocks” on any of them. You could have a high fret or you could have a loose fret. Ultimately, it may be a case of “Get the to a luthier” for a fret dress/level.

----------

Ironhead, 

Joe Dodson

----------


## John Kelly

Ray's advice on testing for a high (or low) fret is one of the first things I'd do.  Remember that you want the straight edge just long enough to span only three frets at a time so that you can accurately find the rogue fret.  I have a couple of devices I made in my workshop, one from aluminium and the other acrylic, which are basically flat scalene triangles with the three sides of different lengths, to cover the various fret spacings up the neck.  When I made them I made one for guitar and octaves, etc, and one for mandolin (smaller on all three sides to accomodate the shorter scale).  I made sure they had very flat edges by finishing them off on a surface plate with very fine wet-and-dry paper and micromesh.  A suitable sheet of plate glass will stand in for the surface plate;  I was just lucky to have access to one from an engineering friend.

----------

Ironhead

----------


## Ironhead

Thanks Ray and John. I checked the neck for a high fret and there are none! Neck is straight but action needs to be higher. Since the truss rod appears to do absolutely nothing toward this end I guess a replacement bridge is about all I can think of. I don't know of any though so I'm at a bit of a loss.

----------


## MikeEdgerton

You might want to take a look at *this* article from Frank Ford's www.frets.com as well as *this* one from the same source. I probably should have sent you to the second one first.

----------

Ironhead

----------


## Ray(T)

> Thanks Ray and John. I checked the neck for a high fret and there are none! Neck is straight but action needs to be higher. Since the truss rod appears to do absolutely nothing toward this end I guess a replacement bridge is about all I can think of. I don't know of any though so I'm at a bit of a loss.


Its a common fallacy but the truss rod hasnt anything to do with adjusting the action. The action is set purely by the height of the nut and saddle. The truss rod adjusts the amount of relief (neck bow) a neck has. Most people opt for perfectly straight necks on mandolins and a slight bow on guitars. OMs and mandolas fall somewhere in the middle. You need to sort out the action first and then dial in a sufficient amount of relief. Probably a job for a luthier if you dont know what youre doing.

Ive never seen one of your OMs in the flesh so its a bit difficult to know whether a shim beneath the saddle is possible. It should be but it depends upon the depth of the saddle slot. If its too shallow, the saddle wont be stable and could tip over. Having a new saddle made isnt a big deal for someone who knows what theyre doing.

----------

Ironhead, 

Jim Garber

----------


## Ironhead

All good info! I should have phrased my terminology a bit differently. I was making the point that the truss rod does nothing to change forward relief in neck nor straighten or flatten. No relief can lead to string buzz on the first few frets as I'm certain you'll agree, as the frets are closer to the string without relief. I know how to check for neck relief but shimming a saddle would be a bit beyond my skill level.

----------


## Ironhead

Thanks Mike! I've seen that excellent link for troubleshooting buzzes and rattles before but forgot about it. Thanks for reminding me and providing the links.

----------


## rcc56

Unless something has changed that I am not aware of, while the bridge on a TM-325 is non-adjustable, neither is it a fixed bridge.
A wooden shim can be inserted underneath the bridge to raise the action.  Ebony is best, but any hardwood would work.
We sometimes use this technique to raise non-adjustable bridges on old instruments, including 1910's Gibsons. 

Or an adjustable bridge can be made for the instrument.  If there is enough arch in the top and the string spacing at the bridge is not too wide, a full contact Cumberland Acoustics mandola bridge could probably be made to work.  If you ordered direct from CA, they might be able to run you one that has a flatter base than their usual spec so that it could be fitted without removing too much wood from the base.  Or, if they don't want the job, a number of us [including myself] could make you an adjustable bridge from scratch if necessary.

Whoever makes the bridge, it would be best to furnish the maker with an accurate tracing of your current bridge.  It would enable him to get the right amount of arch on the bottom of the base so it would require a minimum of fitting to match the top on your instrument.

Bear in mind that any replacement bridge will have to be fitted to the top and have the saddle slotted by a competent repairman.  If there's not a fretted instrument repairman near you who is capable of fitting it, a violin repairman would be able to handle the job.

----------


## Jim Garber

> It’s a common fallacy but the truss rod hasn’t anything to do with adjusting the action.


I was waiting for someone to mention this. Thanks, Ray!




> Unless something has changed that I am not aware of, while the bridge on a TM-325 is non-adjustable, neither is it a fixed bridge.
> A wooden shim can be inserted underneath the bridge to raise the action.  Ebony is best, but any hardwood would work.
> We sometimes use this technique to raise non-adjustable bridges on old instruments, including 1910's Gibsons.


Sometimes you may only need a very thin shim. I have a roll of iron-on hardwood veneer and I have used a sliver of that as a shim. If you only need a layer or two of it it will follow the contour of the top and you may just need to trim it to the size of the base of the bridge. Then I use a black Sharpie to match the ebony of the original bridge unless, of course, it is some other lighter wood. This works very nice for me for a quick non-pro but functional fix. I got a roll of this stuff years ago from Home Depot. I think this may be the same stuff or similar: https://www.homedepot.com/p/PureEdge...2158/310449285

----------


## Ironhead

VERY helpful information. Thanks rcc56! Those are some great sounding solutions. What if I sent the bridge from the Octave mandolin to you and you copied it and added a bit of height. Then you could slot it too? Is that a possibility?

----------


## rcc56

PM sent.

----------

