Anonymous posted an answer for this Alpine CDM-7854:
"check the in-line fuse behind the radio"
Anonymous posted an answer for this Sony Xplod XM-554ZR Car Audio Amplifier:
"try disconecting ur battary for 2 min and try it again"
Anonymous posted an answer for this Volfenhag ZX-7180 Car Audio Amplifier:
"disconect ur battary and wait 2 min. if that doesnt work then 1 wire could be grounding..."