Samsung tv LN40B530p7fxza sound Volume stuck on Max.

As a repair man I always hated that--had to disconnect the speakers and use a scope.

Most likely reason is the volume up control---a micro switch beneath the manual button on the set is bad.

These are momentary switches--only supposed to work when touched/pushed---they will feel good but have failed and are making contact all the time instead of just when pushed.

Only way to prove or disprove this is get at the keyboard and in your case locate (they can with set off be checked for resistance--should be no reading) is locate that volume up switch and unsolder it.

If problem is gone (your ears feel better) you have two choices : live with the switch removed and operate for that function with the remote.

Usually they only sell the complete circuit board with all the buttons for a set.

I would if could control volume just live with it gone.

Let me know if questions.