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The Guitar Medic

By Appointment
Repair and Restoration
1898 Mandolin
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Conn F-100 6-string Acoustic Guitar - Neck Reset
This Conn guitar is one of the lower-end Conn acoustic instruments made in the 70's. But like with any Conn guitar, it is worthwhile to have (when playable) because they are great sounding guitars--reminding me of the Yamaha red-labelled guitars of the same era.
This one came to me from a gentleman in New York, who purchased it on the web site. It was not really playable upon receipt. It seemed that over the years, things had moved, and the action was so high that all attempts by the owner to bring down the action were fruitless. He sent it to me, and asked if anything could be done. The label shown at right is for cosmetic purposes only and is not the label for this actual guitar.  It is representative of the type of label that was installed on these models. The actual label is missing.
When I get a guitar in my shop, that has high action, the first thing I look for is 'the cause'. Sometimes it's because bracing has come detached in the soundboard (just under the bridge) and allowed the top to raise or "bulge". Sometimes it is a shifting of the neck and heel block--indicated by a crack alongside the fretboard on the body. Other times it might be simply a neck set from the factory that was already questionable, and only got worse with time. Or it could be due to humidity problems.  Whatever the reason, I first eliminate these causes before I would promote a neck re-set.
Neck resets are a lot of labor, and frankly I don't like doing them. The payback is just about break-even for the grief.  But I still do them.

Unfortunately I have no photos of how high the action was.


Here is an enlarged view showing the string offset toward the bass side. When strings are shifted this direction, the result it possibly pushing the low E string off the bass side of the fretboard when making chords.

Here you can see a place in the heel where it appears there was a crack that was repaired. Later, after removal of the neck, it was found that the guitar had a former neck set.


12/21/2015  Strings, bridge pins, saddle removed.

12/21/2015  Checking action setting prior to beginning work.

12/21/2015  Action check should be slightly to 1/8" above the bridge, to ensure adequate saddle height to adjust action low at the fretboard.

12/21/2015 In a dovetail joint, the dovetail cavity is typically located under the 15th fret. So removing that fret (heat and remove) allows drilling 3/32" holes in which to insert steam to loosen the joint.

12/21/2015  Before the steam is applied, the fretboard glue at the body must be loosed to allow removal of the fretboard. I use a small portable iron to heat the area and the putty knife before beginning.

12/21/2015  Forgot to mention that I first strap down the guitar. I use standard ratcheting straps, but I place a large piece of cork under the ratchet mechanism to protect the guitar.

12/21/2015  Some time back, I bought this hotplate to heat the water in the pressure cooker.

12/21/2015  Here you can see my pressure cooker. I have attached some 1200 lb pressure hose (purchased at an auto parts store) to the pressure valve. A small worm-drive clamp holds it in place.

12/21/2015  I made a handle out of a bracket, and inserted a basketball needle, then secured it all with a worm-drive clamp.

12/30/2015  After steaming the neck, the area separated where the appearance of a "repair" was.

12/30/2015  Upon examination, it was obvious that the neck had been re-set before, and this was in fact an ebony shim. Good thought, but done poorly, and the neck set was apparently not successful.

12/30/2015  Here, I have removed the black ebony wood, and finished the heel interface at the proper angle to achieve the height I need. I have created a spreadsheet with some formulas that calculate the angle based on measurements that I take and enter.

12/30/2015  Here I have clamped on a mahogany shim (same material as the neck).

1/1/2016  After doing some other tweaks on the angle and filing away high spots, the neck is glued, reinserted, shimmed and clamped for 4 hours minimum.

1/1/2016  Here you can see the neck after clamps are removed, Between the dovetail and the body, you can see a shim inserted on the near side.

1/1/2016  Here you can see the shim I inserted. I am undecided whether or not I want to stain it to match the neck or to leave it light to add a nice cosmetic touch.

1/1/2016  Laying a straight edge along the edge of the fretboard is a good way to check string alignment to the bridge. Laying it along the right edge, I then hold it tight, and look at the spacing (see next photo at right).

1/1/2016  Here you visually see the spacing is about 1/4" from the bridge pin hole.

1/1/2016  Same exersize on the left side.

1/1/2016  Here you visually see the spacing on the left side, again, is about 1/4" from the bridge pin hole.

1/1/2016  Now to check action. Laying a straight edge on the frets, it is extended down to the bridge. It should be flush to about 1/8" above the bridge.

1/1/2016  As you can see, the desired result has been achieved. The measurement needs to be taken in the middle and at both edges of the fretboard. Here I'm taking the measurement at the right edge.

1/1/2016  Here I'm measuring the height in the middle. I am mainly looking for consistent gap.

I spent several days making shims to shim the over-body portion of the fretboard to get a proper angle. Any time you change the angle of the neck, the fretboard will now need to be shimmed at the body, so that it doesn't have a large air gap under it, or so it doesn't have an OBVIOUS angle in it at the body. This has to be pretty much perfect.  See Picture below:




1/6/2016 In this photo you can see that I've begun sanding to level the shim.

1/6/2016 In this photo I've begun applying dust to fill the gap. I use a combination of wood glue and sawdust to fill the small gap. This photo taken on Jan 1, 2016.

1/7/2016  I made these cawls from rock maple. They were scraps from a guitar-building job, so they're plenty hard so as not to bend, but still provide the protection of wood-against-wood. I notched out the fret areas, so the pressure is on the rosewood. 


1/7/2016  Same view, different angle.

1/7/2016  Inside, beneath the body, I placed a block of oak. The oak also does not bend under pressure, and allows me to spread out the clamping force, so that the wood inside doesn't get drawn up or warped.


1/8/2016  Here I have begin filling in the joint to make it look better cosmetically. This is just cosmetics at this point. The neck is securely in place, so everything hereafter is cosmetic in nature..."just to make it look good". I got sick about this time, and took a few days off.

1/11/2016  Frets glued back in. Clamped to secure while glue dries. When reinstalling removed frets, wood glue is used to reinforce the slot.

1/11/2016  Side view of glued fret. Clamped to dry. After unclamping, frets needed levelling. I levelled them locally in this area only.

1/14/2016  I masked off the guitar so that only the repair area and bottom of neck are exposed. Then began spraying with Varathane Mahogany polyurethane.

1/15/2016  Several coats later, it is beginning to hide the repair. Still some finishing to do. Not all steps have been photographed.

 1/16/2016  Finished. With strings on, the action is about 1/8"--first try. Lots of saddle (perfect amount) protruding above the bridge. Room to adjust. After adjusting the truss rod to remove the concavity, the action dropped to about 3/32"--excellent.

1/16/2016 Finished. Showing action, but difficult to judge from a photo without a reference (a Quarter for example). I had no coins in my pocket. But the action is about 3/32" at this--the 12th fret.



1/16/2016 - Here you can see that there is plenty of saddle to allow lowering if needed. The saddle protrudes about 3/16" above the top of the bridge. It seems ideal. For now I am happy with the action, but may lower it at a future date. For now, I've adjusted the truss rod to get the neck nice and straight. I'll wait a day or so to see how straight it is, then make minor adjustments from there. For now it's pretty darned good.

May 5, 2016 - I gave this guitar to a teacher in a middle-school program in Frankfort, Indiana. The teacher devised a program wherein he integrates guitar lessons with teaching math. The program is called "Rockdogs".  He occasionally gives away one of his guitars (he has about 20--he bought them all and a few were donated) to a student who shows initiative, but whose parents cannot afford to buy one. The program has been highly successful, so this guitar went to a great cause.