Amp power/speaker pulses when speakers connected

[Roberam]

I have a 98 Mercury Sable and have recently upgraded several audio components:

I put in a Dual XDM7610 aftermarket head unit (new)

Then replaced the rear speakers with Boss CH6940 6x9's (new)

And now I'm trying to add a VISONIK V1802A amp to power the 6x9 rear speakers

-USED, bought off ebay, was supposed to be in working condition, but I wouldn't be stunned if this amp has a problem due to the conditions I have.

I used 4 gauge power and ground wires, mounted under passenger front seat.

Before installing the amp the head unit and rear speakers worked fine.

When I first installed the amp I got power (no sound), but seconds after it being on one of the rear speakers popped and smoked. I disconnected everything, re-connected and tried a test set of speakers to see if I could get it working. One of the speakers (both right and left connected) kind of pulses and jumps with no real audible sound, and I noticed the power led on the amp also pulses. When no speakers are connected to the amp the power light stays on steady, no pulsing. Also I have all of the settings turned down, but they were up when I blew the original set of speakers (not the test ones). I'm stumped as to what the problem is, but I am going to test it with a portable CD player tomorrow to see if it is possibly a problem with my RCA cables or head unit connection. Just looking for some possible solutions to this problem if it is not the head unit/RCA cables because I can't find anyone online with this specific issue. Thanks.

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[Roberam]

OK just tested it with the CD player and RCA to audio jack cord, still same result. I can hear faint sound from the CD playing so I think I might have a grounding issue. It's the only other possible problem I can think of unless the amp itself is bad. I'm going to try and find a different grounding point and I'll post back with the results.

 

[Roberam]

Just finished re locating the amp to the trunk and trying two different grounding points. Same result each time, so I hooked up my 6x9's directly to the head unit and it turns out they aren't blown, despite the smoke that came from them when I first ran them through the amp. So really I'm at a loss, guess the amp must be bad. Has anyone ever experienced these problems before? If so was if fixable or did you just get a new amp?