Yaskawa 616G3 flatline

I have a Yaskawa 616G3 7.5 HP inverter that is flatline too. After downloading hundreds of pages from Yaskawa's web site I keep hitting a dead end regarding the Power Control Board (PCB1) .... It fails to give anything but basic info for tracking the 24vdc and 15vdc enable
All the power electronics read OK and I get the proper voltage on the DC buss ... no blown fuse's ... thermal overtemp is ok.
I tried backfeeding an external 24vdc supply from the cooling fan and it did give me voltage between 1-11 but no 15vdc between 15-17

I can only suggest tracing the circuit back from pin 15, its likely to come from a regulator chip (24V -> 15V). Then you have a handle on the internal +24V line, which again could come from another chip. can't you find any bridge rectifier/large electrolytic/power transformer and check for voltages?
Frank