Kubicki Active problem

[CyberBass]

I was changing the batteries on my kubicki Ex Factor this afternoon and started playing when then sound started to faff about and fade out bit like an amp makes when you switch it off. I opened the back to check connections and they were fine. I then swapped for another 2 batteries and it started to work for about a minute and then did the same thing. I turned the dial to passive and it plays fine, but when I select the active channels it doesn't work. I need to get this sorted as I am playing a festival on thursday and rely on my active settings. I live in Bristol, what could it be and more importantly is there someone in Bristol that could fix it at such short notice?

Regards
Ade
07970 719252