1986 Honda Prelude stereo install

To me it sounds like you've got an internal short in your headunit.  Replace the fuse, and try testing it at the battery to see if it powers up.  Just twist the red and yellow together, and touch positive, while touching black to ground.  Ensure your speaker leads are not touching or connected to anything.  If the fuse blows under these conditions, you know the unit itself is the problem.  If not, it's in your wiring.My ex once told me I have a perfect face for radio.