alpine cde102 head unit

I have a 2004 Honda Civic (5 speed). My brother (who is not an auto mechanic in any way) installed this stereo back in May. It stopped working in July randomly. Won't turn on, won't do anything. I've changed the fuse already, reset the head unit as well. Best Buy says it may just be a loose...

I just got this new radio...Alpine CDE-102. I hooked it up and it sounded sick for a couple of days. Now i got a 3 12's only pushing 500 watts...but i think i rattled something loose. Im getting all bass from the trunk but no sound from my car speakers. And now when after playing around with all...