[66 Buick Special]

If you are worried about the stereo, disconnect it at its power source for the time being.

If your underhood fuses are good you might start looking for a short in your ignition positive wire. Also, when it comes to fuses and relays I swap the ones out of the system I'm concerned with even if they "look" good.
Usually you can find another fuse of the same size in a non critical system and steal it temporarily.

Greg