[mab780]

That's very interesting LDS. I hadn't heard of problems like that before.

I will check both of the PSU's before going any further.

To be honest, I don't think that is the problem here because I have swapped the supplies between the Main unit and a 16 channel fader pack and both PSU's work with the fader pack perfectly, suggesting that the fault is not with the PSU at all.

I will run the check though, just to make absolutely sure.
Thanks again.