'Broken' amp started working when I boosted my car
 

So i have a 600W 4 channel pioneer amp that suddenly died and stopped powering my four speakers a while back. I brought it in and a guy who knows what he's doing tested it with a machine, checked out wiring and came to the conclusion that the amp is dead. Recently my battery died and after getting boosted, the amp started working for about a day, and while listening to music it cut out again. Brought it back and he told me the same thing. Amp is dead, and he's not sure why it worked for a bit but just told me its an amp issue.

SO, whats going on? What are the possible problems and possible solutions. I bought a replacement amp before it randomly started working again and I'm considering just swapping the amp, but I dont want to waste a good amp either.

Thanks a lot.

You aren't giving us much to work on, but perhaps the amp power connection to the battery is not solid. When boosting you put the clamps on the battery positive terminal and perhaps this fixed the connection temporarily.
When the connection is poor, it may not show up in a voltage test. If you test for 12 volts at the amp terminal all is good, but when the amp turns on and draws current, the poor battery connection causes a voltage drop.

Have you tried to measure voltage across the amp pos and neg terminals at the amp, with the amp ON?