You could power off the shelves, don’t need them until you have an A on processor
Power off processor, reseat the DSCXL (it’s hot swappable but in this case I would power off). Reseat RTM on the back, and MCM module.
Try your backup CF card
With correct v24 cable you can get more info from service port,38400 8 n 1 (I think)
It will flash an error code on processor after 01, 4 more digits, when it reboots.