Truss Rod Adjustment at Heel

With an angled hex wrench (shaped like in L), unless Ernie Ball is using some strange rod nut,like Gibson.

 

Looks like a spoke-wheel truss rod nut. If so find something like an hex key that will fit into the small holes around the perimeter of the spoke wheel and use it to rotate the wheel. Rotate it clockwise (while viewing from the body towards the nut) to flatten the neck, counterclockwise to add more relief.

 

http://www.music-man.com/faq/guitars/

 

Nah, there's no magic tool required. Anything sturdy that will fit in there without snapping off (like the tip of my Swiss Army knife pick did once) - don't remove the strings, just push them aside and do 1/4 turns at a time (eg, do a 1/4 turn, check it the next morning after settling).

 

If you insert the hex key (or whatever) too far, it just wedges between the spoke wheel and the body and won't turn. You were on the right track in the first place since you were able to turn the wheel. If turning the wheel is making no difference at all then (assuming you are tightening it) there is another problem, like stripped threads on the wheel or a broken truss rod.

 

They have the same on stingrays (maybe most MM basses do, I'm not sure) and it's pretty easy, but like the other guys said, you do need something pretty sturdy.

You probably already knew this, but for tightening the truss rod you need to turn it clockwise, looking towards the headstock.

 

I didn't know Timothy Leary even played bass, let alone owned Markbass gear!

 

I didn't know that either!

 

Yeah, use standardised 1/8 - 1/4 turns. I've found I don't need to turn it much at all, but when I adjust it's only a minor adjustment anyway.

If the bass is vertical and upright with the body facing away from you, you would be turning the spoke wheel to your left.

I always modify the truss by placing it face up on my lap with the headstock on my left (similar to normal playing position), insert a hex key (I've found a 1/8 one works best) and turn the wheel away from me, to tighten the neck.

 

Here is a video from Drew at MM showing the truss adjustment .