Adjusting the Truss Rod on a 1974 D-28
Just purchased 1974 Martin D-28 serial #335191. Want to adjust truss rod but there is no hole to insert wrench. How do I adjust it?
You should be able to find a hole which fits a 5 millimeter hex key in the brace under the fingerboard.
It might be best to take it to a qualified luthier, considering the age of the guitar.