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1975 Conn F-2112
Bridge Pulled Off, Bad Prior Repair (Block of wood glued inside with subfloor adhesive), top wood delaminated and contaminated with foreign material.
This is the kind of repair that probably challenges me the most. Although I realize that friends always have good hearts and try to do right for their friends, with guitars it doesn't always work out. Along comes me, who has to undo the good intentions so that I can make the instrument playable. Undoing a bad repair is probably one of the biggest challenges I ever face. First I didn't think I would be able to remove the block without taking the back off the guitar. The guitar was not worth the time or money it would have taken to do this. So I used heat to remove the upward bowing. Applying the heat to a localized area is the biggest challenge because applying it to a large area might loosen the inside bracing. So you can see how I accomplished this in the photos below. After using heat and pressure to remove the hump where the bridge had pulled off, I decided to just give it a try at removing that inner block of wood. I was able to remove it by using an acetone solvent. Then I worked for a long time to get all the subfloor adhesive removed from the wood. Once off, I proceeded first to re-laminate the top wood so that the glue would hold the bridge back in place.  Follow the pictures below to see how this repair progressed.
BEFORE PHOTOS:
 1970's Conn F-2112 - Bridge torn off, and bellying (Below) 

01 Initial Conn F-2112 Inspection:

Here you can see a block of wood has been glued in place under the soundboard. This block of wood is approximately 2" x 3" x 3/8" thick. Bridge-pin holes have been drilled through it. This is the worst kind of repair to encounter; one that has been done badly and that must subsequently be undone to do correctly. The glue used was sub-floor adhesive--lucky for me, easier to remove than wood glue!

Here you can see just how badly the wood is delaminated. What you cannot see very well in this photo is the amount of subfloor glue that is filling every crack, crevise, and split. That had to all be dug out using a pick.

 

 

The bridge, shown above, has glue and pieces of wood on it. But no problem. This can be removed on a belt sander.

 

 
 BELOW BEGINS THE REPAIR (STARTED ON 4/9/2012) 

 

PIECES OF THIN MAHOGANY CUT AS REINFORCEMENT FOR UNDERSIDE OF BRIDGE. THE BRIDGE AREA, AS CAN BE SEEN FAR ABOVE, WAS IN SUCH BAD CONDITION THAT IT WOULD NOT HAVE SUPPORTED ANY PULL OF STRING TENSION. THESE ARE INTENDED TO PROVIDE NEW WOOD AGAINST WHICH STRINGS CAN PULL AND NOT BOW UP THE TOP OF THE GUITAR.

TOP (FIRST PIECE) GLUED IN AND DRYING UNDER CLAMP PRESSURE. 

 

SECOND PIECE OF MAHOGANY GLUED IN PLACE AND DRYING.

THIRD PIECE OF MAHOGANY NOW GLUED IN PLACE AND DRYING. 

 

THE BRIDGE (AS YOU SAW FAR ABOVE, WAS A MESS. ALL WOOD REMOVED FROM THE BOTTOM, AND THE TOP HOLES WERE FILLED WITH A PROPRIETARY METHOD, AND THE BRIDGE WAS STRIPPED, RE-EBONIZED, AND LEVELLED.

AFTER LEVELLING THE BRIDGE, THE REINFORCED MOUNTING SURFACE ON THE SOUNDBOARD HAD TO BE LEVELLED TO ACCEPT THE NICE FLAT BRIDGE. ONCE LEVELLED, THE HEIGHT OF THE BRIDGE ATOP THE SOUNDBOARD WAS AT OPTIMAL HEIGHT--JUST ABOUT 1/16" FROM TOUCHING A STRAIGHT EDGE PLACED ON THE FRETBOARD. 

 

SHOWN HERE, THE FRETBOARD HAS BEEN GLUED BACK IN PLACE, AND THE BRIDGEPIN HOLES RE-DRILLED, THEN THE SADDLE AND BRIDGEPINS INSTALLED TO CHECK FOR FIT.  STRING INSTALLATION WAS NEXT, AND IS NOT SHOWN HERE, BECAUSE THAT WAS THE FINAL STEP.

 
 BELOW -- REPAIR COMPLETED (4/21/2012) 

 

FINISHED ON 4/21/2012. YOU MAY NOTICE THE LIGHT G STRING MISSING. IT BROKE UPON INSTALLATION. I WILL BUY ANOTHER AND INSTALL IT BEFORE GIVING THIS GUITAR TO THE CUSTOMER (JEFF).

ACTION IS LOW AS IS SHOWN BY THIS PHOTO. IN FACT ONE FRET WAS RAISED (HUMIDITY ISSUE), CAUSING A BUZZ, WHICH I WAS ABLE TO REMEDY BY TAPPING THE FRET BACK INTO PLACE. 

 

THIS F-2112 IS A GREAT GUITAR. I WAS DISCOURAGED WHEN I FIRST SAW THE BLOCK OF WOOD INSIDE, ASSUMING THE WORST. HOWEVER, IT HAS PROVEN TO BE HEALED QUITE WELL...MUCH LIKE HIP REPLACEMENT SURGERY -- IT SOUNDS AS GOOD AS NEW, AND IS BETTER THAN IT'S BEEN IN A LONG TIME.