DJM 800 send problem

I want to use my boss DD7 delay pedal as a send effect, coming back into a channel. 

So I go from the send output on the back of the mixer, into the delay unit. Out from the delay unit, into a free channel, so that I can apply filtering, EQ and use the faders on the delayed signal. And of course, set the Pioneer effects to Snd/Rtn mode.

The problem is that I can't control how much gets sent to the delay unit. Both the depth knob and the on/off button have no effect on the amount of signal being sent, it remains the same. 

Is my mixer faulty or is there really no way to control the level being sent from the mixer?

Thanks in advance, I hope the solution isn't too obvious.