I have a simple stereo

Question

I have a simple stereo speaker from Radio Shack. Small metal case with two wire input latches. Each box has two speakers in side. Both speakers boxes went out at the same time. I wasn't there when this happened. I hooked the speakers up to a boom box. No output. Internally everything looks okay. The only electrical component I can see is an electrolytic capacitor. It looks intact. The resistance across the input read infinity. Any hints?