I have the same problem (but on the right channel) with the sam mixer. Did you find a solution?
Headphone cue channel broken on DJM-250
DJM - 250
Channel One headphone button won't light up or opperate when the button is pressed so i can't cue the left channel at all although the channel itself works fine and when the mixer is turned on all lights are functioning.
Is this a motherboard issue or perhaps a fuse? Can any one help?