I reflowed the PCB and left out 4 PGA2500's leaving hopfuly 4 channel preamps for testing.
I found 2 traces missing and fixed them with bodge wires ! one was leaving 2 ic's without sclk ! numero uno IC was missing a -5v supply for digital. The sclk error came about by spelling sclk 'slck' on a few connections in the scematic. the other missing -5v supply , not sure, I think it was just one of those quirky Circuit maker errors on the drawing ..
Anyway, now the last IC in the row is overheating fairly quickly. I took one off leaving three and then the third IC overheats !!!
Not sure what is causing that yet. The -5v is more like -5.4v from the Murata dual power supply which is very near the absolute limit of the pga2500's. not sure if that is the problem.
There could be a bridge somewhere although I cant see one yet.. It does'nt appear as if htere is a short circuit though..
anyway , for now here is a pic of the the setup..
arduino / usb shield 2.0 ( top left ). phantom power module from my other project phantom48 ( middle left) dual +-5v power supply ( bottom left )