Here's a great example of a cool acoustic guitar that Gibson only made for a couple of years: The Starburst. A peek at the inlays quickly reveals the source of it's name. This one came into the shop with the complaint that it buzzed and played out of tune. The guitar owner was confused because he had taken it to his buddy (who,invariably has been "playing for years") who had just set it up for him. Folks,if you take anything away from this,please understand,playing guitar for years doesn't make you a good guitar tech any more than driving a car for years makes you a good mechanic. For every good amateur tech in the world,there are dozens of well intentioned guys who know just enough to be dangerous.
Tilting saddle = bad intonation!
A quick inspection of the guitar revealed the biggest problem right away. The saddle was tilting forward. An ill fitting saddle can cause loss of volume and tone and when it tilts forward like this one does,the intonation goes out as well. To make matters worse,this guitar has an under saddle pickup.Having your saddle make questionable contact with the pickup is asking for all kind of string to string volume issues.The well meaning buddy had removed the original saddle and replaced it with a "better" one.
A new saddle and a good setup with fresh strings and this guy was back in action. A good fitting saddle is absolutely essential for good tone and doubly so on any guitar with an under saddle pickup! An excellent rule of thumb for good saddle fit is it's tight enough to stay put if you turn the unstrung guitar upside down and its loose enough to pull out with your fingers.