There are several reputable music stores in the Knoxville area that can capably repair musical instruments for a fair price. No matter where you live in K-town, odds are there's a competent repair facility in your area.
West Haven/Lonsdale - Lunsford's Musical Instruments - 3606 Western Avenue; 37921 (865) 523-0276 - Specializing in school and university band instruments, Lunsford's is conveniently located less than ten minutes from the UT campus. They also service orchestra and electric stringed instruments in their well-stocked repair shop. Hours - 9-6 M-F; 10-5 Sat; Closed Sun. (http://www.lunsfords.com/).
North Knoxville/Fountain City - Broadway Sound - 2830 North Broadway; 37917 (865) 637-1644 - Known as "Lynn's Guitars" for years until the mid-80s, Broadway Sound specializes in mainly rock and country instruments. Their repair facility also services amplifiers, PAs and other electronic music gear. Hours - 10-5:3 M-Sat. (broadwaysound.net/).
North Knoxville/Powell - Ciderville Music Store - 2836 Clinton Highway; Powell, TN 37849 (865) 945-3595 - A shop every bit as colorful as it's history, Ciderville Music was home to many famous bluegrass and country music icons of East Tennessee, including the infamous radio host, retailer, and politician Cas Walker. Ciderville has some very knowledgeable repair and service personnel who not only know guitars and basses, but also are adept at mandolin, banjo, fiddle, and dulcimer repair as well. Hours - 9-6 M-Sat. (http://www.cidervillemusicshop.com/about.html).
West Knoxville/Farragut - Guitar Center - 8917 Towne & Country Circle; 37923 (865) 670-1022 - Located less than a half mile from Exit 378 on I-40 (Cedar Bluff Road), Guitar Center has several competent repair technicians who also repair amps and accessories as well. They also keep the longest business hours of any music store in town: 10-9 M-F; 10-8 Sat; 12-6 Sun. (http://gc.guitarcenter.com/locations/store.cfm?store=721&source=4WWRWXGT).
Riks Guitars and Sound - 8426 Kingston Pike; 37919 (865) 651-9590 - Easily to find on Kingston Pike and accessible from I-40 (Exit 379/Gallaher View Road), owner Rik Asher is also a guitar tech himself, along with his service man J.D. Brown. Hours - 10-9 M-Sat. (www.riksguitars.com/).
Pick 'n' Grin - 106 Gore Street; 37919 (865) 588-5361 - Just off Kingston Pike in the Sutherland Avenue area, Pick n' Grin specializes in bluegrass stringed instruments, but also has a world-class electronic instrument repair facility, too (with some of the most reasonable rates in the city). Hours - 10-7 M-Th; 10-6 Fri-Sat. (http://www.pickngrin.com/).