I have a spare PSU, changed the PCI-E power cable and PSU both.
System up and running now.
However monitoring the PSU temp (hand behind the exhaust vents) seems to be very hot. Don't have a laser temp gun, so cannot tell, but seems very hot to hand. 1500W PSU should take the load of 4 r9 290 cards (230W each), can any one comment on the built quality of this brand of PSU please.
PSU: Silverstone Strider Series 1500 Watt (SST-ST1500)