Is the SC189L accessible when powered up?
It's pretty much a sure thing that the SC189 purpose in life is generating the so-called 1.8V DC "core-voltage" to the processor chip (TMS320F28015). Without its core voltage, the processor chip is dead.
From the SC189 datasheet you can see the VIN and VOUT pins on the regulator chip. The circuit is most likely that shown in the "typical application circuit" albeit they show the 1.2V version. It would take some close quarters probing but you'd only need a meter (as opposed to an oscilloscope), steady-hands, and good eyesight.
