What part(s) of the amp should I check, And how do I go about checking them? Make sure the power light is on etc. Also, you can put the multimeter leads in the amplifer's speaker outputs, set it to AC voltage, and play some music. If it is getting a changing voltage (unless its a test tone) the amp should be fine. To test the woofer, take it out and test each of the coils and see if the resistance is close to what it should be.