I don't beleieve the MA6500 uses LED's so it may be burned out bulbs which can be a challenge to change. Order a service maual and some bulbs from Mcintosh and you can do it your self if you are comfortable with a soldering iron. Also check with Audio Classics if they have a LED kit for this model. If they are all out I would say power supply or fuse.
If they are LED and if they are all out same story PS or fuse. Contact McIntosh Tech Support and they can tell you if there is a seperate fuse.
