Please Help - amp pop, shut down

I am having trouble with my subwoofer. I am posting this thread here because I think the problem is in my amp. Sorry if I am posting in the wrong area.
A brief description of my dilemna, after my sub has been on a few minutes, it makes a popping noise and shuts down (I believe into a protection mode). It will not come back on for about 15-30 minutes. Then, I get to go thru the whole frustrating experience again.
Unfortunately, I am not very experienced with troubleshooting amplifiers. I only know enough about electronics to get myself into trouble. I also am quite poor at the current time and cannot afford to have it professionally serviced. This leaves me trying to fix this thing myself.
Would someone be willing to suggest where I should begin to troubleshoot? Any help would be greatly appreciated...
I have visually checked the components and solder joints on the amp plate under a magnifier. All appear to be in good shape. I have checked the resistor and cap that are bridged across the active woofer and they also checked fine.
Please, please, please help me...