no output from av1 &av2 on pace sky box?

I have just replaced 2 of my original model sky boxes. I had a second tv in another room connected to the av1 port at rear of reciever which allowed me to watch the same channel in that room but since changing the box there is no signal to the second tv.
I have changed the reciever with another that is installed in another room and that won't work either. I have checked as best I can the wiring(which has not been disturbed). Is there a way of checking the output or re-booting the output?