I have an alpine mrv=t303..there is output,,where the rca's wire to circuit board ,,but it makes a buzzing noise like its not grounding on the board.nothing is burnt up on the board and thr rca inputs have been removed to troubleshoot.when i hook up wires to the board where the rca jacks get soldered in it makes a loud buzzing noise.Between my brother and i we have almost 20 years of combined experience working on car audio electronics,,,,please help us.....btw www.fixya.com is the best website for troubleshhoting,,,i firmly believe that....

Try different speakers and wires first.

remove the rca wires and the speaker output wires and just leave the 12volt power/ remote/ and ground connected. turn on the radio and see if the light goes off. if it does then one of your speaker or rca wires are shorted, plug in one at a time and see which one gets you the red protect light, then find the short for that speaker/rca wire. if the red light turns on with only the 12volts/remote/ground, then the short is in the amp.

I honestly don't have a solid answer for you. I can say check your fuses. Check your battery to amp wire. And also check your ground. Make sure the fuse on your amp is also not blown

There should be an amp input level control somewhere close to the rca inputs...does this have any effect?

I suppose you checked all the usual suspects? Fuse, Ground, and Remote turn on?
Now if memory serves me isn't that an amp that has a digital display on the top? If so you have to scroll thru the menu items and see if it is on low pass or even off? The gains are tricky because they get louder with less dbs. but check the outputs.
if all else fails it's probalby bad.

Alpine is just a better brand in general. I have the older MRV-1507, sounds GREAT, i have had friends who has had the Explode line, but it was always a temporary system until they got something better, like the alpine or kenwood.

If it indicates that you have an open shield ground, read through the following page. It will show you how to test the shield ground connection of your head unit..

Temporary RCA Shield Repair

The MRV-1507 is a two channel amplifier, below I've pasted important info from the manual:

Battery Lead (Sold Separately)
Be sure to add a 80 amp fuse as close as possible
to the battery’s positive (+) terminal. This fuse will
protect your vehicle’s electrical system in case of a
short circuit. If you need to extend this lead, the wire
gauge should be AWG8 or larger.
MRV-1507 ... 80A amp fuse

Power Output: RMS Continuous Power (at 12.0V, 20 Hz to 20
kHz)
MRV-1507
Per channel into 4 ohms ......................... 150W, 0.08% THD
Per channel into 2 ohms .......................... 300W, 0.3% THD
Bridged into 4 ohms ................................ 600W, 0.3% THD

You can find a manual for this amp here:
http://www.alpine-usa.com/US-en/support/support_search.php?modelname=mrv-1507

disconnect all power (15min) try again with different speaker to see if sub is dammage.

power wire from fuse block goes to "the 1 that says power"...remote is used to have your device turn another device on...like a cd changer