i recently bought an omi dobro: a 1971 in decent shape. i liked it but i knew someone had messed with it because it had a bunch of extra dot inlays up the neck making the fretboard look more like a domino in places.
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374641559.jpg
no matter it's still a cool dobro. but the more i played it the more i became aware the sound wasn't right. even with a set of 13s the instrument sounded tinny, whiny, and shrill on certain notes when i played slide. now i have never worked on a dobro before and my experience of working on guitars is limited to poking around occasionally inside strats and acoustics but i am no luthier. i want to pass on what i learned because i am sure it will be helpful to someone out there who wants to avoid an expensive repair bill.
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374698800.jpg
the first thing i found when i removed the dobro's cover plate and loosened the screw in the middle of the spider bridge was that the cone wouldn't budge!!!
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374641562.jpg
i knew the cone was supposed to pop straight out and fast concluded that a prior act of sacrilege had been committed. person or persons unknown had glued the cone to the body!!!!! i did my best to pry it loose with a razor blade, knife, scraper and chisel but it was glued so tight it got bent and misshapen as i wrestled with it. once it was loose i pulled so much glue out of the sound hole it was ridiculous. the stuff was coming outta there like spaghetti.
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374641567.jpg
i am guessing someone glued the cone because it rattled - rather than carefully adjusting the cone and spider to get the perfect tension and thus tone.
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374641563.jpg
i ordered a quarterman from janet davis music in arkansas. i decided on a 10 1/2 inch cone as opposed to the 10 9/16 inch ones beard make as the omi's originally had 10 1/2 inch cones. so i thought it would drop right in. in fact i spent the best part of 2 days scraping, filing, sanding and chiseling to get that cone in there. the best tool of everything i tried was a simple paint scraper. i had to file the cone itself and the guitar to get it to fit properly. but when it finally slid in it felt right.
http://pic90.picturetrail.com/VOL2220/12674497/22545971/374641564.jpg