cross fader or cable djm 600

I have no sound coming out of  my mixer

I switched the 4th pot out with the main volume pot and still the same thing

there are no lights on the level meter

could it be the cable? with both of the diffrent pots connected there was a crackle/rough bit on the lower third of the pots that would send a noise out making me think the cable could be the issue

It may be the cross fader?

Ive cleaned everything and no luck there.

When I turn  up all the levels and amp I can get sound out, poor sound but still sound and it dosent matter where the cross fader is it wont cut the sound out. I think that this is pretty odd that a signal can still get through.

Any ideas - id rather try and fix it myself as it a few years old now