It's possible that there is a bad ground, but most likely the problem is that you are drawing too much current through a small fuse (pop) or a thin wire (melt). You need to get the EQ powered via a FUSED line from the battery, with the fuse as close to the battery as possible, and use the under-dash wire that WAS powering the EQ as a signal input to turn the EQ on. This pic should help.

Most EQs have a four-wire plug:
-a RED power in (fused +12v from the battery)
-a BLACK chassis ground (close to the EQ itself)
-a YELLOW remote input (from the CD player or other signal in)
-a BLUE remote output (to the amps)

Oh, and I am not liable for any damages or injuries that may result from miswiring or mistakes.