first things first.

your CDJ200s have a headphone input at the back. plug your phones into them and play a track. you should hear it in the phones. there's a volume knob right next to it, which is specifically for the headphone volume, so make sure it isn't all the way down when you try this.

now, once you have eleminated the possibility of it being the CDJ, go to the mixer.

connect your CDJs to the CD inputs. you will notice the cables align vertically, not horizontally. your channel gains/trim should be at 12 o'clock or so. now, plug your headpones into the mixer, set the headphone volume at about 10 o'clock or so. in any case, if there is sound coming out of the CDJ, the level lights should be lighting up.

try pressing the different cue buttons you have on the left side of the mixer to see if you can get any sound out of it.

if your CDJs are good, but none of the above works for the mixer, then the mixer is definitely the problem.

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check out my guest mix for OndaSonora Podcast (aug.2009)