home stereo/shelf unit repair

[CHAOS]

I’ve got a slightly weird issue with my shelf unit stereo that I’d possibly like you to take a look at. Its all dependent upon cost of course. I’ve got a sony shelf stereo (3 CD changer, tape decks, 460 watts, game input and video out) which is barely used… but everytime I turn the unit on after its been unplugged for a while it works fine… then after an extended amount of time using one setting… for instance listening to a cd… without touching the unit.. it basically locks … none of the buttons on the face work… I cant turn it off, cant turn the volume down, or switch modes… the only way to get it to shut off is to unplug the unit… and when I plug it right back in… nothing lights up besides the standby light… and when you hit the power button it shuts off like it would when the unit is normally turned on but nothing functions or lights up… if you guys have any insight into what the issue may be here id love to hear about it... im also wondering if anyone knows of a place that could possibly fix said issue...