cdj-850 no sound being output

One of my CDJ-850s started to distort and then lost sound completely!

I turned it off for a while and went back to it later and the sound started coming out again 'sporadically' and distorted until it 'went' again. I have been searching high and low (googling) to try and find the cause and a remedy but continue to draw a blank!

I thought it might be the actual rca connections on the back of the unit that were faulty so had them replaced, to no avail. The only thing I can think of now is that the problem is a faulty 'output board' or 'ribbon cable'?

Please advise....